1/* POSIX.1 `sigaction' call for Linux/x86-64.
2 Copyright (C) 2001-2023 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#include <signal.h>
20#define SA_RESTORER 0x04000000
21
22extern void restore_rt (void) asm ("__restore_rt") attribute_hidden;
23
24#define SET_SA_RESTORER(kact, act) \
25 (kact)->sa_flags = (act)->sa_flags | SA_RESTORER; \
26 (kact)->sa_restorer = &restore_rt
27
28#define RESET_SA_RESTORER(act, kact) \
29 (act)->sa_restorer = (kact)->sa_restorer
30
31#include <kernel_sigaction.h>
32
33#include <sysdeps/unix/sysv/linux/libc_sigaction.c>
34
35/* NOTE: Please think twice before making any changes to the bits of
36 code below. GDB needs some intimate knowledge about it to
37 recognize them as signal trampolines, and make backtraces through
38 signal handlers work right. Important are both the names
39 (__restore_rt) and the exact instruction sequence.
40 If you ever feel the need to make any changes, please notify the
41 appropriate GDB maintainer.
42
43 The unwind information starts a byte before __restore_rt, so that
44 it is found when unwinding, to get an address the unwinder assumes
45 will be in the middle of a call instruction. See the Linux kernel
46 (the i386 vsyscall, in particular) for an explanation of the complex
47 unwind information used here in order to get the traditional CFA.
48 We do not restore cs - it's only stored as two bytes here so that's
49 a bit tricky. We don't use the gas cfi directives, so that we can
50 reliably add .cfi_signal_frame. */
51
52#include "ucontext_i.h"
53
54#define do_cfa_expr \
55 " .byte 0x0f\n" /* DW_CFA_def_cfa_expression */ \
56 " .uleb128 2f-1f\n" /* length */ \
57 "1: .byte 0x77\n" /* DW_OP_breg7 */ \
58 " .sleb128 " CFI_STRINGIFY (oRSP) "\n" \
59 " .byte 0x06\n" /* DW_OP_deref */ \
60 "2:"
61
62#define do_expr(regno, offset) \
63 " .byte 0x10\n" /* DW_CFA_expression */ \
64 " .uleb128 " CFI_STRINGIFY (regno) "\n" \
65 " .uleb128 2f-1f\n" /* length */ \
66 "1: .byte 0x77\n" /* DW_OP_breg7 */ \
67 " .sleb128 " CFI_STRINGIFY (offset) "\n" \
68 "2:"
69
70#define RESTORE(name, syscall) RESTORE2 (name, syscall)
71# define RESTORE2(name, syscall) \
72asm \
73 ( \
74 /* `nop' for debuggers assuming `call' should not disalign the code. */ \
75 " nop\n" \
76 ".align 16\n" \
77 ".LSTART_" #name ":\n" \
78 " .type __" #name ",@function\n" \
79 "__" #name ":\n" \
80 " movq $" #syscall ", %rax\n" \
81 " syscall\n" \
82 ".LEND_" #name ":\n" \
83 ".section .eh_frame,\"a\",@progbits\n" \
84 ".LSTARTFRAME_" #name ":\n" \
85 " .long .LENDCIE_" #name "-.LSTARTCIE_" #name "\n" \
86 ".LSTARTCIE_" #name ":\n" \
87 " .long 0\n" /* CIE ID */ \
88 " .byte 1\n" /* Version number */ \
89 " .string \"zRS\"\n" /* NUL-terminated augmentation string */ \
90 " .uleb128 1\n" /* Code alignment factor */ \
91 " .sleb128 -8\n" /* Data alignment factor */ \
92 " .uleb128 16\n" /* Return address register column (rip) */ \
93 /* Augmentation value length */ \
94 " .uleb128 .LENDAUGMNT_" #name "-.LSTARTAUGMNT_" #name "\n" \
95 ".LSTARTAUGMNT_" #name ":\n" \
96 " .byte 0x1b\n" /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */ \
97 ".LENDAUGMNT_" #name ":\n" \
98 " .align " LP_SIZE "\n" \
99 ".LENDCIE_" #name ":\n" \
100 " .long .LENDFDE_" #name "-.LSTARTFDE_" #name "\n" /* FDE len */ \
101 ".LSTARTFDE_" #name ":\n" \
102 " .long .LSTARTFDE_" #name "-.LSTARTFRAME_" #name "\n" /* CIE */ \
103 /* `LSTART_' is subtracted 1 as debuggers assume a `call' here. */ \
104 " .long (.LSTART_" #name "-1)-.\n" /* PC-relative start addr. */ \
105 " .long .LEND_" #name "-(.LSTART_" #name "-1)\n" \
106 " .uleb128 0\n" /* FDE augmentation length */ \
107 do_cfa_expr \
108 do_expr (8 /* r8 */, oR8) \
109 do_expr (9 /* r9 */, oR9) \
110 do_expr (10 /* r10 */, oR10) \
111 do_expr (11 /* r11 */, oR11) \
112 do_expr (12 /* r12 */, oR12) \
113 do_expr (13 /* r13 */, oR13) \
114 do_expr (14 /* r14 */, oR14) \
115 do_expr (15 /* r15 */, oR15) \
116 do_expr (5 /* rdi */, oRDI) \
117 do_expr (4 /* rsi */, oRSI) \
118 do_expr (6 /* rbp */, oRBP) \
119 do_expr (3 /* rbx */, oRBX) \
120 do_expr (1 /* rdx */, oRDX) \
121 do_expr (0 /* rax */, oRAX) \
122 do_expr (2 /* rcx */, oRCX) \
123 do_expr (7 /* rsp */, oRSP) \
124 do_expr (16 /* rip */, oRIP) \
125 /* libgcc-4.1.1 has only `DWARF_FRAME_REGISTERS == 17'. */ \
126 /* do_expr (49 |* rflags *|, oEFL) */ \
127 /* `cs'/`ds'/`fs' are unaligned and a different size. */ \
128 /* gas: Error: register save offset not a multiple of 8 */ \
129 " .align " LP_SIZE "\n" \
130 ".LENDFDE_" #name ":\n" \
131 " .previous\n" \
132 );
133/* The return code for realtime-signals. */
134RESTORE (restore_rt, __NR_rt_sigreturn)
135