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From: Tulio Magno Quites Machado Filho <tuliom@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc/ibm/2.30/master] sparc: Move sigreturn stub to assembly Date: Tue, 12 May 2020 18:43:18 +0000 (GMT) [thread overview] Message-ID: <20200512184318.59E4C386F02B@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b3778c01b74fe4d42fad9841576ecca0c1698556 commit b3778c01b74fe4d42fad9841576ecca0c1698556 Author: Adhemerval Zanella <adhemerval.zanella@linaro.org> Date: Thu Mar 5 13:38:24 2020 -0300 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 (cherry picked from commit b33e946fbb1659d2c5937c4dd756a7c49a132dff) Diff: --- sysdeps/unix/sysv/linux/sparc/Makefile | 8 +++-- sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c | 26 ++--------------- .../unix/sysv/linux/sparc/sparc32/sigreturn_stub.S | 34 ++++++++++++++++++++++ sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c | 14 ++------- .../unix/sysv/linux/sparc/sparc64/sigreturn_stub.S | 29 ++++++++++++++++++ 5 files changed, 73 insertions(+), 38 deletions(-) diff --git a/sysdeps/unix/sysv/linux/sparc/Makefile b/sysdeps/unix/sysv/linux/sparc/Makefile index fb3ee5b8a1..7b91ff1824 100644 --- a/sysdeps/unix/sysv/linux/sparc/Makefile +++ b/sysdeps/unix/sysv/linux/sparc/Makefile @@ -15,8 +15,12 @@ ifeq ($(subdir),sysvipc) sysdep_routines += getshmlba endif +ifeq ($(subdir),signal) +sysdep_routines += sigreturn_stub +endif + ifeq ($(subdir),nptl) # pull in __syscall_error routine -libpthread-routines += sysdep -libpthread-shared-only-routines += sysdep +libpthread-routines += sysdep sigreturn_stub +libpthread-shared-only-routines += sysdep sigreturn_stub endif diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c b/sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c index de7ef6f151..f36e924af4 100644 --- a/sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c +++ b/sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c @@ -24,8 +24,8 @@ #include <kernel_sigaction.h> #include <sysdep.h> -static void __rt_sigreturn_stub (void); -static void __sigreturn_stub (void); +void __rt_sigreturn_stub (void); +void __sigreturn_stub (void); #define STUB(act, sigsetsize) \ (act) ? ((unsigned long)((act->sa_flags & SA_SIGINFO) \ @@ -35,25 +35,3 @@ static void __sigreturn_stub (void); (sigsetsize) #include <sysdeps/unix/sysv/linux/sigaction.c> - -static -inhibit_stack_protector -void -__rt_sigreturn_stub (void) -{ - __asm__ ("mov %0, %%g1\n\t" - "ta 0x10\n\t" - : /* no outputs */ - : "i" (__NR_rt_sigreturn)); -} - -static -inhibit_stack_protector -void -__sigreturn_stub (void) -{ - __asm__ ("mov %0, %%g1\n\t" - "ta 0x10\n\t" - : /* no outputs */ - : "i" (__NR_sigreturn)); -} diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S b/sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S new file mode 100644 index 0000000000..727cc94737 --- /dev/null +++ b/sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S @@ -0,0 +1,34 @@ +/* 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 + <https://www.gnu.org/licenses/>. */ + +#include <sysdep.h> + +/* These functions 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 0x10 +END (__rt_sigreturn_stub) + +ENTRY (__sigreturn_stub) + mov __NR_sigreturn, %g1 + ta 0x10 +END (__sigreturn_stub) diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c b/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c index 3b8be43c07..4772ec2553 100644 --- a/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c +++ b/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c @@ -22,21 +22,11 @@ #include <syscall.h> #include <sysdep.h> -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 <sysdeps/unix/sysv/linux/sigaction.c> - -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 + <https://www.gnu.org/licenses/>. */ + +#include <sysdep.h> + +/* 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)
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