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Add some more futex gunk and explain why it does not work (yet). 

Now skype aborts with a futex timeout, instead of a stack smash leading
to a SEGV.
This commit is contained in:
christos 2013-04-16 23:03:05 +00:00
parent 86479a1389
commit 3d6e1ab522
2 changed files with 81 additions and 52 deletions
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127
sys/compat/linux/common/linux_futex.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: linux_futex.c,v 1.28 2011/11/18 04:07:44 christos Exp $ */
/* $NetBSD: linux_futex.c,v 1.29 2013/04/16 23:03:05 christos Exp $ */
/*-
* Copyright (c) 2005 Emmanuel Dreyfus, all rights reserved.
@ -32,7 +32,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(1, "$NetBSD: linux_futex.c,v 1.28 2011/11/18 04:07:44 christos Exp $");
__KERNEL_RCSID(1, "$NetBSD: linux_futex.c,v 1.29 2013/04/16 23:03:05 christos Exp $");
#include <sys/param.h>
#include <sys/time.h>
@ -67,6 +67,7 @@ struct waiting_proc {
struct futex {
void *f_uaddr;
int f_refcount;
uint32_t f_bitset;
LIST_ENTRY(futex) f_list;
TAILQ_HEAD(, waiting_proc) f_waiting_proc;
TAILQ_HEAD(, waiting_proc) f_requeue_proc;
@ -105,7 +106,7 @@ linux_futex_fini(void)
static struct waiting_proc *futex_wp_alloc(void);
static void futex_wp_free(struct waiting_proc *);
static struct futex *futex_get(void *);
static struct futex *futex_get(void *, uint32_t);
static void futex_ref(struct futex *);
static void futex_put(struct futex *);
static int futex_sleep(struct futex **, lwp_t *, int, struct waiting_proc *);
@ -127,7 +128,7 @@ linux_sys_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_
struct timespec ts = { 0, 0 };
int error;
if ((SCARG(uap, op) & ~LINUX_FUTEX_PRIVATE_FLAG) == LINUX_FUTEX_WAIT &&
if ((SCARG(uap, op) & LINUX_FUTEX_CMD_MASK) == LINUX_FUTEX_WAIT &&
SCARG(uap, timeout) != NULL) {
if ((error = copyin(SCARG(uap, timeout),
&lts, sizeof(lts))) != 0) {
@ -149,15 +150,31 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
syscallarg(int *) uaddr2;
syscallarg(int) val3;
} */
int val;
int val, val3;
int ret;
int error = 0;
struct futex *f;
struct futex *newf;
int timeout_hz;
int tout;
struct futex *f2;
struct waiting_proc *wp;
int op_ret;
int op_ret, cmd;
clockid_t clk;
cmd = SCARG(uap, op) & LINUX_FUTEX_CMD_MASK;
val3 = SCARG(uap, val3);
if (SCARG(uap, op) & LINUX_FUTEX_CLOCK_REALTIME) {
switch (cmd) {
case LINUX_FUTEX_WAIT_BITSET:
case LINUX_FUTEX_WAIT:
clk = CLOCK_REALTIME;
break;
default:
return ENOSYS;
}
} else
clk = CLOCK_MONOTONIC;
/*
* Our implementation provides only private futexes. Most of the apps
@ -165,11 +182,33 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
* all futexes as private by clearing the FUTEX_PRIVATE_FLAG. It works
* in most cases (ie. when futexes are not shared on file descriptor
* or between different processes).
*
* Note that we don't handle bitsets at all at the moment. We need
* to move from refcounting uaddr's to handling multiple futex entries
* pointing to the same uaddr, but having possibly different bitmask.
* Perhaps move to an implementation where each uaddr has a list of
* futexes.
*/
switch (SCARG(uap, op) & ~LINUX_FUTEX_PRIVATE_FLAG) {
switch (cmd) {
case LINUX_FUTEX_WAIT:
val3 = FUTEX_BITSET_MATCH_ANY;
/*FALLTHROUGH*/
case LINUX_FUTEX_WAIT_BITSET:
if ((error = ts2timo(clk, 0, ts, &tout, NULL)) != 0) {
/*
* If the user process requests a non null timeout,
* make sure we do not turn it into an infinite
* timeout because tout is 0.
*
* We use a minimal timeout of 1/hz. Maybe it would make
* sense to just return ETIMEDOUT without sleeping.
*/
if (error == ETIMEDOUT && SCARG(uap, timeout) != NULL)
tout = 1;
else
return error;
}
FUTEX_SYSTEM_LOCK;
if ((error = copyin(SCARG(uap, uaddr),
&val, sizeof(val))) != 0) {
FUTEX_SYSTEM_UNLOCK;
@ -187,27 +226,11 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
SCARG(uap, uaddr), val, (long long)ts->tv_sec,
ts->tv_nsec));
if ((error = itimespecfix(ts)) != 0) {
FUTEX_SYSTEM_UNLOCK;
return error;
}
timeout_hz = tstohz(ts);
/*
* If the user process requests a non null timeout,
* make sure we do not turn it into an infinite
* timeout because timeout_hz is 0.
