qemu/linux-user/signal.c

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/*
* Emulation of Linux signals
*
* Copyright (c) 2003 Fabrice Bellard
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include "qemu/osdep.h"
#include "qemu/bitops.h"
#include "gdbstub/user.h"
#include "hw/core/tcg-cpu-ops.h"
#include <sys/ucontext.h>
#include <sys/resource.h>
#include "qemu.h"
#include "user-internals.h"
#include "strace.h"
#include "loader.h"
#include "trace.h"
#include "signal-common.h"
#include "host-signal.h"
#include "user/safe-syscall.h"
#include "tcg/tcg.h"
static struct target_sigaction sigact_table[TARGET_NSIG];
static void host_signal_handler(int host_signum, siginfo_t *info,
void *puc);
/* Fallback addresses into sigtramp page. */
abi_ulong default_sigreturn;
abi_ulong default_rt_sigreturn;
/*
* System includes define _NSIG as SIGRTMAX + 1, but qemu (like the kernel)
* defines TARGET_NSIG as TARGET_SIGRTMAX and the first signal is 1.
* Signal number 0 is reserved for use as kill(pid, 0), to test whether
* a process exists without sending it a signal.
*/
#ifdef __SIGRTMAX
QEMU_BUILD_BUG_ON(__SIGRTMAX + 1 != _NSIG);
#endif
static uint8_t host_to_target_signal_table[_NSIG] = {
#define MAKE_SIG_ENTRY(sig) [sig] = TARGET_##sig,
MAKE_SIGNAL_LIST
#undef MAKE_SIG_ENTRY
};
static uint8_t target_to_host_signal_table[TARGET_NSIG + 1];
/* valid sig is between 1 and _NSIG - 1 */
int host_to_target_signal(int sig)
{
if (sig < 1) {
return sig;
}
if (sig >= _NSIG) {
return TARGET_NSIG + 1;
}
return host_to_target_signal_table[sig];
}
/* valid sig is between 1 and TARGET_NSIG */
int target_to_host_signal(int sig)
{
if (sig < 1) {
return sig;
}
if (sig > TARGET_NSIG) {
return _NSIG;
}
return target_to_host_signal_table[sig];
}
static inline void target_sigaddset(target_sigset_t *set, int signum)
{
signum--;
abi_ulong mask = (abi_ulong)1 << (signum % TARGET_NSIG_BPW);
set->sig[signum / TARGET_NSIG_BPW] |= mask;
}
static inline int target_sigismember(const target_sigset_t *set, int signum)
{
signum--;
abi_ulong mask = (abi_ulong)1 << (signum % TARGET_NSIG_BPW);
return ((set->sig[signum / TARGET_NSIG_BPW] & mask) != 0);
}
void host_to_target_sigset_internal(target_sigset_t *d,
const sigset_t *s)
{
int host_sig, target_sig;
target_sigemptyset(d);
for (host_sig = 1; host_sig < _NSIG; host_sig++) {
target_sig = host_to_target_signal(host_sig);
if (target_sig < 1 || target_sig > TARGET_NSIG) {
continue;
}
if (sigismember(s, host_sig)) {
target_sigaddset(d, target_sig);
}
}
}
void host_to_target_sigset(target_sigset_t *d, const sigset_t *s)
{
target_sigset_t d1;
int i;
host_to_target_sigset_internal(&d1, s);
for(i = 0;i < TARGET_NSIG_WORDS; i++)
d->sig[i] = tswapal(d1.sig[i]);
}
void target_to_host_sigset_internal(sigset_t *d,
const target_sigset_t *s)
{
int host_sig, target_sig;
sigemptyset(d);
for (target_sig = 1; target_sig <= TARGET_NSIG; target_sig++) {
host_sig = target_to_host_signal(target_sig);
if (host_sig < 1 || host_sig >= _NSIG) {
continue;
}
if (target_sigismember(s, target_sig)) {
sigaddset(d, host_sig);
}
}
}
void target_to_host_sigset(sigset_t *d, const target_sigset_t *s)
{
target_sigset_t s1;
int i;
for(i = 0;i < TARGET_NSIG_WORDS; i++)
s1.sig[i] = tswapal(s->sig[i]);
target_to_host_sigset_internal(d, &s1);
}
void host_to_target_old_sigset(abi_ulong *old_sigset,
const sigset_t *sigset)
{
target_sigset_t d;
host_to_target_sigset(&d, sigset);
*old_sigset = d.sig[0];
}
void target_to_host_old_sigset(sigset_t *sigset,
const abi_ulong *old_sigset)
{
target_sigset_t d;
int i;
d.sig[0] = *old_sigset;
for(i = 1;i < TARGET_NSIG_WORDS; i++)
d.sig[i] = 0;
target_to_host_sigset(sigset, &d);
}
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
int block_signals(void)
{
TaskState *ts = (TaskState *)thread_cpu->opaque;
sigset_t set;
/* It's OK to block everything including SIGSEGV, because we won't
* run any further guest code before unblocking signals in
* process_pending_signals().
*/
sigfillset(&set);
sigprocmask(SIG_SETMASK, &set, 0);
return qatomic_xchg(&ts->signal_pending, 1);
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
}
/* Wrapper for sigprocmask function
* Emulates a sigprocmask in a safe way for the guest. Note that set and oldset
* are host signal set, not guest ones. Returns -QEMU_ERESTARTSYS if
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
* a signal was already pending and the syscall must be restarted, or
* 0 on success.
* If set is NULL, this is guaranteed not to fail.
*/
int do_sigprocmask(int how, const sigset_t *set, sigset_t *oldset)
{
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
TaskState *ts = (TaskState *)thread_cpu->opaque;
if (oldset) {
*oldset = ts->signal_mask;
}
if (set) {
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
int i;
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
if (block_signals()) {
return -QEMU_ERESTARTSYS;
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
}
switch (how) {
case SIG_BLOCK:
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
sigorset(&ts->signal_mask, &ts->signal_mask, set);
break;
case SIG_UNBLOCK:
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
for (i = 1; i <= NSIG; ++i) {
if (sigismember(set, i)) {
sigdelset(&ts->signal_mask, i);
}
}
break;
case SIG_SETMASK:
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
ts->signal_mask = *set;
break;
default:
g_assert_not_reached();
}
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
/* Silently ignore attempts to change blocking status of KILL or STOP */
sigdelset(&ts->signal_mask, SIGKILL);
sigdelset(&ts->signal_mask, SIGSTOP);
}
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
return 0;
}
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
/* Just set the guest's signal mask to the specified value; the
* caller is assumed to have called block_signals() already.
*/
void set_sigmask(const sigset_t *set)
{
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
TaskState *ts = (TaskState *)thread_cpu->opaque;
ts->signal_mask = *set;
}
/* sigaltstack management */
int on_sig_stack(unsigned long sp)
{
TaskState *ts = (TaskState *)thread_cpu->opaque;
return (sp - ts->sigaltstack_used.ss_sp
< ts->sigaltstack_used.ss_size);
}
int sas_ss_flags(unsigned long sp)
{
TaskState *ts = (TaskState *)thread_cpu->opaque;
return (ts->sigaltstack_used.ss_size == 0 ? SS_DISABLE
: on_sig_stack(sp) ? SS_ONSTACK : 0);
}
abi_ulong target_sigsp(abi_ulong sp, struct target_sigaction *ka)
{
/*
* This is the X/Open sanctioned signal stack switching.
