1 /* Internal header file for <setjmp.h>. Linux/x86 version. 2 Copyright (C) 2017-2022 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 */ 128