Introduce new ptrace(2) operations: PT_SET_SIGPASS and PT_GET_SIGPASS
They deliver the logic of bypassing selected signals directly to the debuggee, without informing the debugger. This can be used to implement the QPassSignals GDB/LLDB protocol. This call can be useful to avoid signal races in ATF ptrace tests.
This commit is contained in:
kamil
parent
2c2a96663a
commit
48b46ced17
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@ -1,7 +1,7 @@
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.\" $NetBSD: ptrace.2,v 1.83 2020/01/04 04:40:17 kamil Exp $
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.\" $NetBSD: ptrace.2,v 1.84 2020/05/14 13:32:15 kamil Exp $
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.\"
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.\" This file is in the public domain.
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.Dd January 4, 2019
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.Dd May 14, 2020
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.Dt PTRACE 2
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.Os
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.Sh NAME
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@ -623,6 +623,31 @@ The
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.Fa data
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argument should be set to
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.Li sizeof(struct ptrace_siginfo) .
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.It Dv PT_SET_SIGPASS
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This request can be used to specify mask of signals that should be passed
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directly to the debuggee, without reporting to the tracer.
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A pointer to sigset_t is passed in
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.Fa addr .
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The
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.Fa data
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argument should be set to
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.Li sizeof(sigset_t) .
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.Pp
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It is not permitted to mask SIGSTOP and SIGKILL.
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All debugger related signals
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(SIGTRAP, SIGILL, SIGSEGV, SIGBUS, SIGFPE)
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are reported to the tracer without interruption,
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unless they were emitted by a non-crash source.
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.It Dv PT_GET_SIGPASS
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This request can be used to determine mask of signals passed directly to the debuggee.
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A pointer to sigset_t is passed in
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.Fa addr .
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The
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.Fa data
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argument should be set to
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.Li sizeof(sigset_t) .
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.Pp
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Upon debugger attach the sigpass mask shall be empty.
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.It Dv PT_RESUME
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Allow execution of a specified thread,
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change its state from suspended to continued.
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@ -1,4 +1,4 @@
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/* $NetBSD: kern_sig.c,v 1.388 2020/05/07 20:02:34 kamil Exp $ */
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/* $NetBSD: kern_sig.c,v 1.389 2020/05/14 13:32:15 kamil Exp $ */
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/*-
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* Copyright (c) 2006, 2007, 2008, 2019 The NetBSD Foundation, Inc.
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@ -70,7 +70,7 @@
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: kern_sig.c,v 1.388 2020/05/07 20:02:34 kamil Exp $");
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__KERNEL_RCSID(0, "$NetBSD: kern_sig.c,v 1.389 2020/05/14 13:32:15 kamil Exp $");
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#include "opt_ptrace.h"
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#include "opt_dtrace.h"
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@ -1302,6 +1302,7 @@ kpsignal2(struct proc *p, ksiginfo_t *ksi)
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lwpid_t lid;
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sig_t action;
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bool toall;
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bool traced;
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int error = 0;
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KASSERT(!cpu_intr_p());
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@ -1329,11 +1330,13 @@ kpsignal2(struct proc *p, ksiginfo_t *ksi)
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prop = sigprop[signo];
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toall = ((prop & SA_TOALL) != 0);
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lid = toall ? 0 : ksi->ksi_lid;
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traced = ISSET(p->p_slflag, PSL_TRACED) &&
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!sigismember(&p->p_sigctx.ps_sigpass, signo);
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/*
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* If proc is traced, always give parent a chance.
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*/
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if (p->p_slflag & PSL_TRACED) {
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if (traced) {
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action = SIG_DFL;
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if (lid == 0) {
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@ -1428,7 +1431,7 @@ kpsignal2(struct proc *p, ksiginfo_t *ksi)
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* or for an SA process.
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*/
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if (p->p_stat == SACTIVE && (p->p_sflag & PS_STOPPING) == 0) {
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if ((p->p_slflag & PSL_TRACED) != 0)
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if (traced)
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goto deliver;
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/*
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@ -1444,7 +1447,7 @@ kpsignal2(struct proc *p, ksiginfo_t *ksi)
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* - If traced, then no action is needed, unless killing.
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* - Run the process only if sending SIGCONT or SIGKILL.
