From f33632ccd1dec3217583fcfdd965afb62954203c Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Thu, 30 Nov 2017 04:49:25 -0800 Subject: x86: Make a space in jmpbuf for shadow stack pointer To support Shadow Stack (SHSTK) in Intel Control-flow Enforcement Technology (CET) in setjmp/longjmp, we need to save shadow stack pointer in jmp_buf. The __saved_mask field in jmp_buf has type of __sigset_t. On Linux, __sigset_t is defined as #define _SIGSET_NWORDS (1024 / (8 * sizeof (unsigned long int))) typedef struct { unsigned long int __val[_SIGSET_NWORDS]; } __sigset_t; which is much bigger than expected by the __sigprocmask system call, which has typedef struct { unsigned long sig[_NSIG_WORDS]; } sigset_t; For Linux/x86, we can shrink __sigset_t used by __saved_mask in jmp_buf to add paddings for shadow stack pointer. As long as the new __sigset_t is not smaller than sigset_t expected by the __sigprocmask system call, it should work correctly. This patch adds an internal header file, , to define __jmp_buf_sigset_t for __saved_mask in jmp_buf for Linux/x86 with a space to store shadow stack pointer. It verifies __jmp_buf_sigset_t has the suitable size for the __sigprocmask system call. A run-time test, tst-saved_mask-1.c, is added to verify that size of __jmp_buf_sigset_t is sufficient. If its size is too small, the test fails with rt_sigprocmask(SIG_SETMASK, strace: umoven: short read (4 < 8) @0x7fa8aa28effc 0x7fa8aa28effc, NULL, 8) = -1 EFAULT (Bad address) rt_sigprocmask(SIG_SETMASK, strace: umoven: short read (4 < 8) @0x7fa8aa28effc 0x7fa8aa28effc, NULL, 8) = -1 EFAULT (Bad address) rt_sigprocmask(SIG_SETMASK, NULL, 0x7fa8aa28effc, 8) = -1 EFAULT (Bad address) exit_group(1) = ? Tested with build-many-glibcs.py. * debug/longjmp_chk.c: Include instead of . * setjmp/longjmp.c: Include instead of . (__libc_siglongjmp): Cast &env[0].__saved_mask to "sigset_t *". * setjmp/sigjmp.c: Include instead of . (__sigjmp_save): Cast &env[0].__saved_mask to "sigset_t *". * sysdeps/generic/setjmpP.h: New file. * sysdeps/unix/sysv/linux/x86/jmp_buf-ssp.sym: Likewise. * sysdeps/unix/sysv/linux/x86/setjmpP.h: Likewise. * sysdeps/unix/sysv/linux/x86/tst-saved_mask-1.c: Likewise. * sysdeps/unix/sysv/linux/x86/Makefile (gen-as-const-headers): Add jmp_buf-ssp.sym. (tests): Add tst-saved_mask-1. --- sysdeps/generic/setjmpP.h | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 sysdeps/generic/setjmpP.h (limited to 'sysdeps/generic/setjmpP.h') diff --git a/sysdeps/generic/setjmpP.h b/sysdeps/generic/setjmpP.h new file mode 100644 index 0000000000..a878ce6b35 --- /dev/null +++ b/sysdeps/generic/setjmpP.h @@ -0,0 +1,24 @@ +/* Internal header file for . Generic version. + Copyright (C) 2017 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 + . */ + +#ifndef _SETJMPP_H +#define _SETJMPP_H 1 + +#include + +#endif /* setjmpP.h */ -- cgit v1.2.3