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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
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| .. | ||
| bits | ||
| fpu | ||
| sparcv9/fpu | ||
| ____longjmp_chk.S | ||
| alphasort64.c | ||
| arch-syscall.h | ||
| brk.c | ||
| c++-types.data | ||
| clone.S | ||
| fxstat.c | ||
| fxstatat.c | ||
| getcontext.S | ||
| Implies | ||
| jmp_buf-macros.h | ||
| kernel_stat.h | ||
| ld.abilist | ||
| libanl.abilist | ||
| libBrokenLocale.abilist | ||
| libc.abilist | ||
| libcrypt.abilist | ||
| libdl.abilist | ||
| libm.abilist | ||
| libnsl.abilist | ||
| libpthread.abilist | ||
| libresolv.abilist | ||
| librt.abilist | ||
| libthread_db.abilist | ||
| libutil.abilist | ||
| localplt.data | ||
| lxstat.c | ||
| makecontext.c | ||
| Makefile | ||
| nldbl-abi.h | ||
| pipe.S | ||
| register-dump.h | ||
| setcontext.S | ||
| shlib-versions | ||
| sigaction.c | ||
| sigcontextinfo.h | ||
| sigreturn_stub.S | ||
| swapcontext.S | ||
| syscall.S | ||
| syscalls.list | ||
| sysdep.h | ||
| ucontext_i.sym | ||
| Versions | ||
| versionsort64.c | ||
| vfork.S | ||
| xstat.c | ||