[src/trunk]: src/sys Register KTR events for debugger related signals

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

details:   https://anonhg.NetBSD.org/src/rev/671fc9173871
branches:  trunk
changeset: 456323:671fc9173871
user:      kamil <kamil%NetBSD.org@localhost>
date:      Fri May 03 22:34:21 2019 +0000

description:
Register KTR events for debugger related signals

Register signals for:

 - crashes (FPE, SEGV, FPE, ILL, BUS)
 - LWP events
 - CHLD (FORK/VFORK/VFORK_DONE) events -- temporarily disabled
 - EXEC events

While there refactor related functions in order to simplify the code.

Add missing comment documentation for recently added kernel functions.

diffstat:

 sys/kern/kern_exec.c |   8 +--
 sys/kern/kern_fork.c |  29 +++++++++------
 sys/kern/kern_lwp.c  |   8 +--
 sys/kern/kern_sig.c  |  91 +++++++++++++++++++++++++++++++++++++++------------
 sys/kern/sys_lwp.c   |   8 +--
 sys/sys/signalvar.h  |   4 +-
 6 files changed, 97 insertions(+), 51 deletions(-)

diffs (truncated from 414 to 300 lines):

diff -r f8185a867f59 -r 671fc9173871 sys/kern/kern_exec.c
--- a/sys/kern/kern_exec.c      Fri May 03 19:06:50 2019 +0000
+++ b/sys/kern/kern_exec.c      Fri May 03 22:34:21 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_exec.c,v 1.463 2019/05/01 17:21:55 kamil Exp $    */
+/*     $NetBSD: kern_exec.c,v 1.464 2019/05/03 22:34:21 kamil Exp $    */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -59,7 +59,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_exec.c,v 1.463 2019/05/01 17:21:55 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_exec.c,v 1.464 2019/05/03 22:34:21 kamil Exp $");
 
 #include "opt_exec.h"
 #include "opt_execfmt.h"
@@ -1271,9 +1271,7 @@
 
        if ((p->p_slflag & (PSL_TRACED|PSL_SYSCALL)) == PSL_TRACED) {
                mutex_enter(p->p_lock);
-               eventswitch(SIGTRAP, TRAP_EXEC);
-               // XXX ktrpoint(KTR_PSIG)
-               mutex_exit(p->p_lock);
+               eventswitch(TRAP_EXEC);
                mutex_enter(proc_lock);
        }
 
diff -r f8185a867f59 -r 671fc9173871 sys/kern/kern_fork.c
--- a/sys/kern/kern_fork.c      Fri May 03 19:06:50 2019 +0000
+++ b/sys/kern/kern_fork.c      Fri May 03 22:34:21 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_fork.c,v 1.211 2019/05/01 18:01:54 kamil Exp $    */
+/*     $NetBSD: kern_fork.c,v 1.212 2019/05/03 22:34:21 kamil Exp $    */
 
 /*-
  * Copyright (c) 1999, 2001, 2004, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.211 2019/05/01 18:01:54 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.212 2019/05/03 22:34:21 kamil Exp $");
 
 #include "opt_ktrace.h"
 #include "opt_dtrace.h"
@@ -203,6 +203,9 @@
  */
 static struct timeval fork_tfmrate = { 10, 0 };
 
+/*
+ * Check if a process is traced and shall inform about FORK events.
+ */
 static inline bool
 tracefork(struct proc *p, int flags)
 {
@@ -211,6 +214,9 @@
            (PSL_TRACEFORK|PSL_TRACED) && (flags & FORK_PPWAIT) == 0;
 }
 
+/*
+ * Check if a process is traced and shall inform about VFORK events.
+ */
 static inline bool
 tracevfork(struct proc *p, int flags)
 {
@@ -219,6 +225,9 @@
            (PSL_TRACEVFORK|PSL_TRACED) && (flags & FORK_PPWAIT) != 0;
 }
 
+/*
+ * Check if a process is traced and shall inform about VFORK_DONE events.
+ */
 static inline bool
 tracevforkdone(struct proc *p, int flags)
 {
@@ -595,9 +604,7 @@
         */
        if (tracefork(p1, flags) || tracevfork(p1, flags)) {
                mutex_enter(p1->p_lock);
-               eventswitch(SIGTRAP, TRAP_CHLD);
-               // XXX ktrpoint(KTR_PSIG)
-               mutex_exit(p1->p_lock);
+               eventswitch(TRAP_CHLD);
                mutex_enter(proc_lock);
        }
 