*/
TaskState *ts = (TaskState *)thread_cpu->opaque;
if ((ka->sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp)) {
return ts->sigaltstack_used.ss_sp + ts->sigaltstack_used.ss_size;
}
return sp;
}
void target_save_altstack(target_stack_t *uss, CPUArchState *env)
{
TaskState *ts = (TaskState *)thread_cpu->opaque;
__put_user(ts->sigaltstack_used.ss_sp, &uss->ss_sp);
__put_user(sas_ss_flags(get_sp_from_cpustate(env)), &uss->ss_flags);
__put_user(ts->sigaltstack_used.ss_size, &uss->ss_size);
}
abi_long target_restore_altstack(target_stack_t *uss, CPUArchState *env)
{
TaskState *ts = (TaskState *)thread_cpu->opaque;
size_t minstacksize = TARGET_MINSIGSTKSZ;
target_stack_t ss;
#if defined(TARGET_PPC64)
/* ELF V2 for PPC64 has a 4K minimum stack size for signal handlers */
struct image_info *image = ts->info;
if (get_ppc64_abi(image) > 1) {
minstacksize = 4096;
}
#endif
__get_user(ss.ss_sp, &uss->ss_sp);
__get_user(ss.ss_size, &uss->ss_size);
__get_user(ss.ss_flags, &uss->ss_flags);
if (on_sig_stack(get_sp_from_cpustate(env))) {
return -TARGET_EPERM;
}
switch (ss.ss_flags) {
default:
return -TARGET_EINVAL;
case TARGET_SS_DISABLE:
ss.ss_size = 0;
ss.ss_sp = 0;
break;
case TARGET_SS_ONSTACK:
case 0:
if (ss.ss_size < minstacksize) {
return -TARGET_ENOMEM;
}
break;
}
ts->sigaltstack_used.ss_sp = ss.ss_sp;
ts->sigaltstack_used.ss_size = ss.ss_size;
return 0;
}
/* siginfo conversion */
static inline void host_to_target_siginfo_noswap(target_siginfo_t *tinfo,
const siginfo_t *info)
{
int sig = host_to_target_signal(info->si_signo);
int si_code = info->si_code;
int si_type;
tinfo->si_signo = sig;
tinfo->si_errno = 0;
tinfo->si_code = info->si_code;
/* This memset serves two purposes:
* (1) ensure we don't leak random junk to the guest later
* (2) placate false positives from gcc about fields
* being used uninitialized if it chooses to inline both this
* function and tswap_siginfo() into host_to_target_siginfo().
*/
memset(tinfo->_sifields._pad, 0, sizeof(tinfo->_sifields._pad));
/* This is awkward, because we have to use a combination of
* the si_code and si_signo to figure out which of the union's
* members are valid. (Within the host kernel it is always possible
* to tell, but the kernel carefully avoids giving userspace the
* high 16 bits of si_code, so we don't have the information to
* do this the easy way...) We therefore make our best guess,
* bearing in mind that a guest can spoof most of the si_codes
* via rt_sigqueueinfo() if it likes.
*
* Once we have made our guess, we record it in the top 16 bits of
* the si_code, so that tswap_siginfo() later can use it.
* tswap_siginfo() will strip these top bits out before writing
* si_code to the guest (sign-extending the lower bits).
*/
switch (si_code) {
case SI_USER:
case SI_TKILL:
case SI_KERNEL:
/* Sent via kill(), tkill() or tgkill(), or direct from the kernel.
* These are the only unspoofable si_code values.
*/
tinfo->_sifields._kill._pid = info->si_pid;
tinfo->_sifields._kill._uid = info->si_uid;
si_type = QEMU_SI_KILL;
break;
default:
/* Everything else is spoofable. Make best guess based on signal */
switch (sig) {
case TARGET_SIGCHLD:
tinfo->_sifields._sigchld._pid = info->si_pid;
tinfo->_sifields._sigchld._uid = info->si_uid;
linux-user/signal: Map exit signals in SIGCHLD siginfo_t When converting a siginfo_t from waitid(), the interpretation of si_status depends on the value of si_code: For CLD_EXITED, it is an exit code and should be copied verbatim. For other codes, it is a signal number (possibly with additional high bits from ptrace) that should be mapped. This code was previously changed in commit 1c3dfb506ea3 ("linux-user/signal: Decode waitid si_code"), but the fix was incomplete. Tested with the following test program: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/wait.h> int main() { pid_t pid = fork(); if (pid == 0) { exit(12); } else { siginfo_t siginfo = {}; waitid(P_PID, pid, &siginfo, WEXITED); printf("Code: %d, status: %d\n", (int)siginfo.si_code, (int)siginfo.si_status); } pid = fork(); if (pid == 0) { raise(SIGUSR2); } else { siginfo_t siginfo = {}; waitid(P_PID, pid, &siginfo, WEXITED); printf("Code: %d, status: %d\n", (int)siginfo.si_code, (int)siginfo.si_status); } } Output with an x86_64 host and mips64el target before 1c3dfb506ea3 (incorrect: exit code 12 is translated like a signal): Code: 1, status: 17 Code: 2, status: 17 After 1c3dfb506ea3 (incorrect: signal number is not translated): Code: 1, status: 12 Code: 2, status: 12 With this patch: Code: 1, status: 12 Code: 2, status: 17 Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net> Reviewed-by: Laurent Vivier <laurent@vivier.eu> Message-Id: <81534fde7cdfc6acea4889d886fbefdd606630fb.1635019124.git.mschiffer@universe-factory.net> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
2021-10-23 22:59:10 +03:00
if (si_code == CLD_EXITED)
tinfo->_sifields._sigchld._status = info->si_status;
else
tinfo->_sifields._sigchld._status
= host_to_target_signal(info->si_status & 0x7f)
| (info->si_status & ~0x7f);
tinfo->_sifields._sigchld._utime = info->si_utime;
tinfo->_sifields._sigchld._stime = info->si_stime;
si_type = QEMU_SI_CHLD;
break;
case TARGET_SIGIO:
tinfo->_sifields._sigpoll._band = info->si_band;
tinfo->_sifields._sigpoll._fd = info->si_fd;
si_type = QEMU_SI_POLL;
break;
default:
/* Assume a sigqueue()/mq_notify()/rt_sigqueueinfo() source. */
tinfo->_sifields._rt._pid = info->si_pid;
tinfo->_sifields._rt._uid = info->si_uid;
/* XXX: potential problem if 64 bit */
tinfo->_sifields._rt._sigval.sival_ptr
= (abi_ulong)(unsigned long)info->si_value.sival_ptr;
si_type = QEMU_SI_RT;
break;
}
break;
}
tinfo->si_code = deposit32(si_code, 16, 16, si_type);
}
void tswap_siginfo(target_siginfo_t *tinfo,
const target_siginfo_t *info)
{
int si_type = extract32(info->si_code, 16, 16);
int si_code = sextract32(info->si_code, 0, 16);
__put_user(info->si_signo, &tinfo->si_signo);
__put_user(info->si_errno, &tinfo->si_errno);
__put_user(si_code, &tinfo->si_code);
/* We can use our internal marker of which fields in the structure
* are valid, rather than duplicating the guesswork of
* host_to_target_siginfo_noswap() here.
