1 /* DWARF2 EH unwinding support for GNU Hurd: x86.
2 Copyright (C) 2020-2023 Free Software Foundation, Inc.
3 Contributed by Samuel Thibault <samuel.thibault@gnu.org>
4
5 This file is part of GCC.
6
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
10 any later version.
11
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 Under Section 7 of GPL version 3, you are granted additional
18 permissions described in the GCC Runtime Library Exception, version
19 3.1, as published by the Free Software Foundation.
20
21 You should have received a copy of the GNU General Public License and
22 a copy of the GCC Runtime Library Exception along with this program;
23 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 <http://www.gnu.org/licenses/>. */
25
26 /* Do code reading to identify a signal frame, and set the frame
27 state data appropriately. See unwind-dw2.c for the structs. */
28
29 #ifndef inhibit_libc
30
31 #include <signal.h>
32
33 #ifdef __x86_64__
34
35 /*
36 * TODO: support for 64 bits needs to be implemented.
37 */
38
39 #else /* ifdef __x86_64__ */
40
41 #define MD_FALLBACK_FRAME_STATE_FOR x86_gnu_fallback_frame_state
42
43 static _Unwind_Reason_Code
44 x86_gnu_fallback_frame_state
45 (struct _Unwind_Context *context, _Unwind_FrameState *fs)
46 {
47 struct handler_args {
48 int signo;
49 union
50 {
51 struct
52 {
53 long int sigcode;
54 struct sigcontext *scp;
55 } legacy;
56 struct
57 {
58 siginfo_t *siginfop;
59 ucontext_t *uctxp;
60 } posix;
61 };
62 } *handler_args;
63 long int sigcode;
64 unsigned long usp;
65
66 /*
67 * i386 sigtramp frame we are looking for follows.
68 * (see glibc/sysdeps/mach/hurd/i386/trampoline.c assembly)
69 *
70 * rpc_wait_trampoline:
71 * 0: b8 e7 ff ff ff mov $-25,%eax mach_msg_trap
72 * 5: 9a 00 00 00 00 07 00 lcall $7,$0
73 * 12: 89 01 movl %eax, (%ecx)
74 * 14: 89 dc movl %ebx, %esp switch to signal stack
75 *
76 * trampoline:
77 * 16: ff d2 call *%edx call the handler function
78 * RA HERE
79 * 18: 83 c4 0c addl $12, %esp pop its args
80 * 21: c3 ret return to sigreturn
81 *
82 * firewall:
83 * 22: f4 hlt
84 */
85
86 if (!( *(unsigned int *)(context->ra ) == 0xc30cc483
87 && *(unsigned char *)(context->ra + 4) == 0xf4
88
89 && *(unsigned int *)(context->ra - 4) == 0xd2ffdc89
90 && *(unsigned int *)(context->ra - 8) == 0x01890007
91 && *(unsigned int *)(context->ra - 12) == 0x00000000
92 && *(unsigned int *)(context->ra - 16) == 0x9affffff
93 && *(unsigned short *)(context->ra - 18) == 0xe7b8))
94 return _URC_END_OF_STACK;
95
96 handler_args = context->cfa;
97 sigcode = handler_args->legacy.sigcode;
98 if (sigcode >= -16 && sigcode < 4096)
99 {
100 /* This cannot be a SIGINFO pointer, assume legacy. */
101 struct sigcontext *scp = handler_args->legacy.scp;
102 usp = scp->sc_uesp;
103
104 fs->regs.reg[0].loc.offset = (unsigned long)&scp->sc_eax - usp;
105 fs->regs.reg[1].loc.offset = (unsigned long)&scp->sc_ecx - usp;
106 fs->regs.reg[2].loc.offset = (unsigned long)&scp->sc_edx - usp;
107 fs->regs.reg[3].loc.offset = (unsigned long)&scp->sc_ebx - usp;
108 fs->regs.reg[5].loc.offset = (unsigned long)&scp->sc_ebp - usp;
109 fs->regs.reg[6].loc.offset = (unsigned long)&scp->sc_esi - usp;
110 fs->regs.reg[7].loc.offset = (unsigned long)&scp->sc_edi - usp;
111 fs->regs.reg[8].loc.offset = (unsigned long)&scp->sc_eip - usp;
112 }
113 else
114 {
115 /* This is not a valid sigcode, assume SIGINFO. */
116 ucontext_t *uctxp = handler_args->posix.uctxp;
117 gregset_t *gregset = &uctxp->uc_mcontext.gregs;
118 usp = (*gregset)[REG_UESP];
119
120 fs->regs.reg[0].loc.offset = (unsigned long)&(*gregset)[REG_EAX] - usp;
121 fs->regs.reg[1].loc.offset = (unsigned long)&(*gregset)[REG_ECX] - usp;
122 fs->regs.reg[2].loc.offset = (unsigned long)&(*gregset)[REG_EDX] - usp;
123 fs->regs.reg[3].loc.offset = (unsigned long)&(*gregset)[REG_EBX] - usp;
124 fs->regs.reg[5].loc.offset = (unsigned long)&(*gregset)[REG_EBP] - usp;
125 fs->regs.reg[6].loc.offset = (unsigned long)&(*gregset)[REG_ESI] - usp;
126 fs->regs.reg[7].loc.offset = (unsigned long)&(*gregset)[REG_EDI] - usp;
127 fs->regs.reg[8].loc.offset = (unsigned long)&(*gregset)[REG_EIP] - usp;
128 }
129
130 fs->regs.cfa_how = CFA_REG_OFFSET;
131 fs->regs.cfa_reg = 4;
132 fs->regs.cfa_offset = usp - (unsigned long) context->cfa;
133
134 fs->regs.how[0] = REG_SAVED_OFFSET;
135 fs->regs.how[1] = REG_SAVED_OFFSET;
136 fs->regs.how[2] = REG_SAVED_OFFSET;
137 fs->regs.how[3] = REG_SAVED_OFFSET;
138 fs->regs.how[5] = REG_SAVED_OFFSET;
139 fs->regs.how[6] = REG_SAVED_OFFSET;
140 fs->regs.how[7] = REG_SAVED_OFFSET;
141 fs->regs.how[8] = REG_SAVED_OFFSET;
142
143 fs->retaddr_column = 8;
144 fs->signal_frame = 1;
145
146 return _URC_NO_REASON;
147 }
148
149 #endif /* ifdef __x86_64__ */
150
151 #endif /* ifndef inhibit_libc */