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1b132d55e2
The posix_spawn on sparc issues invalid sigprocmask calls:
rt_sigprocmask(0xffe5e15c /* SIG_??? */, ~[], 0xffe5e1dc, 8) = -1 EINVAL (Invalid argument)
Which make support/tst-support_capture_subprocess fails with random
output (due the child signal being wrongly captured by the parent).
Tracking the culprit it seems to be a wrong code generation in the
INTERNAL_SYSCALL due the automatic sigset_t used on
__libc_signal_block_all:
return INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_BLOCK, &SIGALL_SET,
set, _NSIG / 8);
Where SIGALL_SET is defined as:
((__sigset_t) { .__val = {[0 ... _SIGSET_NWORDS-1 ] = -1 } })
Building the expanded __libc_signal_block_all on sparc64 with recent
compiler (gcc 8.3.1 and 9.1.1):
#include <signal>
int
_libc_signal_block_all (sigset_t *set)
{
INTERNAL_SYSCALL_DECL (err);
return INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_BLOCK, &SIGALL_SET,
set, _NSIG / 8);
}
The first argument (SIG_BLOCK) is not correctly set on 'o0' register:
__libc_signal_block_all:
save %sp, -304, %sp
add %fp, 1919, %o0
mov 128, %o2
sethi %hi(.LC0), %o1
call memcpy, 0
or %o1, %lo(.LC0), %o1
add %fp, 1919, %o1
mov %i0, %o2
mov 8, %o3
mov 103, %g1
ta 0x6d;
bcc,pt %xcc, 1f
mov 0, %g1
sub %g0, %o0, %o0
mov 1, %g1
1: sra %o0, 0, %i0
return %i7+8
nop
Where if SIGALL_SET is defined a const object, gcc correctly sets the
expected kernel argument in correct register:
sethi %hi(.LC0), %o1
call memcpy, 0
or %o1, %lo(.LC0), %o1
-> mov 1, %o0
add %fp, 1919, %o1
Another possible fix is use a static const object. Although there
should not be a difference between a const compound literal and a static
const object, the gcc C99 status page [1] has a note stating that this
optimization is not implemented:
"const-qualified compound literals could share storage with each
other and with string literals, but currently don't.".
This patch fixes it by moving both sigset_t that represent the
signal sets to static const data object. It generates slight better
code where the object reference is used directly instead of a stack
allocation plus the content materialization.
Checked on x86_64-linux-gnu, i686-linux-gnu, and sparc64-linux-gnu.
[1] https://gcc.gnu.org/c99status.html
94 lines
2.7 KiB
C
94 lines
2.7 KiB
C
/* Special use of signals internally. Linux version.
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Copyright (C) 2014-2019 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef __INTERNAL_SIGNALS_H
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# define __INTERNAL_SIGNALS_H
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#include <signal.h>
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#include <sigsetops.h>
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#include <stdbool.h>
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#include <limits.h>
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#include <sysdep.h>
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/* The signal used for asynchronous cancelation. */
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#define SIGCANCEL __SIGRTMIN
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/* Signal needed for the kernel-supported POSIX timer implementation.
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We can reuse the cancellation signal since we can distinguish
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cancellation from timer expirations. */
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#define SIGTIMER SIGCANCEL
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/* Signal used to implement the setuid et.al. functions. */
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#define SIGSETXID (__SIGRTMIN + 1)
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/* Return is sig is used internally. */
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static inline bool
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__is_internal_signal (int sig)
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{
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return (sig == SIGCANCEL) || (sig == SIGSETXID);
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}
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/* Remove internal glibc signal from the mask. */
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static inline void
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__clear_internal_signals (sigset_t *set)
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{
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__sigdelset (set, SIGCANCEL);
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__sigdelset (set, SIGSETXID);
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}
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static const sigset_t sigall_set = {
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.__val = {[0 ... _SIGSET_NWORDS-1 ] = -1 }
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};
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/* Block all signals, including internal glibc ones. */
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static inline int
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__libc_signal_block_all (sigset_t *set)
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{
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INTERNAL_SYSCALL_DECL (err);
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return INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_BLOCK, &sigall_set,
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set, _NSIG / 8);
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}
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/* Block all application signals (excluding internal glibc ones). */
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static inline int
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__libc_signal_block_app (sigset_t *set)
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{
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sigset_t allset = sigall_set;
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__clear_internal_signals (&allset);
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INTERNAL_SYSCALL_DECL (err);
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return INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_BLOCK, &allset,
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set, _NSIG / 8);
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}
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/* Restore current process signal mask. */
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static inline int
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__libc_signal_restore_set (const sigset_t *set)
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{
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INTERNAL_SYSCALL_DECL (err);
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return INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_SETMASK, set, NULL,
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_NSIG / 8);
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}
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/* Used to communicate with signal handler. */
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extern struct xid_command *__xidcmd attribute_hidden;
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#endif
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