*/
switch (si_type) {
case QEMU_SI_KILL:
__put_user(info->_sifields._kill._pid, &tinfo->_sifields._kill._pid);
__put_user(info->_sifields._kill._uid, &tinfo->_sifields._kill._uid);
break;
case QEMU_SI_TIMER:
__put_user(info->_sifields._timer._timer1,
&tinfo->_sifields._timer._timer1);
__put_user(info->_sifields._timer._timer2,
&tinfo->_sifields._timer._timer2);
break;
case QEMU_SI_POLL:
__put_user(info->_sifields._sigpoll._band,
&tinfo->_sifields._sigpoll._band);
__put_user(info->_sifields._sigpoll._fd,
&tinfo->_sifields._sigpoll._fd);
break;
case QEMU_SI_FAULT:
__put_user(info->_sifields._sigfault._addr,
&tinfo->_sifields._sigfault._addr);
break;
case QEMU_SI_CHLD:
__put_user(info->_sifields._sigchld._pid,
&tinfo->_sifields._sigchld._pid);
__put_user(info->_sifields._sigchld._uid,
&tinfo->_sifields._sigchld._uid);
__put_user(info->_sifields._sigchld._status,
&tinfo->_sifields._sigchld._status);
__put_user(info->_sifields._sigchld._utime,
&tinfo->_sifields._sigchld._utime);
__put_user(info->_sifields._sigchld._stime,
&tinfo->_sifields._sigchld._stime);
break;
case QEMU_SI_RT:
__put_user(info->_sifields._rt._pid, &tinfo->_sifields._rt._pid);
__put_user(info->_sifields._rt._uid, &tinfo->_sifields._rt._uid);
__put_user(info->_sifields._rt._sigval.sival_ptr,
&tinfo->_sifields._rt._sigval.sival_ptr);
break;
default:
g_assert_not_reached();
}
}
void host_to_target_siginfo(target_siginfo_t *tinfo, const siginfo_t *info)
{
target_siginfo_t tgt_tmp;
host_to_target_siginfo_noswap(&tgt_tmp, info);
tswap_siginfo(tinfo, &tgt_tmp);
}
/* XXX: we support only POSIX RT signals are used. */
/* XXX: find a solution for 64 bit (additional malloced data is needed) */
void target_to_host_siginfo(siginfo_t *info, const target_siginfo_t *tinfo)
{
/* This conversion is used only for the rt_sigqueueinfo syscall,
* and so we know that the _rt fields are the valid ones.
*/
abi_ulong sival_ptr;
__get_user(info->si_signo, &tinfo->si_signo);
__get_user(info->si_errno, &tinfo->si_errno);
__get_user(info->si_code, &tinfo->si_code);
__get_user(info->si_pid, &tinfo->_sifields._rt._pid);
__get_user(info->si_uid, &tinfo->_sifields._rt._uid);
__get_user(sival_ptr, &tinfo->_sifields._rt._sigval.sival_ptr);
info->si_value.sival_ptr = (void *)(long)sival_ptr;
}
/* returns 1 if given signal should dump core if not handled */
static int core_dump_signal(int sig)
{
switch (sig) {
case TARGET_SIGABRT:
case TARGET_SIGFPE:
case TARGET_SIGILL:
case TARGET_SIGQUIT:
case TARGET_SIGSEGV:
case TARGET_SIGTRAP:
case TARGET_SIGBUS:
return (1);
default:
return (0);
}
}
static void signal_table_init(void)
{
int hsig, tsig, count;
/*
* Signals are supported starting from TARGET_SIGRTMIN and going up
* until we run out of host realtime signals. Glibc uses the lower 2
* RT signals and (hopefully) nobody uses the upper ones.
* This is why SIGRTMIN (34) is generally greater than __SIGRTMIN (32).
* To fix this properly we would need to do manual signal delivery
* multiplexed over a single host signal.
* Attempts for configure "missing" signals via sigaction will be
* silently ignored.
*
* Remap the target SIGABRT, so that we can distinguish host abort
* from guest abort. When the guest registers a signal handler or
* calls raise(SIGABRT), the host will raise SIG_RTn. If the guest
* arrives at dump_core_and_abort(), we will map back to host SIGABRT
* so that the parent (native or emulated) sees the correct signal.
* Finally, also map host to guest SIGABRT so that the emulated
* parent sees the correct mapping from wait status.
*/
hsig = SIGRTMIN;
host_to_target_signal_table[SIGABRT] = 0;
host_to_target_signal_table[hsig++] = TARGET_SIGABRT;
for (tsig = TARGET_SIGRTMIN;
hsig <= SIGRTMAX && tsig <= TARGET_NSIG;
hsig++, tsig++) {
host_to_target_signal_table[hsig] = tsig;
}
/* Invert the mapping that has already been assigned. */
for (hsig = 1; hsig < _NSIG; hsig++) {
tsig = host_to_target_signal_table[hsig];
if (tsig) {
assert(target_to_host_signal_table[tsig] == 0);
target_to_host_signal_table[tsig] = hsig;
}
}
host_to_target_signal_table[SIGABRT] = TARGET_SIGABRT;
/* Map everything else out-of-bounds. */
for (hsig = 1; hsig < _NSIG; hsig++) {
if (host_to_target_signal_table[hsig] == 0) {
host_to_target_signal_table[hsig] = TARGET_NSIG + 1;
}
}
for (count = 0, tsig = 1; tsig <= TARGET_NSIG; tsig++) {
if (target_to_host_signal_table[tsig] == 0) {
target_to_host_signal_table[tsig] = _NSIG;
count++;
}
}
trace_signal_table_init(count);
}
void signal_init(void)
{
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
TaskState *ts = (TaskState *)thread_cpu->opaque;
struct sigaction act, oact;
/* initialize signal conversion tables */
signal_table_init();
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
/* Set the signal mask from the host mask. */
sigprocmask(0, 0, &ts->signal_mask);
sigfillset(&act.sa_mask);
act.sa_flags = SA_SIGINFO;
act.sa_sigaction = host_signal_handler;
/*
* A parent process may configure ignored signals, but all other
* signals are default. For any target signals that have no host
* mapping, set to ignore. For all core_dump_signal, install our
* host signal handler so that we may invoke dump_core_and_abort.
* This includes SIGSEGV and SIGBUS, which are also need our signal
* handler for paging and exceptions.
*/
for (int tsig = 1; tsig <= TARGET_NSIG; tsig++) {
int hsig = target_to_host_signal(tsig);
abi_ptr thand = TARGET_SIG_IGN;
if (hsig >= _NSIG) {
continue;
}
/* As we force remap SIGABRT, cannot probe and install in one step. */
if (tsig == TARGET_SIGABRT) {
sigaction(SIGABRT, NULL, &oact);
sigaction(hsig, &act, NULL);
} else {
struct sigaction *iact = core_dump_signal(tsig) ? &act : NULL;
sigaction(hsig, iact, &oact);
}
if (oact.sa_sigaction != (void *)SIG_IGN) {
thand = TARGET_SIG_DFL;
}
sigact_table[tsig - 1]._sa_handler = thand;
}
}
/* Force a synchronously taken signal. The kernel force_sig() function
* also forces the signal to "not blocked, not ignored", but for QEMU
* that work is done in process_pending_signals().