@@ -614,16 +621,16 @@
        if (tracevforkdone(p1, flags)) {
                mutex_enter(p1->p_lock);
                p1->p_vfpid_done = retval[0];
-               eventswitch(SIGTRAP, TRAP_CHLD);
-               // XXX ktrpoint(KTR_PSIG)
-               mutex_exit(p1->p_lock);
-               // proc_lock unlocked
+               eventswitch(TRAP_CHLD);
        } else
                mutex_exit(proc_lock);
 
        return 0;
 }
 
+/*
+ * MI code executed in each newly spawned process before returning to userland.
+ */
 void
 child_return(void *arg)
 {
@@ -639,9 +646,7 @@
                }
 
                mutex_enter(p->p_lock);
-               eventswitch(SIGTRAP, TRAP_CHLD);
-               // XXX ktrpoint(KTR_PSIG)
-               mutex_exit(p->p_lock);
+               eventswitch(TRAP_CHLD);
        }
 
 my_tracer_is_gone:
diff -r f8185a867f59 -r 671fc9173871 sys/kern/kern_lwp.c
--- a/sys/kern/kern_lwp.c       Fri May 03 19:06:50 2019 +0000
+++ b/sys/kern/kern_lwp.c       Fri May 03 22:34:21 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_lwp.c,v 1.199 2019/05/02 22:23:49 kamil Exp $     */
+/*     $NetBSD: kern_lwp.c,v 1.200 2019/05/03 22:34:21 kamil Exp $     */
 
 /*-
  * Copyright (c) 2001, 2006, 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -211,7 +211,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_lwp.c,v 1.199 2019/05/02 22:23:49 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_lwp.c,v 1.200 2019/05/03 22:34:21 kamil Exp $");
 
 #include "opt_ddb.h"
 #include "opt_lockdebug.h"
@@ -1083,9 +1083,7 @@
            (PSL_TRACED|PSL_TRACELWP_EXIT)) {
                mutex_enter(p->p_lock);
                p->p_lwp_exited = l->l_lid;
-               eventswitch(SIGTRAP, TRAP_LWP);
-               // XXX ktrpoint(KTR_PSIG)
-               mutex_exit(p->p_lock);
+               eventswitch(TRAP_LWP);
                mutex_enter(proc_lock);
        }
 
diff -r f8185a867f59 -r 671fc9173871 sys/kern/kern_sig.c
--- a/sys/kern/kern_sig.c       Fri May 03 19:06:50 2019 +0000
+++ b/sys/kern/kern_sig.c       Fri May 03 22:34:21 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_sig.c,v 1.356 2019/05/02 22:23:49 kamil Exp $     */
+/*     $NetBSD: kern_sig.c,v 1.357 2019/05/03 22:34:21 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 1.356 2019/05/02 22:23:49 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_sig.c,v 1.357 2019/05/03 22:34:21 kamil Exp $");
 
 #include "opt_ptrace.h"
 #include "opt_dtrace.h"
@@ -902,6 +902,7 @@
        struct sigacts  *ps;
        int signo = ksi->ksi_signo;
        sigset_t *mask;
+       sig_t action;
 
        KASSERT(KSI_TRAP_P(ksi));
 
@@ -912,6 +913,10 @@
        mutex_enter(proc_lock);
        mutex_enter(p->p_lock);
 
+       mask = &l->l_sigmask;
+       ps = p->p_sigacts;
+       action = SIGACTION_PS(ps, signo).sa_handler;
+
        if (ISSET(p->p_slflag, PSL_TRACED) &&
            !(p->p_pptr == p->p_opptr && ISSET(p->p_lflag, PL_PPWAIT)) &&
            p->p_xsig != SIGKILL &&
@@ -921,14 +926,16 @@
                p->p_sigctx.ps_lwp = ksi->ksi_lid;
                p->p_sigctx.ps_info = ksi->ksi_info;
                sigswitch(0, signo, false);
-               // XXX ktrpoint(KTR_PSIG)
-               mutex_exit(p->p_lock);
+
+               if (ktrpoint(KTR_PSIG)) {
+                       if (p->p_emul->e_ktrpsig)
+                               p->p_emul->e_ktrpsig(signo, action, mask, ksi);
+                       else
+                               ktrpsig(signo, action, mask, ksi);
+               }
                return;
        }
 
