1 /* DWARF2 EH unwinding support for FreeBSD: AMD x86-64 and x86.
2 Copyright (C) 2015-2023 Free Software Foundation, Inc.
3 Contributed by John Marino <gnugcc@marino.st>
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 #include <sys/types.h>
30 #include <signal.h>
31 #include <unistd.h>
32 #include <sys/sysctl.h>
33 #include <sys/ucontext.h>
34 #include <sys/user.h>
35 #include <machine/sigframe.h>
36
37 #define REG_NAME(reg) sf_uc.uc_mcontext.mc_## reg
38
39 #ifdef __x86_64__
40 #define MD_FALLBACK_FRAME_STATE_FOR x86_64_freebsd_fallback_frame_state
41
42 #ifdef KERN_PROC_SIGTRAMP
43 /* FreeBSD past 9.3 provides a kern.proc.sigtramp.<pid> sysctl that
44 returns the location of the signal trampoline. Use this to find
45 out whether we're in a trampoline.
46 */
47 static int
48 x86_64_outside_sigtramp_range (unsigned char *pc)
49 {
50 static int sigtramp_range_determined = 0;
51 static unsigned char *sigtramp_start, *sigtramp_end;
52
53 if (sigtramp_range_determined == 0)
54 {
55 struct kinfo_sigtramp kst = {0};
56 size_t len = sizeof (kst);
57 int mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_SIGTRAMP, getpid() };
58
59 sigtramp_range_determined = 1;
60 if (sysctl (mib, 4, &kst, &len, NULL, 0) == 0)
61 {
62 sigtramp_range_determined = 2;
63 sigtramp_start = kst.ksigtramp_start;
64 sigtramp_end = kst.ksigtramp_end;
65 }
66 }
67 if (sigtramp_range_determined < 2) /* sysctl failed if < 2 */
68 return 1;
69
70 return (pc < sigtramp_start || pc >= sigtramp_end);
71 }
72 #endif
73
74 static _Unwind_Reason_Code
75 x86_64_freebsd_fallback_frame_state
76 (struct _Unwind_Context *context, _Unwind_FrameState *fs)
77 {
78 struct sigframe *sf;
79 long new_cfa;
80
81 #ifndef KERN_PROC_SIGTRAMP
82 /* Prior to FreeBSD 9, the signal trampoline was located immediately
83 before the ps_strings. To support non-executable stacks on AMD64,
84 the sigtramp was moved to a shared page for FreeBSD 9. Unfortunately
85 this means looking frame patterns again (sys/amd64/amd64/sigtramp.S)
86 rather than using the robust and convenient KERN_PS_STRINGS trick.
87
88 <pc + 00>: lea 0x10(%rsp),%rdi
89 <pc + 05>: pushq $0x0
90 <pc + 17>: mov $0x1a1,%rax
91 <pc + 14>: syscall
92
93 If we can't find this pattern, we're at the end of the stack.
94 */
95
96 if (!( *(unsigned int *)(context->ra) == 0x247c8d48
97 && *(unsigned int *)(context->ra + 4) == 0x48006a10
98 && *(unsigned int *)(context->ra + 8) == 0x01a1c0c7
99 && *(unsigned int *)(context->ra + 12) == 0x050f0000 ))
100 return _URC_END_OF_STACK;
101 #else
102 if (x86_64_outside_sigtramp_range(context->ra))
103 return _URC_END_OF_STACK;
104 #endif
105
106 sf = (struct sigframe *) context->cfa;
107 new_cfa = sf->REG_NAME(rsp);
108 fs->regs.cfa_how = CFA_REG_OFFSET;
109 fs->regs.cfa_reg = __LIBGCC_STACK_POINTER_REGNUM__;
110 fs->regs.cfa_offset = new_cfa - (long) context->cfa;
111
112 /* The SVR4 register numbering macros aren't usable in libgcc. */
113 fs->regs.how[0] = REG_SAVED_OFFSET;
114 fs->regs.reg[0].loc.offset = (long)&sf->REG_NAME(rax) - new_cfa;
115 fs->regs.how[1] = REG_SAVED_OFFSET;
116 fs->regs.reg[1].loc.offset = (long)&sf->REG_NAME(rdx) - new_cfa;
117 fs->regs.how[2] = REG_SAVED_OFFSET;
118 fs->regs.reg[2].loc.offset = (long)&sf->REG_NAME(rcx) - new_cfa;
119 fs->regs.how[3] = REG_SAVED_OFFSET;
120 fs->regs.reg[3].loc.offset = (long)&sf->REG_NAME(rbx) - new_cfa;
121 fs->regs.how[4] = REG_SAVED_OFFSET;
122 fs->regs.reg[4].loc.offset = (long)&sf->REG_NAME(rsi) - new_cfa;
123 fs->regs.how[5] = REG_SAVED_OFFSET;
124 fs->regs.reg[5].loc.offset = (long)&sf->REG_NAME(rdi) - new_cfa;
125 fs->regs.how[6] = REG_SAVED_OFFSET;