*/
void force_sig(int sig)
{
CPUState *cpu = thread_cpu;
CPUArchState *env = cpu_env(cpu);
target_siginfo_t info = {};
info.si_signo = sig;
info.si_errno = 0;
info.si_code = TARGET_SI_KERNEL;
info._sifields._kill._pid = 0;
info._sifields._kill._uid = 0;
queue_signal(env, info.si_signo, QEMU_SI_KILL, &info);
}
/*
* Force a synchronously taken QEMU_SI_FAULT signal. For QEMU the
* 'force' part is handled in process_pending_signals().
*/
void force_sig_fault(int sig, int code, abi_ulong addr)
{
CPUState *cpu = thread_cpu;
CPUArchState *env = cpu_env(cpu);
target_siginfo_t info = {};
info.si_signo = sig;
info.si_errno = 0;
info.si_code = code;
info._sifields._sigfault._addr = addr;
queue_signal(env, sig, QEMU_SI_FAULT, &info);
}
/* Force a SIGSEGV if we couldn't write to memory trying to set
* up the signal frame. oldsig is the signal we were trying to handle
* at the point of failure.
*/
#if !defined(TARGET_RISCV)
void force_sigsegv(int oldsig)
{
if (oldsig == SIGSEGV) {
/* Make sure we don't try to deliver the signal again; this will
* end up with handle_pending_signal() calling dump_core_and_abort().
*/
sigact_table[oldsig - 1]._sa_handler = TARGET_SIG_DFL;
}
force_sig(TARGET_SIGSEGV);
}
#endif
void cpu_loop_exit_sigsegv(CPUState *cpu, target_ulong addr,
MMUAccessType access_type, bool maperr, uintptr_t ra)
{
const struct TCGCPUOps *tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops;
if (tcg_ops->record_sigsegv) {
tcg_ops->record_sigsegv(cpu, addr, access_type, maperr, ra);
}
force_sig_fault(TARGET_SIGSEGV,
maperr ? TARGET_SEGV_MAPERR : TARGET_SEGV_ACCERR,
addr);
cpu->exception_index = EXCP_INTERRUPT;
cpu_loop_exit_restore(cpu, ra);
}
void cpu_loop_exit_sigbus(CPUState *cpu, target_ulong addr,
MMUAccessType access_type, uintptr_t ra)
{
const struct TCGCPUOps *tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops;
if (tcg_ops->record_sigbus) {
tcg_ops->record_sigbus(cpu, addr, access_type, ra);
}
force_sig_fault(TARGET_SIGBUS, TARGET_BUS_ADRALN, addr);
cpu->exception_index = EXCP_INTERRUPT;
cpu_loop_exit_restore(cpu, ra);
}
/* abort execution with signal */
static G_NORETURN
void die_with_signal(int host_sig)
{
struct sigaction act = {
.sa_handler = SIG_DFL,
};
/*
* The proper exit code for dying from an uncaught signal is -<signal>.
* The kernel doesn't allow exit() or _exit() to pass a negative value.
* To get the proper exit code we need to actually die from an uncaught
* signal. Here the default signal handler is installed, we send
* the signal and we wait for it to arrive.
*/
sigfillset(&act.sa_mask);
sigaction(host_sig, &act, NULL);
kill(getpid(), host_sig);
/* Make sure the signal isn't masked (reusing the mask inside of act). */
sigdelset(&act.sa_mask, host_sig);
sigsuspend(&act.sa_mask);
/* unreachable */
_exit(EXIT_FAILURE);
}
static G_NORETURN
void dump_core_and_abort(CPUArchState *env, int target_sig)
{
CPUState *cpu = env_cpu(env);
TaskState *ts = (TaskState *)cpu->opaque;
int host_sig, core_dumped = 0;
/* On exit, undo the remapping of SIGABRT. */
if (target_sig == TARGET_SIGABRT) {
host_sig = SIGABRT;
} else {
host_sig = target_to_host_signal(target_sig);
}
trace_user_dump_core_and_abort(env, target_sig, host_sig);
gdb_signalled(env, target_sig);
/* dump core if supported by target binary format */
if (core_dump_signal(target_sig) && (ts->bprm->core_dump != NULL)) {
stop_all_tasks();
core_dumped =
((*ts->bprm->core_dump)(target_sig, env) == 0);
}
if (core_dumped) {
/* we already dumped the core of target process, we don't want
* a coredump of qemu itself */
struct rlimit nodump;
getrlimit(RLIMIT_CORE, &nodump);
nodump.rlim_cur=0;
setrlimit(RLIMIT_CORE, &nodump);
(void) fprintf(stderr, "qemu: uncaught target signal %d (%s) - %s\n",
target_sig, strsignal(host_sig), "core dumped" );
}
preexit_cleanup(env, 128 + target_sig);
die_with_signal(host_sig);
}
/* queue a signal so that it will be send to the virtual CPU as soon
as possible */
void queue_signal(CPUArchState *env, int sig, int si_type,
target_siginfo_t *info)
{
CPUState *cpu = env_cpu(env);
TaskState *ts = cpu->opaque;
trace_user_queue_signal(env, sig);
info->si_code = deposit32(info->si_code, 16, 16, si_type);
ts->sync_signal.info = *info;
ts->sync_signal.pending = sig;
/* signal that a new signal is pending */
qatomic_set(&ts->signal_pending, 1);
}
/* Adjust the signal context to rewind out of safe-syscall if we're in it */
linux-user: Provide safe_syscall for fixing races between signals and syscalls If a signal is delivered immediately before a blocking system call the handler will only be called after the system call returns, which may be a long time later or never. This is fixed by using a function (safe_syscall) that checks if a guest signal is pending prior to making a system call, and if so does not call the system call and returns -TARGET_ERESTARTSYS. If a signal is received between the check and the system call host_signal_handler() rewinds execution to before the check. This rewinding has the effect of closing the race window so that safe_syscall will reliably either (a) go into the host syscall with no unprocessed guest signals pending or or (b) return -TARGET_ERESTARTSYS so that the caller can deal with the signals. Implementing this requires a per-host-architecture assembly language fragment. This will also resolve the mishandling of the SA_RESTART flag where we would restart a host system call and not call the guest signal handler until the syscall finally completed -- syscall restarting now always happens at the guest syscall level so the guest signal handler will run. (The host syscall will never be restarted because if the host kernel rewinds the PC to point at the syscall insn for a restart then our host_signal_handler() will see this and arrange the guest PC rewind.) This commit contains the infrastructure for implementing safe_syscall and the assembly language fragment for x86-64, but does not change any syscalls to use it. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-14-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: * Avoid having an architecture if-ladder in configure by putting linux-user/host/$(ARCH) on the include path and including safe-syscall.inc.S from it * Avoid ifdef ladder in signal.c by creating new hostdep.h to hold host-architecture-specific things * Added copyright/license header to safe-syscall.inc.S * Rewrote commit message * Added comments to safe-syscall.inc.S * Changed calling convention of safe_syscall() to match syscall() (returns -1 and host error in errno on failure) * Added a long comment in qemu.h about how to use safe_syscall() to implement guest syscalls. ] RV: squashed Peters "fixup! linux-user: compile on non-x86-64 hosts" patch Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2016-05-12 20:47:46 +03:00
