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sparc: Move sigreturn stub to assembly
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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@ -11,8 +11,12 @@ ifeq ($(subdir),sysvipc)
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sysdep_routines += getshmlba
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endif
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ifeq ($(subdir),signal)
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sysdep_routines += sigreturn_stub
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endif
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ifeq ($(subdir),nptl)
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# pull in __syscall_error routine
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libpthread-routines += sysdep
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libpthread-shared-only-routines += sysdep
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libpthread-routines += sysdep sigreturn_stub
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libpthread-shared-only-routines += sysdep sigreturn_stub
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endif
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@ -24,8 +24,8 @@
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#include <kernel_sigaction.h>
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#include <sysdep.h>
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static void __rt_sigreturn_stub (void);
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static void __sigreturn_stub (void);
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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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@ -35,25 +35,3 @@ static void __sigreturn_stub (void);
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(sigsetsize)
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#include <sysdeps/unix/sysv/linux/sigaction.c>
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static
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inhibit_stack_protector
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void
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__rt_sigreturn_stub (void)
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{
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__asm__ ("mov %0, %%g1\n\t"
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"ta 0x10\n\t"
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: /* no outputs */
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: "i" (__NR_rt_sigreturn));
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}
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static
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inhibit_stack_protector
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void
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__sigreturn_stub (void)
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{
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__asm__ ("mov %0, %%g1\n\t"
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"ta 0x10\n\t"
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: /* no outputs */
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: "i" (__NR_sigreturn));
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}
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34
sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S
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34
sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S
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@ -0,0 +1,34 @@
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/* Sigreturn stub function used on sa_restore field.
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Copyright (C) 2020 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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#include <sysdep.h>
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/* These functions must not change the register window or the stack
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pointer [1].
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[1] https://lkml.org/lkml/2016/5/27/465 */
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ENTRY (__rt_sigreturn_stub)
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mov __NR_rt_sigreturn, %g1
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ta 0x10
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END (__rt_sigreturn_stub)
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ENTRY (__sigreturn_stub)
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mov __NR_sigreturn, %g1
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ta 0x10
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END (__sigreturn_stub)
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@ -22,21 +22,11 @@
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#include <syscall.h>
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#include <sysdep.h>
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static void __rt_sigreturn_stub (void);
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/* Defined on sigreturn_stub.S. */
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void __rt_sigreturn_stub (void);
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#define STUB(act, sigsetsize) \
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(((unsigned long) &__rt_sigreturn_stub) - 8), \
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(sigsetsize)
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#include <sysdeps/unix/sysv/linux/sigaction.c>
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static
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inhibit_stack_protector
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void
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__rt_sigreturn_stub (void)
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{
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__asm__ ("mov %0, %%g1\n\t"
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"ta 0x6d\n\t"
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: /* no outputs */
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: "i" (__NR_rt_sigreturn));
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}
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29
sysdeps/unix/sysv/linux/sparc/sparc64/sigreturn_stub.S
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29
sysdeps/unix/sysv/linux/sparc/sparc64/sigreturn_stub.S
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@ -0,0 +1,29 @@
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/* Sigreturn stub function used on sa_restore field.
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Copyright (C) 2020 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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#include <sysdep.h>
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/* This function must not change the register window or the stack
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pointer [1].
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[1] https://lkml.org/lkml/2016/5/27/465 */
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ENTRY (__rt_sigreturn_stub)
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mov __NR_rt_sigreturn, %g1
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ta 0x6d
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END (__rt_sigreturn_stub)
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