1 /* libunwind - a platform-independent unwind library
2 Copyright (C) 2008 CodeSourcery
3 Copyright (C) 2011-2013 Linaro Limited
4 Copyright (C) 2012 Tommi Rantala <tt.rantala@gmail.com>
5
6 This file is part of libunwind.
7
8 Permission is hereby granted, free of charge, to any person obtaining
9 a copy of this software and associated documentation files (the
10 "Software"), to deal in the Software without restriction, including
11 without limitation the rights to use, copy, modify, merge, publish,
12 distribute, sublicense, and/or sell copies of the Software, and to
13 permit persons to whom the Software is furnished to do so, subject to
14 the following conditions:
15
16 The above copyright notice and this permission notice shall be
17 included in all copies or substantial portions of the Software.
18
19 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
20 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
21 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
22 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
23 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
24 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
25 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
26
27 #include "unwind_i.h"
28 #include "dwarf_i.h"
29
30 PROTECTED int
unw_step(unw_cursor_t * cursor)31 unw_step (unw_cursor_t *cursor)
32 {
33 struct cursor *c = (struct cursor *) cursor;
34 int ret;
35
36 Debug (1, "(cursor=%p, ip=0x%lx, cfa=0x%lx))\n",
37 c, c->dwarf.ip, c->dwarf.cfa);
38
39 /* Check if this is a signal frame. */
40 ret = unw_is_signal_frame (cursor);
41 if (ret < 0)
42 {
43 Debug (2, "returning %d\n", ret);
44 return ret;
45 }
46 if (ret)
47 {
48 ret = unw_handle_signal_frame (cursor);
49 Debug (2, "returning %d\n", ret);
50 return ret;
51 }
52
53 ret = dwarf_step (&c->dwarf);
54 Debug(1, "dwarf_step()=%d\n", ret);
55
56 if (unlikely (ret == -UNW_ESTOPUNWIND))
57 {
58 Debug (2, "returning %d\n", ret);
59 return ret;
60 }
61
62 if (ret < 0 && ret != -UNW_ENOINFO)
63 {
64 Debug (2, "returning %d\n", 0);
65 return 0;
66 }
67
68 if (ret >= 0)
69 {
70 ret = (c->dwarf.ip == 0) ? 0 : 1;
71 }
72 else // ret == -UNW_ENOINFO
73 {
74 // If there's no unwind info fall back to a heuristic.
75 // TODO: Make configurable? unw_step_etc?
76 // Note: This is copied from x86_64.
77 // TODO: arm64 has a canonical frame pointer: r29. But it's not clear
78 // yet whether the heuristics that x86_64/Gstep.c employees can just be
79 // carried over.
80
81 unw_word_t prev_ip = c->dwarf.ip, prev_cfa = c->dwarf.cfa;
82 struct dwarf_loc sp_loc, pc_loc;
83
84 // We could get here because of missing/bad unwind information.
85 // Validate all addresses from now on before dereferencing.
86 c->validate = 1;
87
88 Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret);
89
90 if (DWARF_IS_NULL_LOC (c->dwarf.loc[UNW_AARCH64_SP]))
91 {
92 for (int i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
93 c->dwarf.loc[i] = DWARF_NULL_LOC;
94 }
95 else
96 {
97 unw_word_t sp;
98
99 ret = dwarf_get (&c->dwarf, c->dwarf.loc[UNW_AARCH64_SP], &sp);
100 if (ret < 0)
101 {
102 Debug (2, "returning %d [SP=0x%lx]\n", ret,
103 DWARF_GET_LOC (c->dwarf.loc[UNW_AARCH64_SP]));
104 return ret;
105 }
106
107 if (!sp)
108 {
109 /* Looks like we may have reached the end of the call-chain. */
110 sp_loc = DWARF_NULL_LOC;
111 pc_loc = DWARF_NULL_LOC;
112 }
113 else
114 {
115 unw_word_t sp1 = 0;
116 sp_loc = DWARF_LOC (sp, 0);
117 pc_loc = DWARF_LOC (sp + 8, 0);
118 ret = dwarf_get (&c->dwarf, sp_loc, &sp1);
119 Debug (1, "[SP=0x%lx] = 0x%lx (cfa = 0x%lx) -> 0x%lx\n",
120 (unsigned long) DWARF_GET_LOC (c->dwarf.loc[UNW_AARCH64_SP]),
121 sp, c->dwarf.cfa, sp1);
122
123 #if 0 // TODO: wip
124 /* Heuristic to determine incorrect guess. For SP to be a
125 valid frame it needs to be above current CFA, but don't
126 let it go more than a little. Note that we can't deduce
127 anything about new SP (sp1) since it may not be a frame
128 pointer in the frame above. Just check we get the value. */
129 if (ret < 0
130 || rbp < c->dwarf.cfa
131 || (rbp - c->dwarf.cfa) > 0x4000)
132 {
133 pc_loc = DWARF_NULL_LOC;
134 sp_loc = DWARF_NULL_LOC;
135 }
136 #endif
137
138 c->frame_info.frame_type = UNW_AARCH64_FRAME_GUESSED;
139 c->frame_info.cfa_reg_sp = 0;
140 c->frame_info.cfa_reg_offset = 16;
141 c->frame_info.sp_cfa_offset = -16;
142 c->dwarf.cfa += 16;
143 }
144
145 /* Mark all registers unsaved */
146 for (int i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
147 c->dwarf.loc[i] = DWARF_NULL_LOC;
148
149 c->dwarf.loc[UNW_AARCH64_SP] = sp_loc;
150 c->dwarf.loc[UNW_AARCH64_PC] = pc_loc;
151 c->dwarf.use_prev_instr = 1;
152 }
153
154 c->dwarf.ret_addr_column = UNW_AARCH64_PC;
155
156 if (DWARF_IS_NULL_LOC (c->dwarf.loc[UNW_AARCH64_SP]))
157 {
158 ret = 0;
159 Debug (2, "NULL %%sp loc, returning %d\n", ret);
160 return ret;
161 }
162 if (!DWARF_IS_NULL_LOC (c->dwarf.loc[UNW_AARCH64_PC]))
163 {
164 ret = dwarf_get (&c->dwarf, c->dwarf.loc[UNW_AARCH64_PC], &c->dwarf.ip);
165 Debug (1, "Frame Chain [PC=0x%Lx] = 0x%Lx\n",
166 (unsigned long long) DWARF_GET_LOC (c->dwarf.loc[UNW_AARCH64_PC]),
167 (unsigned long long) c->dwarf.ip);
168 if (ret < 0)
169 {
170 Debug (2, "returning %d\n", ret);
171 return ret;
172 }
173 ret = 1;
174 }
175 else
176 {
177 c->dwarf.ip = 0;
178 ret = 0;
179 }
180
181 if (c->dwarf.ip == prev_ip && c->dwarf.cfa == prev_cfa)
182 {
183 ret = -UNW_EBADFRAME;
184 Debug (2, "returning %d\n", ret);
185 return ret;
186 }
187 }
188
189 Debug (2, "returning %d\n", ret);
190 return ret;
191 }
192