static inline void rewind_if_in_safe_syscall(void *puc)
{
host_sigcontext *uc = (host_sigcontext *)puc;
uintptr_t pcreg = host_signal_pc(uc);
if (pcreg > (uintptr_t)safe_syscall_start
&& pcreg < (uintptr_t)safe_syscall_end) {
host_signal_set_pc(uc, (uintptr_t)safe_syscall_start);
}
}
linux-user: Provide safe_syscall for fixing races between signals and syscalls If a signal is delivered immediately before a blocking system call the handler will only be called after the system call returns, which may be a long time later or never. This is fixed by using a function (safe_syscall) that checks if a guest signal is pending prior to making a system call, and if so does not call the system call and returns -TARGET_ERESTARTSYS. If a signal is received between the check and the system call host_signal_handler() rewinds execution to before the check. This rewinding has the effect of closing the race window so that safe_syscall will reliably either (a) go into the host syscall with no unprocessed guest signals pending or or (b) return -TARGET_ERESTARTSYS so that the caller can deal with the signals. Implementing this requires a per-host-architecture assembly language fragment. This will also resolve the mishandling of the SA_RESTART flag where we would restart a host system call and not call the guest signal handler until the syscall finally completed -- syscall restarting now always happens at the guest syscall level so the guest signal handler will run. (The host syscall will never be restarted because if the host kernel rewinds the PC to point at the syscall insn for a restart then our host_signal_handler() will see this and arrange the guest PC rewind.) This commit contains the infrastructure for implementing safe_syscall and the assembly language fragment for x86-64, but does not change any syscalls to use it. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-14-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: * Avoid having an architecture if-ladder in configure by putting linux-user/host/$(ARCH) on the include path and including safe-syscall.inc.S from it * Avoid ifdef ladder in signal.c by creating new hostdep.h to hold host-architecture-specific things * Added copyright/license header to safe-syscall.inc.S * Rewrote commit message * Added comments to safe-syscall.inc.S * Changed calling convention of safe_syscall() to match syscall() (returns -1 and host error in errno on failure) * Added a long comment in qemu.h about how to use safe_syscall() to implement guest syscalls. ] RV: squashed Peters "fixup! linux-user: compile on non-x86-64 hosts" patch Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2016-05-12 20:47:46 +03:00
static G_NORETURN
void die_from_signal(siginfo_t *info)
{
char sigbuf[4], codebuf[12];
const char *sig, *code = NULL;
switch (info->si_signo) {
case SIGSEGV:
sig = "SEGV";
switch (info->si_code) {
case SEGV_MAPERR:
code = "MAPERR";
break;
case SEGV_ACCERR:
code = "ACCERR";
break;
}
break;
case SIGBUS:
sig = "BUS";
switch (info->si_code) {
case BUS_ADRALN:
code = "ADRALN";
break;
case BUS_ADRERR:
code = "ADRERR";
break;
}
break;
case SIGILL:
sig = "ILL";
switch (info->si_code) {
case ILL_ILLOPC:
code = "ILLOPC";
break;
case ILL_ILLOPN:
code = "ILLOPN";
break;
case ILL_ILLADR:
code = "ILLADR";
break;
case ILL_PRVOPC:
code = "PRVOPC";
break;
case ILL_PRVREG:
code = "PRVREG";
break;
case ILL_COPROC:
code = "COPROC";
break;
}
break;
case SIGFPE:
sig = "FPE";
switch (info->si_code) {
case FPE_INTDIV:
code = "INTDIV";
break;
case FPE_INTOVF:
code = "INTOVF";
break;
}
break;
case SIGTRAP:
sig = "TRAP";
break;
default:
snprintf(sigbuf, sizeof(sigbuf), "%d", info->si_signo);
sig = sigbuf;
break;
}
if (code == NULL) {
snprintf(codebuf, sizeof(sigbuf), "%d", info->si_code);
code = codebuf;
}
error_report("QEMU internal SIG%s {code=%s, addr=%p}",
sig, code, info->si_addr);
die_with_signal(info->si_signo);
}
static void host_sigsegv_handler(CPUState *cpu, siginfo_t *info,
host_sigcontext *uc)
{
uintptr_t host_addr = (uintptr_t)info->si_addr;
/*
* Convert forcefully to guest address space: addresses outside
* reserved_va are still valid to report via SEGV_MAPERR.
*/
bool is_valid = h2g_valid(host_addr);
abi_ptr guest_addr = h2g_nocheck(host_addr);
uintptr_t pc = host_signal_pc(uc);
bool is_write = host_signal_write(info, uc);
MMUAccessType access_type = adjust_signal_pc(&pc, is_write);
bool maperr;
/* If this was a write to a TB protected page, restart. */
if (is_write
&& is_valid
&& info->si_code == SEGV_ACCERR
&& handle_sigsegv_accerr_write(cpu, host_signal_mask(uc),
pc, guest_addr)) {
return;
}
/*
* If the access was not on behalf of the guest, within the executable
* mapping of the generated code buffer, then it is a host bug.
*/
if (access_type != MMU_INST_FETCH
&& !in_code_gen_buffer((void *)(pc - tcg_splitwx_diff))) {
die_from_signal(info);
}
maperr = true;
if (is_valid && info->si_code == SEGV_ACCERR) {
/*
* With reserved_va, the whole address space is PROT_NONE,
* which means that we may get ACCERR when we want MAPERR.
*/
if (page_get_flags(guest_addr) & PAGE_VALID) {
maperr = false;
} else {
info->si_code = SEGV_MAPERR;
}
}
sigprocmask(SIG_SETMASK, host_signal_mask(uc), NULL);
cpu_loop_exit_sigsegv(cpu, guest_addr, access_type, maperr, pc);
}
static void host_sigbus_handler(CPUState *cpu, siginfo_t *info,
host_sigcontext *uc)
{
uintptr_t pc = host_signal_pc(uc);
bool is_write = host_signal_write(info, uc);
MMUAccessType access_type = adjust_signal_pc(&pc, is_write);
/*
* If the access was not on behalf of the guest, within the executable
* mapping of the generated code buffer, then it is a host bug.
*/
if (!in_code_gen_buffer((void *)(pc - tcg_splitwx_diff))) {
die_from_signal(info);
}
if (info->si_code == BUS_ADRALN) {
uintptr_t host_addr = (uintptr_t)info->si_addr;
abi_ptr guest_addr = h2g_nocheck(host_addr);
sigprocmask(SIG_SETMASK, host_signal_mask(uc), NULL);
cpu_loop_exit_sigbus(cpu, guest_addr, access_type, pc);
}
}
static void host_signal_handler(int host_sig, siginfo_t *info, void *puc)
{
CPUState *cpu = thread_cpu;
CPUArchState *env = cpu_env(cpu);
TaskState *ts = cpu->opaque;
target_siginfo_t tinfo;
host_sigcontext *uc = puc;
struct emulated_sigtable *k;
int guest_sig;
uintptr_t pc = 0;
bool sync_sig = false;
void *sigmask;
/*
* Non-spoofed SIGSEGV and SIGBUS are synchronous, and need special
* handling wrt signal blocking and unwinding. Non-spoofed SIGILL,
* SIGFPE, SIGTRAP are always host bugs.
