1 /* libunwind - a platform-independent unwind library
2 Copyright (C) 2002-2004 Hewlett-Packard Co
3 Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
4
5 Modified for x86_64 by Max Asbock <masbock@us.ibm.com>
6
7 This file is part of libunwind.
8
9 Permission is hereby granted, free of charge, to any person obtaining
10 a copy of this software and associated documentation files (the
11 "Software"), to deal in the Software without restriction, including
12 without limitation the rights to use, copy, modify, merge, publish,
13 distribute, sublicense, and/or sell copies of the Software, and to
14 permit persons to whom the Software is furnished to do so, subject to
15 the following conditions:
16
17 The above copyright notice and this permission notice shall be
18 included in all copies or substantial portions of the Software.
19
20 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
24 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
25 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
26 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
27
28 #include "unwind_i.h"
29 #include <signal.h>
30
31 /* Recognise PLT entries such as:
32 3bdf0: ff 25 e2 49 13 00 jmpq *0x1349e2(%rip)
33 3bdf6: 68 ae 03 00 00 pushq $0x3ae
34 3bdfb: e9 00 c5 ff ff jmpq 38300 <_init+0x18> */
35 static int
is_plt_entry(struct dwarf_cursor * c)36 is_plt_entry (struct dwarf_cursor *c)
37 {
38 unw_word_t w0, w1;
39 unw_accessors_t *a;
40 int ret;
41
42 a = unw_get_accessors (c->as);
43 if ((ret = (*a->access_mem) (c->as, c->ip, &w0, 0, c->as_arg)) < 0
44 || (ret = (*a->access_mem) (c->as, c->ip + 8, &w1, 0, c->as_arg)) < 0)
45 return 0;
46
47 ret = (((w0 & 0xffff) == 0x25ff)
48 && (((w0 >> 48) & 0xff) == 0x68)
49 && (((w1 >> 24) & 0xff) == 0xe9));
50
51 Debug (14, "ip=0x%lx => 0x%016lx 0x%016lx, ret = %d\n", c->ip, w0, w1, ret);
52 return ret;
53 }
54
55 PROTECTED int
unw_step(unw_cursor_t * cursor)56 unw_step (unw_cursor_t *cursor)
57 {
58 struct cursor *c = (struct cursor *) cursor;
59 int ret, i;
60
61 #if CONSERVATIVE_CHECKS
62 int val = c->validate;
63 c->validate = 1;
64 #endif
65
66 Debug (1, "(cursor=%p, ip=0x%016lx, cfa=0x%016lx)\n",
67 c, c->dwarf.ip, c->dwarf.cfa);
68
69 /* Try DWARF-based unwinding... */
70 c->sigcontext_format = X86_64_SCF_NONE;
71 ret = dwarf_step (&c->dwarf);
72
73 #if CONSERVATIVE_CHECKS
74 c->validate = val;
75 #endif
76
77 if (ret < 0 && ret != -UNW_ENOINFO)
78 {
79 Debug (2, "returning %d\n", ret);
80 return ret;
81 }
82
83 if (likely (ret >= 0))
84 {
85 /* x86_64 ABI specifies that end of call-chain is marked with a
86 NULL RBP. */
87 if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
88 {
89 c->dwarf.ip = 0;
90 ret = 0;
91 }
92 }
93 else
94 {
95 /* DWARF failed. There isn't much of a usable frame-chain on x86-64,
96 but we do need to handle two special-cases:
97
98 (i) signal trampoline: Old kernels and older libcs don't
99 export the vDSO needed to get proper unwind info for the
100 trampoline. Recognize that case by looking at the code
101 and filling in things by hand.
102
103 (ii) PLT (shared-library) call-stubs: PLT stubs are invoked
104 via CALLQ. Try this for all non-signal trampoline
105 code. */
106
107 unw_word_t prev_ip = c->dwarf.ip, prev_cfa = c->dwarf.cfa;
108 struct dwarf_loc rbp_loc, rsp_loc, rip_loc;
109
110 /* We could get here because of missing/bad unwind information.
