[src/trunk]: src/tests/lib/libc/sys Ignore interception of SIGCHLD signals in...

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

details:   https://anonhg.NetBSD.org/src/rev/977c98995084
branches:  trunk
changeset: 932817:977c98995084
user:      kamil <kamil%NetBSD.org@localhost>
date:      Sat May 16 23:10:26 2020 +0000

description:
Ignore interception of SIGCHLD signals in the debugger

Set SIGPASS for SIGCHLD for the traced child in the following tests:
 - unrelated_tracer_fork*
 - unrelated_tracer_vfork*
 - unrelated_tracer_posix_spawn*

There is a race that SIGCHLD might be blocked during forking and dropped.

PR/55241 by Andreas Gustafsson

diffstat:

 tests/lib/libc/sys/t_ptrace_fork_wait.h |  28 +++++++++++++++++-----------
 1 files changed, 17 insertions(+), 11 deletions(-)

diffs (56 lines):

diff -r 5c96104f524c -r 977c98995084 tests/lib/libc/sys/t_ptrace_fork_wait.h
--- a/tests/lib/libc/sys/t_ptrace_fork_wait.h   Sat May 16 23:06:40 2020 +0000
+++ b/tests/lib/libc/sys/t_ptrace_fork_wait.h   Sat May 16 23:10:26 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: t_ptrace_fork_wait.h,v 1.5 2020/05/16 22:07:06 kamil Exp $     */
+/*     $NetBSD: t_ptrace_fork_wait.h,v 1.6 2020/05/16 23:10:26 kamil Exp $     */
 
 /*-
  * Copyright (c) 2016, 2017, 2018, 2020 The NetBSD Foundation, Inc.
@@ -337,6 +337,7 @@
        int status;
 #endif
 
+       sigset_t set;
        struct ptrace_siginfo info;
        ptrace_state_t state;
        const int slen = sizeof(state);
@@ -453,6 +454,21 @@
                SYSCALL_REQUIRE(ptrace(PT_SET_EVENT_MASK, tracee, &event, elen)
                    != -1);
 
+               /*
+                * Ignore interception of the SIGCHLD signals.
+                *
+                * SIGCHLD once blocked is discarded by the kernel as it has the
+                * SA_IGNORE property. During the fork(2) operation all signals
+                * can be shortly blocked and missed (unless there is a
+                * registered signal handler in the traced child). This leads to
+                * a race in this test if there would be an intention to catch
+                * SIGCHLD.
+                */
+               sigemptyset(&set);
+               sigaddset(&set, SIGCHLD);
+               SYSCALL_REQUIRE(ptrace(PT_SET_SIGPASS, tracee, &set,
+                   sizeof(set)) != -1);
+
                DPRINTF("Before resuming the child process where it left off "
                    "and without signal to be sent\n");
                SYSCALL_REQUIRE(ptrace(PT_CONTINUE, tracee, (void *)1, 0) != -1);
@@ -559,16 +575,6 @@
                            wpid = TWAIT_GENERIC(tracee2, &status, 0));
                }
 
-               DPRINTF("Before calling %s() for the tracee - expected stopped "
-                   "SIGCHLD\n", TWAIT_FNAME);
-               TWAIT_REQUIRE_SUCCESS(wpid = TWAIT_GENERIC(tracee, &status, 0), tracee);
-
-               validate_status_stopped(status, SIGCHLD);
-
-               DPRINTF("Before resuming the tracee process where it left off and "
-                   "without signal to be sent\n");
-               SYSCALL_REQUIRE(ptrace(PT_CONTINUE, tracee, (void *)1, 0) != -1);
-
                DPRINTF("Before calling %s() for the tracee - expected exited\n",
                    TWAIT_FNAME);
                TWAIT_REQUIRE_SUCCESS(wpid = TWAIT_GENERIC(tracee, &status, 0), tracee);