*/
if (info->si_code > 0) {
switch (host_sig) {
case SIGSEGV:
/* Only returns on handle_sigsegv_accerr_write success. */
host_sigsegv_handler(cpu, info, uc);
return;
case SIGBUS:
host_sigbus_handler(cpu, info, uc);
sync_sig = true;
break;
case SIGILL:
case SIGFPE:
case SIGTRAP:
die_from_signal(info);
}
}
/* get target signal number */
guest_sig = host_to_target_signal(host_sig);
if (guest_sig < 1 || guest_sig > TARGET_NSIG) {
return;
}
trace_user_host_signal(env, host_sig, guest_sig);
linux-user: Provide safe_syscall for fixing races between signals and syscalls If a signal is delivered immediately before a blocking system call the handler will only be called after the system call returns, which may be a long time later or never. This is fixed by using a function (safe_syscall) that checks if a guest signal is pending prior to making a system call, and if so does not call the system call and returns -TARGET_ERESTARTSYS. If a signal is received between the check and the system call host_signal_handler() rewinds execution to before the check. This rewinding has the effect of closing the race window so that safe_syscall will reliably either (a) go into the host syscall with no unprocessed guest signals pending or or (b) return -TARGET_ERESTARTSYS so that the caller can deal with the signals. Implementing this requires a per-host-architecture assembly language fragment. This will also resolve the mishandling of the SA_RESTART flag where we would restart a host system call and not call the guest signal handler until the syscall finally completed -- syscall restarting now always happens at the guest syscall level so the guest signal handler will run. (The host syscall will never be restarted because if the host kernel rewinds the PC to point at the syscall insn for a restart then our host_signal_handler() will see this and arrange the guest PC rewind.) This commit contains the infrastructure for implementing safe_syscall and the assembly language fragment for x86-64, but does not change any syscalls to use it. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-14-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: * Avoid having an architecture if-ladder in configure by putting linux-user/host/$(ARCH) on the include path and including safe-syscall.inc.S from it * Avoid ifdef ladder in signal.c by creating new hostdep.h to hold host-architecture-specific things * Added copyright/license header to safe-syscall.inc.S * Rewrote commit message * Added comments to safe-syscall.inc.S * Changed calling convention of safe_syscall() to match syscall() (returns -1 and host error in errno on failure) * Added a long comment in qemu.h about how to use safe_syscall() to implement guest syscalls. ] RV: squashed Peters "fixup! linux-user: compile on non-x86-64 hosts" patch Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2016-05-12 20:47:46 +03:00
host_to_target_siginfo_noswap(&tinfo, info);
k = &ts->sigtab[guest_sig - 1];
k->info = tinfo;
k->pending = guest_sig;
ts->signal_pending = 1;
/*
* For synchronous signals, unwind the cpu state to the faulting
* insn and then exit back to the main loop so that the signal
* is delivered immediately.
*/
if (sync_sig) {
cpu->exception_index = EXCP_INTERRUPT;
cpu_loop_exit_restore(cpu, pc);
}
rewind_if_in_safe_syscall(puc);
/*
* Block host signals until target signal handler entered. We
* can't block SIGSEGV or SIGBUS while we're executing guest
* code in case the guest code provokes one in the window between
* now and it getting out to the main loop. Signals will be
* unblocked again in process_pending_signals().
*
* WARNING: we cannot use sigfillset() here because the sigmask
* field is a kernel sigset_t, which is much smaller than the
* libc sigset_t which sigfillset() operates on. Using sigfillset()
* would write 0xff bytes off the end of the structure and trash
* data on the struct.
*/
sigmask = host_signal_mask(uc);
memset(sigmask, 0xff, SIGSET_T_SIZE);
sigdelset(sigmask, SIGSEGV);
sigdelset(sigmask, SIGBUS);
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
/* interrupt the virtual CPU as soon as possible */
cpu_exit(thread_cpu);
}
/* do_sigaltstack() returns target values and errnos. */
/* compare linux/kernel/signal.c:do_sigaltstack() */
abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr,
CPUArchState *env)
{
target_stack_t oss, *uoss = NULL;
abi_long ret = -TARGET_EFAULT;
if (uoss_addr) {
/* Verify writability now, but do not alter user memory yet. */
if (!lock_user_struct(VERIFY_WRITE, uoss, uoss_addr, 0)) {
goto out;
}
target_save_altstack(&oss, env);
}
if (uss_addr) {
target_stack_t *uss;
if (!lock_user_struct(VERIFY_READ, uss, uss_addr, 1)) {
goto out;
}
ret = target_restore_altstack(uss, env);
if (ret) {
goto out;
avoid TABs in files that only contain a few Most files that have TABs only contain a handful of them. Change them to spaces so that we don't confuse people. disas, standard-headers, linux-headers and libdecnumber are imported from other projects and probably should be exempted from the check. Outside those, after this patch the following files still contain both 8-space and TAB sequences at the beginning of the line. Many of them have a majority of TABs, or were initially committed with all tabs. bsd-user/i386/target_syscall.h bsd-user/x86_64/target_syscall.h crypto/aes.c hw/audio/fmopl.c hw/audio/fmopl.h hw/block/tc58128.c hw/display/cirrus_vga.c hw/display/xenfb.c hw/dma/etraxfs_dma.c hw/intc/sh_intc.c hw/misc/mst_fpga.c hw/net/pcnet.c hw/sh4/sh7750.c hw/timer/m48t59.c hw/timer/sh_timer.c include/crypto/aes.h include/disas/bfd.h include/hw/sh4/sh.h libdecnumber/decNumber.c linux-headers/asm-generic/unistd.h