-       mask = &l->l_sigmask;
-       ps = p->p_sigacts;
-
        const bool caught = sigismember(&p->p_sigctx.ps_sigcatch, signo);
        const bool masked = sigismember(mask, signo);
        if (caught && !masked) {
@@ -936,15 +943,12 @@
                l->l_ru.ru_nsignals++;
                kpsendsig(l, ksi, mask);
                mutex_exit(p->p_lock);
+
                if (ktrpoint(KTR_PSIG)) {
                        if (p->p_emul->e_ktrpsig)
-                               p->p_emul->e_ktrpsig(signo,
-                                   SIGACTION_PS(ps, signo).sa_handler,
-                                   mask, ksi);
+                               p->p_emul->e_ktrpsig(signo, action, mask, ksi);
                        else
-                               ktrpsig(signo, 
-                                   SIGACTION_PS(ps, signo).sa_handler,
-                                   mask, ksi);
+                               ktrpsig(signo, action, mask, ksi);
                }
                return;
        }
@@ -954,7 +958,7 @@
         * reset it to the default action so that the process or
         * its tracer will be notified.
         */
-       const bool ignored = SIGACTION_PS(ps, signo).sa_handler == SIG_IGN;
+       const bool ignored = action == SIG_IGN;
        if (masked || ignored) {
                mutex_enter(&ps->sa_mutex);
                sigdelset(mask, signo); 
@@ -1539,35 +1543,68 @@
        }
 }
 
+/*
+ * Stop the current process and switch away to the debugger notifying
+ * an event specific to a traced process only.
+ */
 void
-eventswitch(int signo, int code)
+eventswitch(int code)
 {
        struct lwp *l = curlwp;
        struct proc *p = l->l_proc;
+       struct sigacts *ps;
+       sigset_t *mask;
+       sig_t action;
+       ksiginfo_t ksi;
+       const int signo = SIGTRAP;
 
        KASSERT(mutex_owned(proc_lock));
        KASSERT(mutex_owned(p->p_lock));
+       KASSERT(p->p_pptr != initproc);
        KASSERT(l->l_stat == LSONPROC);
-       KASSERT((l->l_flag & LW_SYSTEM) == 0);
+       KASSERT(ISSET(p->p_slflag, PSL_TRACED));
+       KASSERT(!ISSET(l->l_flag, LW_SYSTEM));
        KASSERT(p->p_nrlwps > 0);
+       KASSERT((code == TRAP_CHLD) || (code == TRAP_LWP) ||
+               (code == TRAP_EXEC));
 
        /*
         * If there's a pending SIGKILL process it immediately.
         */
        if (p->p_xsig == SIGKILL ||
            sigismember(&p->p_sigpend.sp_set, SIGKILL)) {
+               mutex_exit(p->p_lock);
                mutex_exit(proc_lock);
                return;
        }
 
+       KSI_INIT_TRAP(&ksi);
+       ksi.ksi_lid = l->l_lid;
+       ksi.ksi_info._signo = signo;
+       ksi.ksi_info._code = code;
+
+       /* Needed for ktrace */
+       ps = p->p_sigacts;
+       action = SIGACTION_PS(ps, signo).sa_handler;
+       mask = &l->l_sigmask;
+
        p->p_xsig = signo;
        p->p_sigctx.ps_faked = true;
-       p->p_sigctx.ps_lwp = l->l_lid;
-       memset(&p->p_sigctx.ps_info, 0, sizeof(p->p_sigctx.ps_info));
-       p->p_sigctx.ps_info._signo = signo;
-       p->p_sigctx.ps_info._code = code;
+       p->p_sigctx.ps_lwp = ksi.ksi_lid;
+       p->p_sigctx.ps_info = ksi.ksi_info;
 
        sigswitch(0, signo, false);
+
+       /* XXX: hangs for VFORK */
+       if (code == TRAP_CHLD)