[src/trunk]: src/sys/kern Stop resetting signal context on a trap signal unde...

[kamil <kamil%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/4d444c11ba1d
branches:  trunk
changeset: 997462:4d444c11ba1d
user:      kamil <kamil%NetBSD.org@localhost>
date:      Fri Mar 08 23:32:30 2019 +0000

description:
Stop resetting signal context on a trap signal under a debugger

In case of a crash signal, notify debugger immediately passing the signal
regardless of signal masking/ignoring.

While there pass signals emitted by a debugger to debuggee. Debugger calls
proc_unstop() that sets p_stat to SACTIVE and this signal wasn't passed
to tracee.

This scenario appeared to be triggered in recently added crash signal ATF
ptrace(2) tests.

diffstat:

 sys/kern/kern_sig.c |  24 +++++++++++++++++++-----
 1 files changed, 19 insertions(+), 5 deletions(-)

diffs (57 lines):

diff -r 103ec9eda2ad -r 4d444c11ba1d sys/kern/kern_sig.c
--- a/sys/kern/kern_sig.c       Fri Mar 08 23:10:52 2019 +0000
+++ b/sys/kern/kern_sig.c       Fri Mar 08 23:32:30 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_sig.c,v 1.350 2018/11/29 10:27:36 maxv Exp $      */
+/*     $NetBSD: kern_sig.c,v 1.351 2019/03/08 23:32:30 kamil Exp $     */
 
 /*-
  * Copyright (c) 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -70,7 +70,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_sig.c,v 1.350 2018/11/29 10:27:36 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_sig.c,v 1.351 2019/03/08 23:32:30 kamil Exp $");
 
 #include "opt_ptrace.h"
 #include "opt_dtrace.h"
@@ -911,13 +911,25 @@
        KASSERT(!cpu_intr_p());
        mutex_enter(proc_lock);
        mutex_enter(p->p_lock);
+
+       if (ISSET(p->p_slflag, PSL_TRACED) &&
+           !(p->p_pptr == p->p_opptr && ISSET(p->p_lflag, PL_PPWAIT))) {
+               p->p_xsig = signo;
+               p->p_sigctx.ps_faked = true; // XXX
+               p->p_sigctx.ps_info._signo = signo;
+               p->p_sigctx.ps_info._code = ksi->ksi_code;
+               sigswitch(0, signo, false);
+               // XXX ktrpoint(KTR_PSIG)
+               mutex_exit(p->p_lock);
+               return;
+       }
+
        mask = &l->l_sigmask;
        ps = p->p_sigacts;
 
-       const bool traced = (p->p_slflag & PSL_TRACED) != 0;
        const bool caught = sigismember(&p->p_sigctx.ps_sigcatch, signo);
        const bool masked = sigismember(mask, signo);
-       if (!traced && caught && !masked) {
+       if (caught && !masked) {
                mutex_exit(proc_lock);
                l->l_ru.ru_nsignals++;
                kpsendsig(l, ksi, mask);
@@ -1678,7 +1690,9 @@
                if (p->p_stat == SSTOP || (p->p_sflag & PS_STOPPING) != 0) {
                        sigswitch(PS_NOCLDSTOP, 0, true);
                        signo = sigchecktrace();
-               } else
+               } else if (p->p_stat == SACTIVE)
+                       signo = sigchecktrace();
+               else
                        signo = 0;
 
                /* Signals from the debugger are "out of band". */