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

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

details:   https://anonhg.NetBSD.org/src/rev/14ff6c694905
branches:  trunk
changeset: 972055:14ff6c694905
user:      kamil <kamil%NetBSD.org@localhost>
date:      Thu May 14 19:21:35 2020 +0000

description:
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.

Fixes PR lib/55241 by Andreas Gustafsson

diffstat:

 tests/lib/libc/sys/t_ptrace_fork_wait.h |  26 +++++++++++++++-----------
 1 files changed, 15 insertions(+), 11 deletions(-)

diffs (54 lines):

diff -r 5cc2f8f877da -r 14ff6c694905 tests/lib/libc/sys/t_ptrace_fork_wait.h
--- a/tests/lib/libc/sys/t_ptrace_fork_wait.h   Thu May 14 19:21:06 2020 +0000
+++ b/tests/lib/libc/sys/t_ptrace_fork_wait.h   Thu May 14 19:21:35 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: t_ptrace_fork_wait.h,v 1.2 2020/05/11 20:58:48 kamil Exp $     */
+/*     $NetBSD: t_ptrace_fork_wait.h,v 1.3 2020/05/14 19:21:35 kamil Exp $     */
 
 /*-
  * Copyright (c) 2016, 2017, 2018, 2020 The NetBSD Foundation, Inc.
@@ -38,6 +38,7 @@
 #if defined(TWAIT_HAVE_STATUS)
        int status;
 #endif
+       sigset_t set;
        ptrace_state_t state;
        const int slen = sizeof(state);
        ptrace_event_t event;
@@ -98,6 +99,19 @@
                event.pe_set_event |= PTRACE_VFORK_DONE;
        SYSCALL_REQUIRE(ptrace(PT_SET_EVENT_MASK, child, &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, child, &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, child, (void *)1, 0) != -1);
@@ -207,16 +221,6 @@
        }
 #endif
 
-       DPRINTF("Before calling %s() for the child - expected stopped "
-           "SIGCHLD\n", TWAIT_FNAME);
-       TWAIT_REQUIRE_SUCCESS(wpid = TWAIT_GENERIC(child, &status, 0), child);
-
-       validate_status_stopped(status, SIGCHLD);
-
-       DPRINTF("Before resuming the child process where it left off and "
-           "without signal to be sent\n");
-       SYSCALL_REQUIRE(ptrace(PT_CONTINUE, child, (void *)1, 0) != -1);
-
        DPRINTF("Before calling %s() for the child - expected exited\n",
            TWAIT_FNAME);
        TWAIT_REQUIRE_SUCCESS(wpid = TWAIT_GENERIC(child, &status, 0), child);