*
* We use a minimal timeout of 1/hz. Maybe it would make
* sense to just return ETIMEDOUT without sleeping.
*/
if (SCARG(uap, timeout) != NULL && timeout_hz == 0)
timeout_hz = 1;
wp = futex_wp_alloc();
FUTEX_LOCK;
f = futex_get(SCARG(uap, uaddr));
ret = futex_sleep(&f, l, timeout_hz, wp);
f = futex_get(SCARG(uap, uaddr), val3);
ret = futex_sleep(&f, l, tout, wp);
futex_put(f);
FUTEX_UNLOCK;
futex_wp_free(wp);
@ -238,6 +261,9 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
break;
case LINUX_FUTEX_WAKE:
val = FUTEX_BITSET_MATCH_ANY;
/*FALLTHROUGH*/
case LINUX_FUTEX_WAKE_BITSET:
/*
* XXX: Linux is able cope with different addresses
* corresponding to the same mapped memory in the sleeping
@ -249,7 +275,7 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
FUTEX_SYSTEM_LOCK;
FUTEX_LOCK;
f = futex_get(SCARG(uap, uaddr));
f = futex_get(SCARG(uap, uaddr), val3);
*retval = futex_wake(f, SCARG(uap, val), NULL, 0);
futex_put(f);
FUTEX_UNLOCK;
@ -266,7 +292,7 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
return error;
}
if (val != SCARG(uap, val3)) {
if (val != val3) {
FUTEX_SYSTEM_UNLOCK;
return EAGAIN;
}
@ -278,8 +304,8 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
(int)(unsigned long)SCARG(uap, timeout)));
FUTEX_LOCK;
f = futex_get(SCARG(uap, uaddr));
newf = futex_get(SCARG(uap, uaddr2));
f = futex_get(SCARG(uap, uaddr), val3);
newf = futex_get(SCARG(uap, uaddr2), val3);
*retval = futex_wake(f, SCARG(uap, val), newf,
(int)(unsigned long)SCARG(uap, timeout));
futex_put(f);
@ -299,8 +325,8 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
(int)(unsigned long)SCARG(uap, timeout)));
FUTEX_LOCK;
f = futex_get(SCARG(uap, uaddr));
newf = futex_get(SCARG(uap, uaddr2));
f = futex_get(SCARG(uap, uaddr), val3);
newf = futex_get(SCARG(uap, uaddr2), val3);
*retval = futex_wake(f, SCARG(uap, val), newf,
(int)(unsigned long)SCARG(uap, timeout));
futex_put(f);
@ -311,8 +337,7 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
break;
case LINUX_FUTEX_FD:
FUTEXPRINTF(("linux_sys_futex: unimplemented op %d\n",
SCARG(uap, op)));
FUTEXPRINTF(("%s: unimplemented op %d\n", __func__, cmd));
return ENOSYS;
case LINUX_FUTEX_WAKE_OP:
FUTEX_SYSTEM_LOCK;
@ -320,20 +345,20 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
FUTEXPRINTF(("FUTEX_WAKE_OP %d.%d: uaddr = %p, op = %d, "
"val = %d, uaddr2 = %p, val2 = %d\n",
l->l_proc->p_pid, l->l_lid,
SCARG(uap, uaddr), SCARG(uap, op), SCARG(uap, val),
SCARG(uap, uaddr), cmd, SCARG(uap, val),
SCARG(uap, uaddr2),
(int)(unsigned long)SCARG(uap, timeout)));
FUTEX_LOCK;
f = futex_get(SCARG(uap, uaddr));
f2 = futex_get(SCARG(uap, uaddr2));
f = futex_get(SCARG(uap, uaddr), val3);
f2 = futex_get(SCARG(uap, uaddr2), val3);
FUTEX_UNLOCK;
/*
* This function returns positive number as results and
* negative as errors
*/
op_ret = futex_atomic_op(l, SCARG(uap, val3), SCARG(uap, uaddr2));
op_ret = futex_atomic_op(l, val3, SCARG(uap, uaddr2));
FUTEX_LOCK;
if (op_ret < 0) {
futex_put(f);
@ -361,8 +386,7 @@ linux_do_futex(struct lwp *l, const struct linux_sys_futex_args *uap, register_t
*retval = ret;
break;
default:
FUTEXPRINTF(("linux_sys_futex: unknown op %d\n",