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*/
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if ((p->p_slflag & PSL_TRACED) != 0 && signo != SIGKILL) {
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if (traced && signo != SIGKILL) {
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goto out;
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}
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if ((prop & SA_CONT) != 0 || signo == SIGKILL) {
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@ -1456,7 +1459,7 @@ kpsignal2(struct proc *p, ksiginfo_t *ksi)
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p->p_pptr->p_nstopchild--;
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p->p_stat = SACTIVE;
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p->p_sflag &= ~PS_STOPPING;
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if (p->p_slflag & PSL_TRACED) {
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if (traced) {
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KASSERT(signo == SIGKILL);
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goto deliver;
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}
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@ -1487,7 +1490,7 @@ kpsignal2(struct proc *p, ksiginfo_t *ksi)
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/*
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* Make signal pending.
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*/
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KASSERT((p->p_slflag & PSL_TRACED) == 0);
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KASSERT(!traced);
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if ((error = sigput(&p->p_sigpend, p, kp)) != 0)
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goto out;
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deliver:
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@ -1844,6 +1847,7 @@ issignal(struct lwp *l)
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int siglwp, signo, prop;
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sigpend_t *sp;
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sigset_t ss;
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bool traced;
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p = l->l_proc;
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sp = NULL;
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@ -1910,6 +1914,9 @@ issignal(struct lwp *l)
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}
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}
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traced = ISSET(p->p_slflag, PSL_TRACED) &&
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!sigismember(&p->p_sigctx.ps_sigpass, signo);
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if (sp) {
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/* Overwrite process' signal context to correspond
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* to the currently reported LWP. This is necessary
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@ -1937,7 +1944,7 @@ issignal(struct lwp *l)
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* we are being traced.
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*/
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if (sigismember(&p->p_sigctx.ps_sigignore, signo) &&
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(p->p_slflag & PSL_TRACED) == 0) {
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!traced) {
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/* Discard the signal. */
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continue;
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}
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@ -1947,7 +1954,7 @@ issignal(struct lwp *l)
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* by the debugger. If the our parent is our debugger waiting
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* for us and we vforked, don't hang as we could deadlock.
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*/
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if (ISSET(p->p_slflag, PSL_TRACED) && signo != SIGKILL &&
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if (traced && signo != SIGKILL &&
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!(ISSET(p->p_lflag, PL_PPWAIT) &&
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(p->p_pptr == p->p_opptr))) {
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/*
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@ -2004,7 +2011,7 @@ issignal(struct lwp *l)
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* XXX Don't hold proc_lock for p_lflag,
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* but it's not a big deal.
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*/
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if ((ISSET(p->p_slflag, PSL_TRACED) &&
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if ((traced &&
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!(ISSET(p->p_lflag, PL_PPWAIT) &&
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(p->p_pptr == p->p_opptr))) ||
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((p->p_lflag & PL_ORPHANPG) != 0 &&
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@ -2035,8 +2042,7 @@ issignal(struct lwp *l)
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* to take action on an ignored signal other
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* than SIGCONT, unless process is traced.
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*/
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if ((prop & SA_CONT) == 0 &&
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(p->p_slflag & PSL_TRACED) == 0)
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if ((prop & SA_CONT) == 0 && !traced)
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printf_nolog("issignal\n");
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#endif
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continue;
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@ -1,4 +1,4 @@
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/* $NetBSD: sys_ptrace_common.c,v 1.79 2020/05/08 10:35:51 kamil Exp $ */
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/* $NetBSD: sys_ptrace_common.c,v 1.80 2020/05/14 13:32:15 kamil Exp $ */
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/*-
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* Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
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@ -118,7 +118,7 @@
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: sys_ptrace_common.c,v 1.79 2020/05/08 10:35:51 kamil Exp $");
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__KERNEL_RCSID(0, "$NetBSD: sys_ptrace_common.c,v 1.80 2020/05/14 13:32:15 kamil Exp $");
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#ifdef _KERNEL_OPT
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#include "opt_ptrace.h"
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@ -290,6 +290,8 @@ ptrace_listener_cb(kauth_cred_t cred, kauth_action_t action, void *cookie,
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case PT_STOP:
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case PT_LWPSTATUS:
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case PT_LWPNEXT:
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case PT_SET_SIGPASS:
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case PT_GET_SIGPASS:
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result = KAUTH_RESULT_ALLOW;
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break;
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@ -500,6 +502,8 @@ ptrace_allowed(struct lwp *l, int req, struct proc *t, struct proc *p,
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case PT_STOP:
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case PT_LWPSTATUS:
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case PT_LWPNEXT:
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case PT_SET_SIGPASS:
