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/* Internal header file for <setjmp.h>. Linux/x86 version.
Copyright (C) 2017-2020 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/>. */
#ifndef _SETJMPP_H
#define _SETJMPP_H 1
#include <bits/types/__sigset_t.h>
#include <libc-pointer-arith.h>
/* <setjmp/setjmp.h> has
struct __jmp_buf_tag
{
__jmp_buf __jmpbuf;
int __mask_was_saved;
__sigset_t __saved_mask;
};
struct __jmp_buf_tag is 32 bits aligned on i386 and is 64 bits
aligned on x32 and x86-64. __saved_mask is aligned to 32 bits
on i386/x32 without padding and is aligned to 64 bits on x86-64
with 32 bit padding.
and <nptl/descr.h> has
struct pthread_unwind_buf
{
struct
{
__jmp_buf jmp_buf;
int mask_was_saved;
} cancel_jmp_buf[1];
union
{
void *pad[4];
struct
{
struct pthread_unwind_buf *prev;
struct _pthread_cleanup_buffer *cleanup;
int canceltype;
} data;
} priv;
};
struct pthread_unwind_buf is 32 bits aligned on i386 and 64 bits
aligned on x32/x86-64. cancel_jmp_buf is aligned to 32 bits on
i386 and is aligned to 64 bits on x32/x86-64.
The pad array in struct pthread_unwind_buf is used by setjmp to save
shadow stack register. The usable space in __saved_mask for sigset
and shadow stack pointer:
1. i386: The 4x4 byte pad array which can be used for 4 byte shadow
stack pointer and maximum 12 byte sigset.
2. x32: 4 byte padding + the 4x4 byte pad array which can be used
for 8 byte shadow stack pointer and maximum 12 byte sigset.
3. x86-64: The 4x8 byte pad array which can be used for 8 byte
shadow stack pointer and maximum 24 byte sigset.
NB: We use setjmp in thread cancellation and this saves the shadow
stack register, but __libc_unwind_longjmp doesn't restore the shadow
stack register since cancellation never returns after longjmp. */
/* Number of bits per long. */
#define _JUMP_BUF_SIGSET_BITS_PER_WORD (8 * sizeof (unsigned long int))
/* The biggest signal number. As of kernel 4.14, x86 _NSIG is 64. The
common maximum sigset for i386, x32 and x86-64 is 12 bytes (96 bits).
Define it to 96 to leave some rooms for future use. */
#define _JUMP_BUF_SIGSET_NSIG 96
/* Number of longs to hold all signals. */
#define _JUMP_BUF_SIGSET_NWORDS \
(ALIGN_UP (_JUMP_BUF_SIGSET_NSIG, _JUMP_BUF_SIGSET_BITS_PER_WORD) \
/ _JUMP_BUF_SIGSET_BITS_PER_WORD)
typedef struct
{
unsigned long int __val[_JUMP_BUF_SIGSET_NWORDS];
} __jmp_buf_sigset_t;
typedef union
{
__sigset_t __saved_mask_compat;
struct
{
__jmp_buf_sigset_t __saved_mask;
/* Used for shadow stack pointer. NB: Shadow stack pointer
must have the same alignment as __saved_mask. Otherwise
offset of __saved_mask will be changed. */
unsigned long int __shadow_stack_pointer;
} __saved;
} __jmpbuf_arch_t;
#undef __sigset_t
#define __sigset_t __jmpbuf_arch_t
#include <setjmp.h>
#undef __saved_mask
#define __saved_mask __saved_mask.__saved.__saved_mask
#include <signal.h>
#define _SIGPROCMASK_NSIG_WORDS (_NSIG / (8 * sizeof (unsigned long int)))
typedef struct
{
unsigned long int __val[_SIGPROCMASK_NSIG_WORDS];
} __sigprocmask_sigset_t;
extern jmp_buf ___buf;
extern __typeof (___buf[0].__saved_mask) ___saved_mask;
_Static_assert (sizeof (___saved_mask) >= sizeof (__sigprocmask_sigset_t),
"size of ___saved_mask < size of __sigprocmask_sigset_t");
#endif /* setjmpP.h */
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