111 Validate all addresses before dereferencing. */
112 c->validate = 1;
113
114 Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret);
115
116 if (unw_is_signal_frame (cursor))
117 {
118 ret = unw_handle_signal_frame(cursor);
119 if (ret < 0)
120 {
121 Debug (2, "returning 0\n");
122 return 0;
123 }
124 }
125 else if (is_plt_entry (&c->dwarf))
126 {
127 /* Like regular frame, CFA = RSP+8, RA = [CFA-8], no regs saved. */
128 Debug (2, "found plt entry\n");
129 c->frame_info.cfa_reg_offset = 8;
130 c->frame_info.cfa_reg_rsp = -1;
131 c->frame_info.frame_type = UNW_X86_64_FRAME_STANDARD;
132 c->dwarf.loc[RIP] = DWARF_LOC (c->dwarf.cfa, 0);
133 c->dwarf.cfa += 8;
134 }
135 else if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
136 {
137 for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
138 c->dwarf.loc[i] = DWARF_NULL_LOC;
139 }
140 else
141 {
142 unw_word_t rbp;
143
144 ret = dwarf_get (&c->dwarf, c->dwarf.loc[RBP], &rbp);
145 if (ret < 0)
146 {
147 Debug (2, "returning %d [RBP=0x%lx]\n", ret,
148 DWARF_GET_LOC (c->dwarf.loc[RBP]));
149 return ret;
150 }
151
152 if (!rbp)
153 {
154 /* Looks like we may have reached the end of the call-chain. */
155 rbp_loc = DWARF_NULL_LOC;
156 rsp_loc = DWARF_NULL_LOC;
157 rip_loc = DWARF_NULL_LOC;
158 }
159 else
160 {
161 unw_word_t rbp1 = 0;
162 rbp_loc = DWARF_LOC(rbp, 0);
163 rsp_loc = DWARF_NULL_LOC;
164 rip_loc = DWARF_LOC (rbp + 8, 0);
165 ret = dwarf_get (&c->dwarf, rbp_loc, &rbp1);
166 Debug (1, "[RBP=0x%lx] = 0x%lx (cfa = 0x%lx) -> 0x%lx\n",
167 (unsigned long) DWARF_GET_LOC (c->dwarf.loc[RBP]),
168 rbp, c->dwarf.cfa, rbp1);
169
170 /* Heuristic to determine incorrect guess. For RBP to be a
171 valid frame it needs to be above current CFA, but don't
172 let it go more than a little. Note that we can't deduce
173 anything about new RBP (rbp1) since it may not be a frame
174 pointer in the frame above. Just check we get the value. */
175 if (ret < 0
176 || rbp <= c->dwarf.cfa
177 || (rbp - c->dwarf.cfa) > 0x4000)
178 {
179 rip_loc = DWARF_NULL_LOC;
180 rbp_loc = DWARF_NULL_LOC;
181 }
182
183 c->frame_info.frame_type = UNW_X86_64_FRAME_GUESSED;
184 c->frame_info.cfa_reg_rsp = 0;
185 c->frame_info.cfa_reg_offset = 16;
186 c->frame_info.rbp_cfa_offset = -16;
187 c->dwarf.cfa += 16;
188 }
189
190 /* Mark all registers unsaved */
191 for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
192 c->dwarf.loc[i] = DWARF_NULL_LOC;
193
194 c->dwarf.loc[RBP] = rbp_loc;
195 c->dwarf.loc[RSP] = rsp_loc;
196 c->dwarf.loc[RIP] = rip_loc;
197 }
198
199 c->dwarf.ret_addr_column = RIP;
200
201 if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
202 {
203 ret = 0;
204 Debug (2, "NULL %%rbp loc, returning %d\n", ret);
205 return ret;
206 }
207 if (!DWARF_IS_NULL_LOC (c->dwarf.loc[RIP]))
208 {
209 ret = dwarf_get (&c->dwarf, c->dwarf.loc[RIP], &c->dwarf.ip);
210 Debug (1, "Frame Chain [RIP=0x%Lx] = 0x%Lx\n",
211 (unsigned long long) DWARF_GET_LOC (c->dwarf.loc[RIP]),
212 (unsigned long long) c->dwarf.ip);
213 if (ret < 0)
214 {
215 Debug (2, "returning %d\n", ret);
216 return ret;
217 }
218 ret = 1;
219 }
220 else
221 c->dwarf.ip = 0;
222
223 if (c->dwarf.ip == prev_ip && c->dwarf.cfa == prev_cfa)
224 return -UNW_EBADFRAME;
225 }
226 /* ANDROID support update. */
227 /* Adjust the pc to the instruction before. */
228 if (c->dwarf.ip)
229 c->dwarf.ip--;
230 /* End of ANDROID update. */
231 Debug (2, "returning %d\n", ret);
232 return ret;
233 }
234