126 fs->regs.reg[6].loc.offset = (long)&sf->REG_NAME(rbp) - new_cfa;
127 fs->regs.how[8] = REG_SAVED_OFFSET;
128 fs->regs.reg[8].loc.offset = (long)&sf->REG_NAME(r8) - new_cfa;
129 fs->regs.how[9] = REG_SAVED_OFFSET;
130 fs->regs.reg[9].loc.offset = (long)&sf->REG_NAME(r9) - new_cfa;
131 fs->regs.how[10] = REG_SAVED_OFFSET;
132 fs->regs.reg[10].loc.offset = (long)&sf->REG_NAME(r10) - new_cfa;
133 fs->regs.how[11] = REG_SAVED_OFFSET;
134 fs->regs.reg[11].loc.offset = (long)&sf->REG_NAME(r11) - new_cfa;
135 fs->regs.how[12] = REG_SAVED_OFFSET;
136 fs->regs.reg[12].loc.offset = (long)&sf->REG_NAME(r12) - new_cfa;
137 fs->regs.how[13] = REG_SAVED_OFFSET;
138 fs->regs.reg[13].loc.offset = (long)&sf->REG_NAME(r13) - new_cfa;
139 fs->regs.how[14] = REG_SAVED_OFFSET;
140 fs->regs.reg[14].loc.offset = (long)&sf->REG_NAME(r14) - new_cfa;
141 fs->regs.how[15] = REG_SAVED_OFFSET;
142 fs->regs.reg[15].loc.offset = (long)&sf->REG_NAME(r15) - new_cfa;
143 fs->regs.how[16] = REG_SAVED_OFFSET;
144 fs->regs.reg[16].loc.offset = (long)&sf->REG_NAME(rip) - new_cfa;
145 fs->retaddr_column = 16;
146 fs->signal_frame = 1;
147 return _URC_NO_REASON;
148 }
149
150 #else /* Next section is for i386 */
151
152 #define MD_FALLBACK_FRAME_STATE_FOR x86_freebsd_fallback_frame_state
153
154 /*
155 * We can't use KERN_PS_STRINGS anymore if we want to support FreeBSD32
156 * compat on AMD64. The sigtramp is in a shared page in that case so the
157 * x86_sigtramp_range only works on a true i386 system. We have to
158 * search for the sigtramp frame if we want it working everywhere.
159 */
160
161 static _Unwind_Reason_Code
162 x86_freebsd_fallback_frame_state
163 (struct _Unwind_Context *context, _Unwind_FrameState *fs)
164 {
165 struct sigframe *sf;
166 long new_cfa;
167
168 /*
169 * i386 sigtramp frame we are looking for follows.
170 * Apparently PSL_VM is variable, so we can't look past context->ra + 4
171 * <sigcode>:
172 * 0: ff 54 24 10 call *0x10(%esp) *SIGF_HANDLER
173 * 4: 8d 44 24 20 lea 0x20(%esp),%eax SIGF_UC
174 * 8: 50 push %eax
175 * 9: f7 40 54 00 00 02 00 testl $0x20000,0x54(%eax) $PSL_VM
176 * 10: 75 03 jne 15 <sigcode+0x15>
177 * 12: 8e 68 14 mov 0x14(%eax),%gs UC_GS
178 * 15: b8 a1 01 00 00 mov 0x1a1,%eax $SYS_sigreturn
179 */
180
181 if (!( *(unsigned int *)(context->ra - 4) == 0x102454ff
182 && *(unsigned int *)(context->ra) == 0x2024448d ))
183 return _URC_END_OF_STACK;
184
185 sf = (struct sigframe *) context->cfa;
186 new_cfa = sf->REG_NAME(esp);
187 fs->regs.cfa_how = CFA_REG_OFFSET;
188 fs->regs.cfa_reg = 4;
189 fs->regs.cfa_offset = new_cfa - (long) context->cfa;
190
191 /* The SVR4 register numbering macros aren't usable in libgcc. */
192 fs->regs.how[0] = REG_SAVED_OFFSET;
193 fs->regs.reg[0].loc.offset = (long)&sf->REG_NAME(eax) - new_cfa;
194 fs->regs.how[3] = REG_SAVED_OFFSET;
195 fs->regs.reg[3].loc.offset = (long)&sf->REG_NAME(ebx) - new_cfa;
196 fs->regs.how[1] = REG_SAVED_OFFSET;
197 fs->regs.reg[1].loc.offset = (long)&sf->REG_NAME(ecx) - new_cfa;
198 fs->regs.how[2] = REG_SAVED_OFFSET;
199 fs->regs.reg[2].loc.offset = (long)&sf->REG_NAME(edx) - new_cfa;
200 fs->regs.how[6] = REG_SAVED_OFFSET;
201 fs->regs.reg[6].loc.offset = (long)&sf->REG_NAME(esi) - new_cfa;
202 fs->regs.how[7] = REG_SAVED_OFFSET;
203 fs->regs.reg[7].loc.offset = (long)&sf->REG_NAME(edi) - new_cfa;
204 fs->regs.how[5] = REG_SAVED_OFFSET;
205 fs->regs.reg[5].loc.offset = (long)&sf->REG_NAME(ebp) - new_cfa;
206 fs->regs.how[8] = REG_SAVED_OFFSET;
207 fs->regs.reg[8].loc.offset = (long)&sf->REG_NAME(eip) - new_cfa;
208 fs->retaddr_column = 8;
209 fs->signal_frame = 1;
210 return _URC_NO_REASON;
211 }
212 #endif /* ifdef __x86_64__ */