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case PT_GET_SIGPASS:
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/*
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* You can't do what you want to the process if:
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* (1) It's not being traced at all,
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@ -621,6 +625,47 @@ ptrace_set_siginfo(struct proc *t, struct lwp **lt, struct ptrace_methods *ptm,
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return 0;
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}
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static int
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ptrace_get_sigpass(struct proc *t, void *addr, size_t data)
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{
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sigset_t set;
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if (data > sizeof(set) || data <= 0) {
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DPRINTF(("%s: invalid data: %zu < %zu <= 0\n",
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__func__, sizeof(set), data));
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return EINVAL;
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}
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set = t->p_sigctx.ps_sigpass;
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return copyout(&set, addr, data);
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}
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static int
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ptrace_set_sigpass(struct proc *t, void *addr, size_t data)
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{
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sigset_t set;
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int error;
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if (data > sizeof(set) || data <= 0) {
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DPRINTF(("%s: invalid data: %zu < %zu <= 0\n",
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__func__, sizeof(set), data));
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return EINVAL;
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}
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memset(&set, 0, sizeof(set));
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if ((error = copyin(addr, &set, data)))
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return error;
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/* We catch SIGSTOP and cannot intercept SIGKILL. */
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sigminusset(&sigcantmask, &set);
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t->p_sigctx.ps_sigpass = set;
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return 0;
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}
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static int
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ptrace_get_event_mask(struct proc *t, void *addr, size_t data)
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{
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@ -1395,6 +1440,9 @@ do_ptrace(struct ptrace_methods *ptm, struct lwp *l, int req, pid_t pid,
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CLR(t->p_slflag,
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PSL_TRACED|PSL_TRACEDCHILD|PSL_SYSCALL);
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/* clear sigpass mask */
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sigemptyset(&t->p_sigctx.ps_sigpass);
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/* give process back to original parent or init */
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if (t->p_opptr != t->p_pptr) {
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struct proc *pp = t->p_opptr;
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@ -1499,6 +1547,14 @@ do_ptrace(struct ptrace_methods *ptm, struct lwp *l, int req, pid_t pid,
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error = ptrace_lwpstatus(t, ptm, <, addr, data, true);
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break;
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case PT_SET_SIGPASS:
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error = ptrace_set_sigpass(t, addr, data);
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break;
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case PT_GET_SIGPASS:
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error = ptrace_get_sigpass(t, addr, data);
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break;
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#ifdef PT_REGISTERS
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case_PT_SETREGS
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case_PT_GETREGS
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@ -1,4 +1,4 @@
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/* $NetBSD: ptrace.h,v 1.69 2019/12/26 08:52:38 kamil Exp $ */
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/* $NetBSD: ptrace.h,v 1.70 2020/05/14 13:32:15 kamil Exp $ */
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/*-
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* Copyright (c) 1984, 1993
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@ -63,6 +63,8 @@
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#define PT_STOP 23 /* stop the child process */
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#define PT_LWPSTATUS 24 /* get info about the LWP */
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#define PT_LWPNEXT 25 /* get info about next LWP */
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#define PT_SET_SIGPASS 26 /* set signals to pass to debuggee */
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#define PT_GET_SIGPASS 27 /* get signals to pass to debuggee */
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#define PT_FIRSTMACH 32 /* for machine-specific requests */
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#include <machine/ptrace.h> /* machine-specific requests, if any */
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@ -93,7 +95,9 @@
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/* 22 */ "PT_SUSPEND", \
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/* 23 */ "PT_STOP", \
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/* 24 */ "PT_LWPSTATUS", \
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/* 25 */ "PT_LWPNEXT"
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/* 25 */ "PT_LWPNEXT", \
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/* 26 */ "PT_SET_SIGPASS", \
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/* 27 */ "PT_GET_SIGPASS"
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/* PT_{G,S}EVENT_MASK */
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typedef struct ptrace_event {
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@ -1,4 +1,4 @@
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/* $NetBSD: signalvar.h,v 1.101 2020/04/05 20:53:17 christos Exp $ */
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/* $NetBSD: signalvar.h,v 1.102 2020/05/14 13:32:15 kamil Exp $ */
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/*
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* Copyright (c) 1991, 1993
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@ -85,6 +85,7 @@ struct sigctx {
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void *ps_sigcode; /* address of signal trampoline */
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sigset_t ps_sigignore; /* Signals being ignored. */
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sigset_t ps_sigcatch; /* Signals being caught by user. */
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sigset_t ps_sigpass; /* Signals evading the debugger. */
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};
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/* additional signal action values, used only temporarily/internally */
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