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f33632ccd1
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, <setjmpP.h>, 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 <setjmpP.h> instead of
<setjmp.h>.
* setjmp/longjmp.c: Include <setjmpP.h> instead of <setjmp.h>.
(__libc_siglongjmp): Cast &env[0].__saved_mask to "sigset_t *".
* setjmp/sigjmp.c: Include <setjmpP.h> instead of <setjmp.h>.
(__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.
68 lines
2.1 KiB
C
68 lines
2.1 KiB
C
/* Internal header file for <setjmp.h>. Linux/x86 version.
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Copyright (C) 2017 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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<http://www.gnu.org/licenses/>. */
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#ifndef _SETJMPP_H
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#define _SETJMPP_H 1
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#include <bits/types/__sigset_t.h>
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/* The biggest signal number + 1. As of kernel 4.14, x86 _NSIG is 64.
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Define it to 513 to leave some rooms for future use. */
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#define _JUMP_BUF_SIGSET_NSIG 513
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/* Number of longs to hold all signals. */
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#define _JUMP_BUF_SIGSET_NWORDS \
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((_JUMP_BUF_SIGSET_NSIG - 1 + 7) / (8 * sizeof (unsigned long int)))
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typedef struct
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{
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unsigned long int __val[_JUMP_BUF_SIGSET_NWORDS];
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} __jmp_buf_sigset_t;
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typedef union
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{
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__sigset_t __saved_mask_compat;
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struct
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{
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__jmp_buf_sigset_t __saved_mask;
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/* Used for shadow stack pointer. */
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unsigned long int __shadow_stack_pointer;
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} __saved;
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} __jmpbuf_arch_t;
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#undef __sigset_t
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#define __sigset_t __jmpbuf_arch_t
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#include <setjmp.h>
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#undef __saved_mask
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#define __saved_mask __saved_mask.__saved.__saved_mask
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#include <signal.h>
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#define _SIGPROCMASK_NSIG_WORDS (_NSIG / (8 * sizeof (unsigned long int)))
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typedef struct
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{
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unsigned long int __val[_SIGPROCMASK_NSIG_WORDS];
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} __sigprocmask_sigset_t;
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extern jmp_buf ___buf;
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extern __typeof (___buf[0].__saved_mask) ___saved_mask;
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_Static_assert (sizeof (___saved_mask) >= sizeof (__sigprocmask_sigset_t),
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"size of ___saved_mask < size of __sigprocmask_sigset_t");
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#endif /* setjmpP.h */
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