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b33e946fbb
It seems that some gcc versions might generates a stack frame for the
sigreturn stub requires on sparc signal handling. For instance:
$ cat test.c
#define _GNU_SOURCE
#include <sys/syscall.h>
__attribute__ ((__optimize__ ("-fno-stack-protector")))
void
__sigreturn_stub (void)
{
__asm__ ("mov %0, %%g1\n\t"
"ta 0x10\n\t"
: /* no outputs */
: "i" (SYS_rt_sigreturn));
}
$ gcc -v
[...]
gcc version 9.2.1 20200224 (Debian 9.2.1-30)
$ gcc -O2 -m64 test.c -S -o -
[...]
__sigreturn_stub:
save %sp, -176, %sp
#APP
! 9 "t.c" 1
mov 101, %g1
ta 0x10
! 0 "" 2
#NO_APP
.size __sigreturn_stub, .-__sigreturn_stub
As indicated by kernel developers [1], the sigreturn stub can not change
the register window or the stack pointer since the kernel has setup the
restore frame at a precise location relative to the stack pointer when
the stub is invoked.
I tried to play with some compiler flags and even with _Noreturn and
__builtin_unreachable after the asm does not help (and Sparc does not
support naked functions).
To avoid similar issues, as the stack-protector support also have
stumbled, this patch moves the implementation of the sigreturn stubs to
assembly.
Checked on sparcv9-linux-gnu and sparc64-linux-gnu with gcc 9.2.1
and gcc 7.5.0.
[1] https://lkml.org/lkml/2016/5/27/465
38 lines
1.3 KiB
C
38 lines
1.3 KiB
C
/* POSIX.1 sigaction call for Linux/SPARC.
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Copyright (C) 1997-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Miguel de Icaza <miguel@nuclecu.unam.mx>, 1997.
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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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#include <string.h>
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#include <syscall.h>
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#include <sys/signal.h>
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#include <errno.h>
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#include <kernel_sigaction.h>
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#include <sysdep.h>
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void __rt_sigreturn_stub (void);
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void __sigreturn_stub (void);
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#define STUB(act, sigsetsize) \
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(act) ? ((unsigned long)((act->sa_flags & SA_SIGINFO) \
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? &__rt_sigreturn_stub \
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: &__sigreturn_stub) - 8) \
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: 0, \
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(sigsetsize)
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#include <sysdeps/unix/sysv/linux/sigaction.c>
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