linux-headers/linux/kvm.h linux-user/alpha/target_syscall.h linux-user/arm/nwfpe/double_cpdo.c linux-user/arm/nwfpe/fpa11_cpdt.c linux-user/arm/nwfpe/fpa11_cprt.c linux-user/arm/nwfpe/fpa11.h linux-user/flat.h linux-user/flatload.c linux-user/i386/target_syscall.h linux-user/ppc/target_syscall.h linux-user/sparc/target_syscall.h linux-user/syscall.c linux-user/syscall_defs.h linux-user/x86_64/target_syscall.h slirp/cksum.c slirp/if.c slirp/ip.h slirp/ip_icmp.c slirp/ip_icmp.h slirp/ip_input.c slirp/ip_output.c slirp/mbuf.c slirp/misc.c slirp/sbuf.c slirp/socket.c slirp/socket.h slirp/tcp_input.c slirp/tcpip.h slirp/tcp_output.c slirp/tcp_subr.c slirp/tcp_timer.c slirp/tftp.c slirp/udp.c slirp/udp.h target/cris/cpu.h target/cris/mmu.c target/cris/op_helper.c target/sh4/helper.c target/sh4/op_helper.c target/sh4/translate.c tcg/sparc/tcg-target.inc.c tests/tcg/cris/check_addo.c tests/tcg/cris/check_moveq.c tests/tcg/cris/check_swap.c tests/tcg/multiarch/test-mmap.c ui/vnc-enc-hextile-template.h ui/vnc-enc-zywrle.h util/envlist.c util/readline.c The following have only TABs: bsd-user/i386/target_signal.h bsd-user/sparc64/target_signal.h bsd-user/sparc64/target_syscall.h bsd-user/sparc/target_signal.h bsd-user/sparc/target_syscall.h bsd-user/x86_64/target_signal.h crypto/desrfb.c hw/audio/intel-hda-defs.h hw/core/uboot_image.h hw/sh4/sh7750_regnames.c hw/sh4/sh7750_regs.h include/hw/cris/etraxfs_dma.h linux-user/alpha/termbits.h linux-user/arm/nwfpe/fpopcode.h linux-user/arm/nwfpe/fpsr.h linux-user/arm/syscall_nr.h linux-user/arm/target_signal.h linux-user/cris/target_signal.h linux-user/i386/target_signal.h linux-user/linux_loop.h linux-user/m68k/target_signal.h linux-user/microblaze/target_signal.h linux-user/mips64/target_signal.h linux-user/mips/target_signal.h linux-user/mips/target_syscall.h linux-user/mips/termbits.h linux-user/ppc/target_signal.h linux-user/sh4/target_signal.h linux-user/sh4/termbits.h linux-user/sparc64/target_syscall.h linux-user/sparc/target_signal.h linux-user/x86_64/target_signal.h linux-user/x86_64/termbits.h pc-bios/optionrom/optionrom.h slirp/mbuf.h slirp/misc.h slirp/sbuf.h slirp/tcp.h slirp/tcp_timer.h slirp/tcp_var.h target/i386/svm.h target/sparc/asi.h target/xtensa/core-dc232b/xtensa-modules.inc.c target/xtensa/core-dc233c/xtensa-modules.inc.c target/xtensa/core-de212/core-isa.h target/xtensa/core-de212/xtensa-modules.inc.c target/xtensa/core-fsf/xtensa-modules.inc.c target/xtensa/core-sample_controller/core-isa.h target/xtensa/core-sample_controller/xtensa-modules.inc.c target/xtensa/core-test_kc705_be/core-isa.h target/xtensa/core-test_kc705_be/xtensa-modules.inc.c tests/tcg/cris/check_abs.c tests/tcg/cris/check_addc.c tests/tcg/cris/check_addcm.c tests/tcg/cris/check_addoq.c tests/tcg/cris/check_bound.c tests/tcg/cris/check_ftag.c tests/tcg/cris/check_int64.c tests/tcg/cris/check_lz.c tests/tcg/cris/check_openpf5.c tests/tcg/cris/check_sigalrm.c tests/tcg/cris/crisutils.h tests/tcg/cris/sys.c tests/tcg/i386/test-i386-ssse3.c ui/vgafont.h Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20181213223737.11793-3-pbonzini@redhat.com> Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com> Acked-by: Richard Henderson <richard.henderson@linaro.org> Acked-by: Eric Blake <eblake@redhat.com> Acked-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Stefan Markovic <smarkovic@wavecomp.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-12-14 01:37:37 +03:00
}
}
if (uoss_addr) {
memcpy(uoss, &oss, sizeof(oss));
unlock_user_struct(uoss, uoss_addr, 1);
uoss = NULL;
}
ret = 0;
out:
if (uoss) {
unlock_user_struct(uoss, uoss_addr, 0);
}
return ret;
}
/* do_sigaction() return target values and host errnos */
int do_sigaction(int sig, const struct target_sigaction *act,
struct target_sigaction *oact, abi_ulong ka_restorer)
{
struct target_sigaction *k;
int host_sig;
int ret = 0;
trace_signal_do_sigaction_guest(sig, TARGET_NSIG);
if (sig < 1 || sig > TARGET_NSIG) {
return -TARGET_EINVAL;
}
if (act && (sig == TARGET_SIGKILL || sig == TARGET_SIGSTOP)) {
return -TARGET_EINVAL;
}
if (block_signals()) {
return -QEMU_ERESTARTSYS;
}
k = &sigact_table[sig - 1];
if (oact) {
__put_user(k->_sa_handler, &oact->_sa_handler);
__put_user(k->sa_flags, &oact->sa_flags);
#ifdef TARGET_ARCH_HAS_SA_RESTORER
__put_user(k->sa_restorer, &oact->sa_restorer);
#endif
/* Not swapped. */
oact->sa_mask = k->sa_mask;
}
if (act) {
__get_user(k->_sa_handler, &act->_sa_handler);
__get_user(k->sa_flags, &act->sa_flags);
#ifdef TARGET_ARCH_HAS_SA_RESTORER
__get_user(k->sa_restorer, &act->sa_restorer);
#endif
#ifdef TARGET_ARCH_HAS_KA_RESTORER
k->ka_restorer = ka_restorer;
#endif
/* To be swapped in target_to_host_sigset. */
k->sa_mask = act->sa_mask;
/* we update the host linux signal state */
host_sig = target_to_host_signal(sig);
trace_signal_do_sigaction_host(host_sig, TARGET_NSIG);
if (host_sig > SIGRTMAX) {
/* we don't have enough host signals to map all target signals */
qemu_log_mask(LOG_UNIMP, "Unsupported target signal #%d, ignored\n",
sig);
/*
* we don't return an error here because some programs try to
* register an handler for all possible rt signals even if they
* don't need it.
* An error here can abort them whereas there can be no problem
* to not have the signal available later.
* This is the case for golang,
* See https://github.com/golang/go/issues/33746
* So we silently ignore the error.
*/
return 0;
}
if (host_sig != SIGSEGV && host_sig != SIGBUS) {
struct sigaction act1;
sigfillset(&act1.sa_mask);
act1.sa_flags = SA_SIGINFO;
if (k->_sa_handler == TARGET_SIG_IGN) {
/*
* It is important to update the host kernel signal ignore
* state to avoid getting unexpected interrupted syscalls.
