1 /* Internal header file for <setjmp.h>. Linux/x86 version.
2 Copyright (C) 2017-2023 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 <https://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 #include <sigsetops.h>
25
26 /* <setjmp/setjmp.h> has
27
28 struct __jmp_buf_tag
29 {
30 __jmp_buf __jmpbuf;
31 int __mask_was_saved;
32 __sigset_t __saved_mask;
33 };
34
35 struct __jmp_buf_tag is 32 bits aligned on i386 and is 64 bits
36 aligned on x32 and x86-64. __saved_mask is aligned to 32 bits
37 on i386/x32 without padding and is aligned to 64 bits on x86-64
38 with 32 bit padding.
39
40 and <nptl/descr.h> has
41
42 struct pthread_unwind_buf
43 {
44 struct
45 {
46 __jmp_buf jmp_buf;
47 int mask_was_saved;
48 } cancel_jmp_buf[1];
49
50 union
51 {
52 void *pad[4];
53 struct
54 {
55 struct pthread_unwind_buf *prev;
56 struct _pthread_cleanup_buffer *cleanup;
57 int canceltype;
58 } data;
59 } priv;
60 };
61
62 struct pthread_unwind_buf is 32 bits aligned on i386 and 64 bits
63 aligned on x32/x86-64. cancel_jmp_buf is aligned to 32 bits on
64 i386 and is aligned to 64 bits on x32/x86-64.
65
66 The pad array in struct pthread_unwind_buf is used by setjmp to save
67 shadow stack register. The usable space in __saved_mask for sigset
68 and shadow stack pointer:
69 1. i386: The 4x4 byte pad array which can be used for 4 byte shadow
70 stack pointer and maximum 12 byte sigset.
71 2. x32: 4 byte padding + the 4x4 byte pad array which can be used
72 for 8 byte shadow stack pointer and maximum 12 byte sigset.
73 3. x86-64: The 4x8 byte pad array which can be used for 8 byte
74 shadow stack pointer and maximum 24 byte sigset.
75
76 NB: We use setjmp in thread cancellation and this saves the shadow
77 stack register, but __libc_unwind_longjmp doesn't restore the shadow
78 stack register since cancellation never returns after longjmp. */
79
80 /* Number of bits per long. */
81 #define _JUMP_BUF_SIGSET_BITS_PER_WORD (8 * sizeof (unsigned long int))
82 /* The biggest signal number. As of kernel 4.14, x86 _NSIG is 64. The
83 common maximum sigset for i386, x32 and x86-64 is 12 bytes (96 bits).
84 Define it to 96 to leave some rooms for future use. */
85 #define _JUMP_BUF_SIGSET_NSIG 96
86 /* Number of longs to hold all signals. */
87 #define _JUMP_BUF_SIGSET_NWORDS \
88 (ALIGN_UP (_JUMP_BUF_SIGSET_NSIG, _JUMP_BUF_SIGSET_BITS_PER_WORD) \
89 / _JUMP_BUF_SIGSET_BITS_PER_WORD)
90
91 typedef struct
92 {
93 unsigned long int __val[_JUMP_BUF_SIGSET_NWORDS];
94 } __jmp_buf_sigset_t;
95
96 typedef union
97 {
98 __sigset_t __saved_mask_compat;
99 struct
100 {
101 __jmp_buf_sigset_t __saved_mask;
102 /* Used for shadow stack pointer. NB: Shadow stack pointer
103 must have the same alignment as __saved_mask. Otherwise
104 offset of __saved_mask will be changed. */
105 unsigned long int __shadow_stack_pointer;
106 } __saved;
107 } __jmpbuf_arch_t;
108
109 #undef __sigset_t
110 #define __sigset_t __jmpbuf_arch_t
111 #include <setjmp.h>
112 #undef __saved_mask
113 #define __saved_mask __saved_mask.__saved.__saved_mask
114
115 #include <signal.h>
116
117 typedef struct
118 {
119 unsigned long int __val[__NSIG_WORDS];
120 } __sigprocmask_sigset_t;
121
122 extern jmp_buf ___buf;
123 extern __typeof (___buf[0].__saved_mask) ___saved_mask;
124 _Static_assert (sizeof (___saved_mask) >= sizeof (__sigprocmask_sigset_t),
125 "size of ___saved_mask < size of __sigprocmask_sigset_t");
126
127 #endif /* setjmpP.h */