SCARG(uap, op)));
FUTEXPRINTF(("%s: unknown op %d\n", __func__, cmd));
return ENOSYS;
}
return 0;
@ -387,7 +411,7 @@ futex_wp_free(struct waiting_proc *wp)
}
static struct futex *
futex_get(void *uaddr)
futex_get(void *uaddr, uint32_t bitset)
{
struct futex *f;
@ -403,6 +427,7 @@ futex_get(void *uaddr)
/* Not found, create it */
f = kmem_zalloc(sizeof(*f), KM_SLEEP);
f->f_uaddr = uaddr;
f->f_bitset = bitset;
f->f_refcount = 1;
TAILQ_INIT(&f->f_waiting_proc);
TAILQ_INIT(&f->f_requeue_proc);
@ -483,8 +508,8 @@ futex_wake(struct futex *f, int n, struct futex *newf, int n2)
TAILQ_FOREACH(wp, &f->f_waiting_proc, wp_list) {
KASSERT(wp->wp_new_futex == NULL);
FUTEXPRINTF(("futex_wake: signal f %p l %p ref %d\n",
f, wp->wp_l, f->f_refcount));
FUTEXPRINTF(("%s: signal f %p l %p ref %d\n", __func__,
f, wp->wp_l, f->f_refcount));
cv_signal(&wp->wp_futex_cv);
if (count <= n) {
count++;
@ -496,8 +521,8 @@ futex_wake(struct futex *f, int n, struct futex *newf, int n2)
futex_ref(newf);
wp->wp_new_futex = newf;
TAILQ_INSERT_TAIL(&newf->f_requeue_proc, wp, wp_rqlist);
FUTEXPRINTF(("futex_wake: requeue newf %p l %p ref %d\n",
newf, wp->wp_l, newf->f_refcount));
FUTEXPRINTF(("%s: requeue newf %p l %p ref %d\n",
__func__, newf, wp->wp_l, newf->f_refcount));
if (count - n >= n2)
goto out;
}
@ -515,8 +540,8 @@ futex_wake(struct futex *f, int n, struct futex *newf, int n2)
TAILQ_FOREACH_SAFE(wp, &f->f_requeue_proc, wp_rqlist, wpnext) {
KASSERT(wp->wp_new_futex == f);
FUTEXPRINTF(("futex_wake: unrequeue f %p l %p ref %d\n",
f, wp->wp_l, f->f_refcount));
FUTEXPRINTF(("%s: unrequeue f %p l %p ref %d\n", __func__,
f, wp->wp_l, f->f_refcount));
wp->wp_new_futex = NULL;
TAILQ_REMOVE(&f->f_requeue_proc, wp, wp_rqlist);
futex_put(f);
@ -531,8 +556,8 @@ futex_wake(struct futex *f, int n, struct futex *newf, int n2)
futex_ref(newf);
wp->wp_new_futex = newf;
TAILQ_INSERT_TAIL(&newf->f_requeue_proc, wp, wp_rqlist);
FUTEXPRINTF(("futex_wake: rerequeue newf %p l %p ref %d\n",
newf, wp->wp_l, newf->f_refcount));
FUTEXPRINTF(("%s: rerequeue newf %p l %p ref %d\n",
__func__, newf, wp->wp_l, newf->f_refcount));
if (count - n >= n2)
break;
}
@ -701,7 +726,7 @@ retry:
if (!pi && (uval & FUTEX_WAITERS)) {
FUTEX_LOCK;
f = futex_get(uaddr);
f = futex_get(uaddr, FUTEX_BITSET_MATCH_ANY);
futex_wake(f, 1, NULL, 0);
FUTEX_UNLOCK;
}

6
sys/compat/linux/common/linux_futex.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: linux_futex.h,v 1.6 2013/01/11 02:49:09 christos Exp $ */
/* $NetBSD: linux_futex.h,v 1.7 2013/04/16 23:03:05 christos Exp $ */
/*-
* Copyright (c) 2005 Emmanuel Dreyfus, all rights reserved.
@ -50,6 +50,8 @@
#define LINUX_FUTEX_PRIVATE_FLAG 128
#define LINUX_FUTEX_CLOCK_REALTIME 256
#define LINUX_FUTEX_CMD_MASK \
(~(LINUX_FUTEX_PRIVATE_FLAG|LINUX_FUTEX_CLOCK_REALTIME))
#define FUTEX_OP_SET 0
#define FUTEX_OP_ADD 1
@ -79,6 +81,8 @@ struct linux_robust_list_head {
#define FUTEX_OWNER_DIED 0x40000000
#define FUTEX_TID_MASK 0x3fffffff
#define FUTEX_BITSET_MATCH_ANY 0xffffffff
void release_futexes(struct lwp *);
struct linux_sys_futex_args;
int linux_do_futex(struct lwp *, const struct linux_sys_futex_args *,