*/
act1.sa_sigaction = (void *)SIG_IGN;
} else if (k->_sa_handler == TARGET_SIG_DFL) {
if (core_dump_signal(sig)) {
act1.sa_sigaction = host_signal_handler;
} else {
act1.sa_sigaction = (void *)SIG_DFL;
}
} else {
act1.sa_sigaction = host_signal_handler;
if (k->sa_flags & TARGET_SA_RESTART) {
act1.sa_flags |= SA_RESTART;
}
}
ret = sigaction(host_sig, &act1, NULL);
}
}
return ret;
}
static void handle_pending_signal(CPUArchState *cpu_env, int sig,
struct emulated_sigtable *k)
{
CPUState *cpu = env_cpu(cpu_env);
abi_ulong handler;
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
sigset_t set;
target_sigset_t target_old_set;
struct target_sigaction *sa;
TaskState *ts = cpu->opaque;
trace_user_handle_signal(cpu_env, sig);
/* dequeue signal */
k->pending = 0;
sig = gdb_handlesig(cpu, sig);
if (!sig) {
sa = NULL;
handler = TARGET_SIG_IGN;
} else {
sa = &sigact_table[sig - 1];
handler = sa->_sa_handler;
}
if (unlikely(qemu_loglevel_mask(LOG_STRACE))) {
print_taken_signal(sig, &k->info);
}
if (handler == TARGET_SIG_DFL) {
/* default handler : ignore some signal. The other are job control or fatal */
if (sig == TARGET_SIGTSTP || sig == TARGET_SIGTTIN || sig == TARGET_SIGTTOU) {
kill(getpid(),SIGSTOP);
} else if (sig != TARGET_SIGCHLD &&
sig != TARGET_SIGURG &&
sig != TARGET_SIGWINCH &&
sig != TARGET_SIGCONT) {
dump_core_and_abort(cpu_env, sig);
}
} else if (handler == TARGET_SIG_IGN) {
/* ignore sig */
} else if (handler == TARGET_SIG_ERR) {
dump_core_and_abort(cpu_env, sig);
} else {
/* compute the blocked signals during the handler execution */
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
sigset_t *blocked_set;
target_to_host_sigset(&set, &sa->sa_mask);
/* SA_NODEFER indicates that the current signal should not be
blocked during the handler */
if (!(sa->sa_flags & TARGET_SA_NODEFER))
sigaddset(&set, target_to_host_signal(sig));
/* save the previous blocked signal state to restore it at the
end of the signal execution (see do_sigreturn) */
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
host_to_target_sigset_internal(&target_old_set, &ts->signal_mask);
/* block signals in the handler */
blocked_set = ts->in_sigsuspend ?
&ts->sigsuspend_mask : &ts->signal_mask;
sigorset(&ts->signal_mask, blocked_set, &set);
ts->in_sigsuspend = 0;
/* if the CPU is in VM86 mode, we restore the 32 bit values */
#if defined(TARGET_I386) && !defined(TARGET_X86_64)
{
CPUX86State *env = cpu_env;
if (env->eflags & VM_MASK)
save_v86_state(env);
}
#endif
/* prepare the stack frame of the virtual CPU */
#if defined(TARGET_ARCH_HAS_SETUP_FRAME)
if (sa->sa_flags & TARGET_SA_SIGINFO) {
setup_rt_frame(sig, sa, &k->info, &target_old_set, cpu_env);
} else {
setup_frame(sig, sa, &target_old_set, cpu_env);
}
#else
/* These targets do not have traditional signals. */
setup_rt_frame(sig, sa, &k->info, &target_old_set, cpu_env);
#endif
if (sa->sa_flags & TARGET_SA_RESETHAND) {
sa->_sa_handler = TARGET_SIG_DFL;
}
}
}
void process_pending_signals(CPUArchState *cpu_env)
{
CPUState *cpu = env_cpu(cpu_env);
int sig;
TaskState *ts = cpu->opaque;
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
sigset_t set;
sigset_t *blocked_set;
while (qatomic_read(&ts->signal_pending)) {
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
sigfillset(&set);
sigprocmask(SIG_SETMASK, &set, 0);
restart_scan:
sig = ts->sync_signal.pending;
if (sig) {
/* Synchronous signals are forced,
* see force_sig_info() and callers in Linux
* Note that not all of our queue_signal() calls in QEMU correspond
* to force_sig_info() calls in Linux (some are send_sig_info()).
* However it seems like a kernel bug to me to allow the process
* to block a synchronous signal since it could then just end up
* looping round and round indefinitely.
*/
if (sigismember(&ts->signal_mask, target_to_host_signal_table[sig])
|| sigact_table[sig - 1]._sa_handler == TARGET_SIG_IGN) {
sigdelset(&ts->signal_mask, target_to_host_signal_table[sig]);
sigact_table[sig - 1]._sa_handler = TARGET_SIG_DFL;
}
handle_pending_signal(cpu_env, sig, &ts->sync_signal);
}
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
for (sig = 1; sig <= TARGET_NSIG; sig++) {
blocked_set = ts->in_sigsuspend ?
&ts->sigsuspend_mask : &ts->signal_mask;
if (ts->sigtab[sig - 1].pending &&
(!sigismember(blocked_set,
target_to_host_signal_table[sig]))) {
handle_pending_signal(cpu_env, sig, &ts->sigtab[sig - 1]);
/* Restart scan from the beginning, as handle_pending_signal
* might have resulted in a new synchronous signal (eg SIGSEGV).
*/
goto restart_scan;
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
}
}
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
/* if no signal is pending, unblock signals and recheck (the act
* of unblocking might cause us to take another host signal which
* will set signal_pending again).
*/
qatomic_set(&ts->signal_pending, 0);
linux-user: Fix race between multiple signals If multiple host signals are received in quick succession they would be queued in TaskState then delivered to the guest in spite of signals being supposed to be blocked by the guest signal handler's sa_mask. Fix this by decoupling the guest signal mask from the host signal mask, so we can have protected sections where all host signals are blocked. In particular we block signals from when host_signal_handler() queues a signal from the guest until process_pending_signals() has unqueued it. We also block signals while we are manipulating the guest signal mask in emulation of sigprocmask and similar syscalls. Blocking host signals also ensures the correct behaviour with respect to multiple threads and the overrun count of timer related signals. Alas blocking and queuing in qemu is still needed because of virtual processor exceptions, SIGSEGV and SIGBUS. Blocking signals inside process_pending_signals() protects against concurrency problems that would otherwise happen if host_signal_handler() ran and accessed the signal data structures while process_pending_signals() was manipulating them. Since we now track the guest signal mask separately from that of the host, the sigsuspend system calls must track the signal mask passed to them, because when we process signals as we leave the sigsuspend the guest signal mask in force is that passed to sigsuspend. Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> Message-id: 1441497448-32489-19-git-send-email-T.E.Baldwin99@members.leeds.ac.uk [PMM: make signal_pending a simple flag rather than a word with two flag bits; ensure we don't call block_signals() twice in sigreturn codepaths; document and assert() the guarantee that using do_sigprocmask() to get the current mask never fails; use the qemu atomics.h functions rather than raw volatile variable access; add extra commentary and documentation; block SIGSEGV/SIGBUS in block_signals() and in process_pending_signals() because they can't occur synchronously here; check the right do_sigprocmask() call for errors in ssetmask syscall; expand commit message; fixed sigsuspend() hanging] Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
2016-05-27 17:51:49 +03:00
ts->in_sigsuspend = 0;
set = ts->signal_mask;
sigdelset(&set, SIGSEGV);
sigdelset(&set, SIGBUS);
sigprocmask(SIG_SETMASK, &set, 0);
}
ts->in_sigsuspend = 0;
}
int process_sigsuspend_mask(sigset_t **pset, target_ulong sigset,
target_ulong sigsize)
{
TaskState *ts = (TaskState *)thread_cpu->opaque;
sigset_t *host_set = &ts->sigsuspend_mask;
target_sigset_t *target_sigset;
if (sigsize != sizeof(*target_sigset)) {
/* Like the kernel, we enforce correct size sigsets */
return -TARGET_EINVAL;
}
target_sigset = lock_user(VERIFY_READ, sigset, sigsize, 1);
if (!target_sigset) {
return -TARGET_EFAULT;
}
target_to_host_sigset(host_set, target_sigset);
unlock_user(target_sigset, sigset, 0);
*pset = host_set;
return 0;
}