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128 lines
4.0 KiB
C
128 lines
4.0 KiB
C
/* Internal header file for <setjmp.h>. Linux/x86 version.
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Copyright (C) 2017-2024 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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<https://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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#include <libc-pointer-arith.h>
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#include <sigsetops.h>
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/* <setjmp/setjmp.h> has
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struct __jmp_buf_tag
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{
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__jmp_buf __jmpbuf;
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int __mask_was_saved;
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__sigset_t __saved_mask;
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};
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struct __jmp_buf_tag is 32 bits aligned on i386 and is 64 bits
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aligned on x32 and x86-64. __saved_mask is aligned to 32 bits
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on i386/x32 without padding and is aligned to 64 bits on x86-64
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with 32 bit padding.
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and <nptl/descr.h> has
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struct pthread_unwind_buf
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{
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struct
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{
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__jmp_buf jmp_buf;
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int mask_was_saved;
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} cancel_jmp_buf[1];
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union
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{
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void *pad[4];
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struct
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{
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struct pthread_unwind_buf *prev;
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struct _pthread_cleanup_buffer *cleanup;
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int canceltype;
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} data;
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} priv;
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};
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struct pthread_unwind_buf is 32 bits aligned on i386 and 64 bits
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aligned on x32/x86-64. cancel_jmp_buf is aligned to 32 bits on
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i386 and is aligned to 64 bits on x32/x86-64.
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The pad array in struct pthread_unwind_buf is used by setjmp to save
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shadow stack register. The usable space in __saved_mask for sigset
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and shadow stack pointer:
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1. i386: The 4x4 byte pad array which can be used for 4 byte shadow
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stack pointer and maximum 12 byte sigset.
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2. x32: 4 byte padding + the 4x4 byte pad array which can be used
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for 8 byte shadow stack pointer and maximum 12 byte sigset.
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3. x86-64: The 4x8 byte pad array which can be used for 8 byte
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shadow stack pointer and maximum 24 byte sigset.
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NB: We use setjmp in thread cancellation and this saves the shadow
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stack register, but __libc_unwind_longjmp doesn't restore the shadow
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stack register since cancellation never returns after longjmp. */
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/* Number of bits per long. */
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#define _JUMP_BUF_SIGSET_BITS_PER_WORD (8 * sizeof (unsigned long int))
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/* The biggest signal number. As of kernel 4.14, x86 _NSIG is 64. The
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common maximum sigset for i386, x32 and x86-64 is 12 bytes (96 bits).
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Define it to 96 to leave some rooms for future use. */
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#define _JUMP_BUF_SIGSET_NSIG 96
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/* Number of longs to hold all signals. */
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#define _JUMP_BUF_SIGSET_NWORDS \
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(ALIGN_UP (_JUMP_BUF_SIGSET_NSIG, _JUMP_BUF_SIGSET_BITS_PER_WORD) \
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/ _JUMP_BUF_SIGSET_BITS_PER_WORD)
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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. NB: Shadow stack pointer
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must have the same alignment as __saved_mask. Otherwise
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offset of __saved_mask will be changed. */
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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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typedef struct
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{
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unsigned long int __val[__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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