1 /* DWARF2 EH unwinding support for GNU Hurd: x86.
2 Copyright (C) 2020 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 #define MD_FALLBACK_FRAME_STATE_FOR x86_gnu_fallback_frame_state
34
35 static _Unwind_Reason_Code
x86_gnu_fallback_frame_state(struct _Unwind_Context * context,_Unwind_FrameState * fs)36 x86_gnu_fallback_frame_state
37 (struct _Unwind_Context *context, _Unwind_FrameState *fs)
38 {
39 struct handler_args {
40 int signo;
41 union
42 {
43 struct
44 {
45 long int sigcode;
46 struct sigcontext *scp;
47 } legacy;
48 struct
49 {
50 siginfo_t *siginfop;
51 ucontext_t *uctxp;
52 } posix;
53 };
54 } *handler_args;
55 long int sigcode;
56 unsigned long usp;
57
58 /*
59 * i386 sigtramp frame we are looking for follows.
60 * (see glibc/sysdeps/mach/hurd/i386/trampoline.c assembly)
61 *
62 * rpc_wait_trampoline:
63 * 0: b8 e7 ff ff ff mov $-25,%eax mach_msg_trap
64 * 5: 9a 00 00 00 00 07 00 lcall $7,$0
65 * 12: 89 01 movl %eax, (%ecx)
66 * 14: 89 dc movl %ebx, %esp switch to signal stack
67 *
68 * trampoline:
69 * 16: ff d2 call *%edx call the handler function
70 * RA HERE
71 * 18: 83 c4 0c addl $12, %esp pop its args
72 * 21: c3 ret return to sigreturn
73 *
74 * firewall:
75 * 22: f4 hlt
76 */
77
78 if (!( *(unsigned int *)(context->ra ) == 0xc30cc483
79 && *(unsigned char *)(context->ra + 4) == 0xf4
80
81 && *(unsigned int *)(context->ra - 4) == 0xd2ffdc89
82 && *(unsigned int *)(context->ra - 8) == 0x01890007
83 && *(unsigned int *)(context->ra - 12) == 0x00000000
84 && *(unsigned int *)(context->ra - 16) == 0x9affffff
85 && *(unsigned short *)(context->ra - 18) == 0xe7b8))
86 return _URC_END_OF_STACK;
87
88 handler_args = context->cfa;
89 sigcode = handler_args->legacy.sigcode;
90 if (sigcode >= -16 && sigcode < 4096)
91 {
92 /* This cannot be a SIGINFO pointer, assume legacy. */
93 struct sigcontext *scp = handler_args->legacy.scp;
94 usp = scp->sc_uesp;
95
96 fs->regs.reg[0].loc.offset = (unsigned long)&scp->sc_eax - usp;
97 fs->regs.reg[1].loc.offset = (unsigned long)&scp->sc_ecx - usp;
98 fs->regs.reg[2].loc.offset = (unsigned long)&scp->sc_edx - usp;
99 fs->regs.reg[3].loc.offset = (unsigned long)&scp->sc_ebx - usp;
100 fs->regs.reg[5].loc.offset = (unsigned long)&scp->sc_ebp - usp;
101 fs->regs.reg[6].loc.offset = (unsigned long)&scp->sc_esi - usp;
102 fs->regs.reg[7].loc.offset = (unsigned long)&scp->sc_edi - usp;
103 fs->regs.reg[8].loc.offset = (unsigned long)&scp->sc_eip - usp;
104 }
105 else
106 {
107 /* This is not a valid sigcode, assume SIGINFO. */
108 ucontext_t *uctxp = handler_args->posix.uctxp;
109 gregset_t *gregset = &uctxp->uc_mcontext.gregs;
110 usp = (*gregset)[REG_UESP];
111
112 fs->regs.reg[0].loc.offset = (unsigned long)&(*gregset)[REG_EAX] - usp;
113 fs->regs.reg[1].loc.offset = (unsigned long)&(*gregset)[REG_ECX] - usp;
114 fs->regs.reg[2].loc.offset = (unsigned long)&(*gregset)[REG_EDX] - usp;
115 fs->regs.reg[3].loc.offset = (unsigned long)&(*gregset)[REG_EBX] - usp;
116 fs->regs.reg[5].loc.offset = (unsigned long)&(*gregset)[REG_EBP] - usp;
117 fs->regs.reg[6].loc.offset = (unsigned long)&(*gregset)[REG_ESI] - usp;
118 fs->regs.reg[7].loc.offset = (unsigned long)&(*gregset)[REG_EDI] - usp;
119 fs->regs.reg[8].loc.offset = (unsigned long)&(*gregset)[REG_EIP] - usp;
120 }
121
122 fs->regs.cfa_how = CFA_REG_OFFSET;
123 fs->regs.cfa_reg = 4;
124 fs->regs.cfa_offset = usp - (unsigned long) context->cfa;
125
126 fs->regs.reg[0].how = REG_SAVED_OFFSET;
127 fs->regs.reg[1].how = REG_SAVED_OFFSET;
128 fs->regs.reg[2].how = REG_SAVED_OFFSET;
129 fs->regs.reg[3].how = REG_SAVED_OFFSET;
130 fs->regs.reg[5].how = REG_SAVED_OFFSET;
131 fs->regs.reg[6].how = REG_SAVED_OFFSET;
132 fs->regs.reg[7].how = REG_SAVED_OFFSET;
133 fs->regs.reg[8].how = REG_SAVED_OFFSET;
134
135 fs->retaddr_column = 8;
136 fs->signal_frame = 1;
137
138 return _URC_NO_REASON;
139 }
140
141 #endif /* ifndef inhibit_libc */
142