mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-29 00:01:12 +00:00
d40ac01cbb
The recursive lock used on abort does not synchronize with a new process
creation (either by fork-like interfaces or posix_spawn ones), nor it
is reinitialized after fork().
Also, the SIGABRT unblock before raise() shows another race condition,
where a fork or posix_spawn() call by another thread, just after the
recursive lock release and before the SIGABRT signal, might create
programs with a non-expected signal mask. With the default option
(without POSIX_SPAWN_SETSIGDEF), the process can see SIG_DFL for
SIGABRT, where it should be SIG_IGN.
To fix the AS-safe, raise() does not change the process signal mask,
and an AS-safe lock is used if a SIGABRT is installed or the process
is blocked or ignored. With the signal mask change removal,
there is no need to use a recursive loc. The lock is also taken on
both _Fork() and posix_spawn(), to avoid the spawn process to see the
abort handler as SIG_DFL.
A read-write lock is used to avoid serialize _Fork and posix_spawn
execution. Both sigaction (SIGABRT) and abort() requires to lock
as writer (since both change the disposition).
The fallback is also simplified: there is no need to use a loop of
ABORT_INSTRUCTION after _exit() (if the syscall does not terminate the
process, the system is broken).
The proposed fix changes how setjmp works on a SIGABRT handler, where
glibc does not save the signal mask. So usage like the below will now
always abort.
static volatile int chk_fail_ok;
static jmp_buf chk_fail_buf;
static void
handler (int sig)
{
if (chk_fail_ok)
{
chk_fail_ok = 0;
longjmp (chk_fail_buf, 1);
}
else
_exit (127);
}
[...]
signal (SIGABRT, handler);
[....]
chk_fail_ok = 1;
if (! setjmp (chk_fail_buf))
{
// Something that can calls abort, like a failed fortify function.
chk_fail_ok = 0;
printf ("FAIL\n");
}
Such cases will need to use sigsetjmp instead.
The _dl_start_profile calls sigaction through _profil, and to avoid
pulling abort() on loader the call is replaced with __libc_sigaction.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>
128 lines
3.5 KiB
C
128 lines
3.5 KiB
C
/* Low-level statistical profiling support function. Mostly POSIX.1 version.
|
|
Copyright (C) 1996-2024 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include <sys/types.h>
|
|
#include <unistd.h>
|
|
#include <errno.h>
|
|
#include <signal.h>
|
|
#include <sys/time.h>
|
|
#include <stdint.h>
|
|
#include <libc-internal.h>
|
|
#include <sigsetops.h>
|
|
|
|
#ifndef SIGPROF
|
|
|
|
#include <gmon/profil.c>
|
|
|
|
#else
|
|
|
|
static u_short *samples;
|
|
static size_t nsamples;
|
|
static size_t pc_offset;
|
|
static u_int pc_scale;
|
|
|
|
static inline void
|
|
profil_count (uintptr_t pc)
|
|
{
|
|
size_t i = (pc - pc_offset) / 2;
|
|
|
|
if (sizeof (unsigned long long int) > sizeof (size_t))
|
|
i = (unsigned long long int) i * pc_scale / 65536;
|
|
else
|
|
i = i / 65536 * pc_scale + i % 65536 * pc_scale / 65536;
|
|
|
|
if (i < nsamples)
|
|
++samples[i];
|
|
}
|
|
|
|
/* Get the machine-dependent definition of `__profil_counter', the signal
|
|
handler for SIGPROF. It calls `profil_count' (above) with the PC of the
|
|
interrupted code. */
|
|
#include "profil-counter.h"
|
|
|
|
/* Enable statistical profiling, writing samples of the PC into at most
|
|
SIZE bytes of SAMPLE_BUFFER; every processor clock tick while profiling
|
|
is enabled, the system examines the user PC and increments
|
|
SAMPLE_BUFFER[((PC - OFFSET) / 2) * SCALE / 65536]. If SCALE is zero,
|
|
disable profiling. Returns zero on success, -1 on error. */
|
|
|
|
int
|
|
__profil (u_short *sample_buffer, size_t size, size_t offset, u_int scale)
|
|
{
|
|
struct sigaction act;
|
|
struct itimerval timer;
|
|
#if !IS_IN (rtld)
|
|
static struct sigaction oact;
|
|
static struct itimerval otimer;
|
|
# define oact_ptr &oact
|
|
# define otimer_ptr &otimer
|
|
|
|
if (sample_buffer == NULL)
|
|
{
|
|
/* Disable profiling. */
|
|
if (samples == NULL)
|
|
/* Wasn't turned on. */
|
|
return 0;
|
|
|
|
if (__setitimer (ITIMER_PROF, &otimer, NULL) < 0)
|
|
return -1;
|
|
samples = NULL;
|
|
return __libc_sigaction (SIGPROF, &oact, NULL);
|
|
}
|
|
|
|
if (samples)
|
|
{
|
|
/* Was already turned on. Restore old timer and signal handler
|
|
first. */
|
|
if (__setitimer (ITIMER_PROF, &otimer, NULL) < 0
|
|
|| __libc_sigaction (SIGPROF, &oact, NULL) < 0)
|
|
return -1;
|
|
}
|
|
#else
|
|
/* In ld.so profiling should never be disabled once it runs. */
|
|
//assert (sample_buffer != NULL);
|
|
# define oact_ptr NULL
|
|
# define otimer_ptr NULL
|
|
#endif
|
|
|
|
samples = sample_buffer;
|
|
nsamples = size / sizeof *samples;
|
|
pc_offset = offset;
|
|
pc_scale = scale;
|
|
|
|
#ifdef SA_SIGINFO
|
|
act.sa_sigaction = __profil_counter;
|
|
act.sa_flags = SA_SIGINFO;
|
|
#else
|
|
act.sa_handler = __profil_counter;
|
|
act.sa_flags = 0;
|
|
#endif
|
|
act.sa_flags |= SA_RESTART;
|
|
__sigfillset (&act.sa_mask);
|
|
if (__libc_sigaction (SIGPROF, &act, oact_ptr) < 0)
|
|
return -1;
|
|
|
|
timer.it_value.tv_sec = 0;
|
|
timer.it_value.tv_usec = 1000000 / __profile_frequency ();
|
|
timer.it_interval = timer.it_value;
|
|
return __setitimer (ITIMER_PROF, &timer, otimer_ptr);
|
|
}
|
|
weak_alias (__profil, profil)
|
|
|
|
#endif
|