1/* Internal header file for <setjmp.h>. Linux/x86 version.
2 Copyright (C) 2017-2019 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#ifndef _SETJMPP_H
20#define _SETJMPP_H 1
21
22#include <bits/types/__sigset_t.h>
23#include <libc-pointer-arith.h>
24
25/* <setjmp/setjmp.h> has
26
27struct __jmp_buf_tag
28 {
29 __jmp_buf __jmpbuf;
30 int __mask_was_saved;
31 __sigset_t __saved_mask;
32 };
33
34 struct __jmp_buf_tag is 32 bits aligned on i386 and is 64 bits
35 aligned on x32 and x86-64. __saved_mask is aligned to 32 bits
36 on i386/x32 without padding and is aligned to 64 bits on x86-64
37 with 32 bit padding.
38
39 and <nptl/descr.h> has
40
41struct pthread_unwind_buf
42{
43 struct
44 {
45 __jmp_buf jmp_buf;
46 int mask_was_saved;
47 } cancel_jmp_buf[1];
48
49 union
50 {
51 void *pad[4];
52 struct
53 {
54 struct pthread_unwind_buf *prev;
55 struct _pthread_cleanup_buffer *cleanup;
56 int canceltype;
57 } data;
58 } priv;
59};
60
61 struct pthread_unwind_buf is 32 bits aligned on i386 and 64 bits
62 aligned on x32/x86-64. cancel_jmp_buf is aligned to 32 bits on
63 i386 and is aligned to 64 bits on x32/x86-64.
64
65 The pad array in struct pthread_unwind_buf is used by setjmp to save
66 shadow stack register. The usable space in __saved_mask for sigset
67 and shadow stack pointer:
68 1. i386: The 4x4 byte pad array which can be used for 4 byte shadow
69 stack pointer and maximum 12 byte sigset.
70 2. x32: 4 byte padding + the 4x4 byte pad array which can be used
71 for 8 byte shadow stack pointer and maximum 12 byte sigset.
72 3. x86-64: The 4x8 byte pad array which can be used for 8 byte
73 shadow stack pointer and maximum 24 byte sigset.
74
75 NB: We use setjmp in thread cancellation and this saves the shadow
76 stack register, but __libc_unwind_longjmp doesn't restore the shadow
77 stack register since cancellation never returns after longjmp. */
78
79/* Number of bits per long. */
80#define _JUMP_BUF_SIGSET_BITS_PER_WORD (8 * sizeof (unsigned long int))
81/* The biggest signal number. As of kernel 4.14, x86 _NSIG is 64. The
82 common maximum sigset for i386, x32 and x86-64 is 12 bytes (96 bits).
83 Define it to 96 to leave some rooms for future use. */
84#define _JUMP_BUF_SIGSET_NSIG 96
85/* Number of longs to hold all signals. */
86#define _JUMP_BUF_SIGSET_NWORDS \
87 (ALIGN_UP (_JUMP_BUF_SIGSET_NSIG, _JUMP_BUF_SIGSET_BITS_PER_WORD) \
88 / _JUMP_BUF_SIGSET_BITS_PER_WORD)
89
90typedef struct
91 {
92 unsigned long int __val[_JUMP_BUF_SIGSET_NWORDS];
93 } __jmp_buf_sigset_t;
94
95typedef union
96 {
97 __sigset_t __saved_mask_compat;
98 struct
99 {
100 __jmp_buf_sigset_t __saved_mask;
101 /* Used for shadow stack pointer. NB: Shadow stack pointer
102 must have the same alignment as __saved_mask. Otherwise
103 offset of __saved_mask will be changed. */
104 unsigned long int __shadow_stack_pointer;
105 } __saved;
106 } __jmpbuf_arch_t;
107
108#undef __sigset_t
109#define __sigset_t __jmpbuf_arch_t
110#include <setjmp.h>
111#undef __saved_mask
112#define __saved_mask __saved_mask.__saved.__saved_mask
113
114#include <signal.h>
115
116#define _SIGPROCMASK_NSIG_WORDS (_NSIG / (8 * sizeof (unsigned long int)))
117
118typedef struct
119 {
120 unsigned long int __val[_SIGPROCMASK_NSIG_WORDS];
121 } __sigprocmask_sigset_t;
122
123extern jmp_buf ___buf;
124extern __typeof (___buf[0].__saved_mask) ___saved_mask;
125_Static_assert (sizeof (___saved_mask) >= sizeof (__sigprocmask_sigset_t),
126 "size of ___saved_mask < size of __sigprocmask_sigset_t");
127
128#endif /* setjmpP.h */
129