From b33e946fbb1659d2c5937c4dd756a7c49a132dff Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Thu, 5 Mar 2020 13:38:24 -0300 Subject: 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 __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 --- sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c | 14 ++--------- .../unix/sysv/linux/sparc/sparc64/sigreturn_stub.S | 29 ++++++++++++++++++++++ 2 files changed, 31 insertions(+), 12 deletions(-) create mode 100644 sysdeps/unix/sysv/linux/sparc/sparc64/sigreturn_stub.S (limited to 'sysdeps/unix/sysv/linux/sparc/sparc64') diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c b/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c index 9c0dc2a630..4e26172321 100644 --- a/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c +++ b/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c @@ -22,21 +22,11 @@ #include #include -static void __rt_sigreturn_stub (void); +/* Defined on sigreturn_stub.S. */ +void __rt_sigreturn_stub (void); #define STUB(act, sigsetsize) \ (((unsigned long) &__rt_sigreturn_stub) - 8), \ (sigsetsize) #include - -static -inhibit_stack_protector -void -__rt_sigreturn_stub (void) -{ - __asm__ ("mov %0, %%g1\n\t" - "ta 0x6d\n\t" - : /* no outputs */ - : "i" (__NR_rt_sigreturn)); -} diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/sigreturn_stub.S b/sysdeps/unix/sysv/linux/sparc/sparc64/sigreturn_stub.S new file mode 100644 index 0000000000..add4766831 --- /dev/null +++ b/sysdeps/unix/sysv/linux/sparc/sparc64/sigreturn_stub.S @@ -0,0 +1,29 @@ +/* Sigreturn stub function used on sa_restore field. + Copyright (C) 2020 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 + . */ + +#include + +/* This function must not change the register window or the stack + pointer [1]. + + [1] https://lkml.org/lkml/2016/5/27/465 */ + +ENTRY (__rt_sigreturn_stub) + mov __NR_rt_sigreturn, %g1 + ta 0x6d +END (__rt_sigreturn_stub) -- cgit 1.4.1