1 /* libunwind - a platform-independent unwind library
2 Copyright (C) 2003-2004 Hewlett-Packard Co
3 Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
4
5 This file is part of libunwind.
6
7 Permission is hereby granted, free of charge, to any person obtaining
8 a copy of this software and associated documentation files (the
9 "Software"), to deal in the Software without restriction, including
10 without limitation the rights to use, copy, modify, merge, publish,
11 distribute, sublicense, and/or sell copies of the Software, and to
12 permit persons to whom the Software is furnished to do so, subject to
13 the following conditions:
14
15 The above copyright notice and this permission notice shall be
16 included in all copies or substantial portions of the Software.
17
18 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
19 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
21 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
22 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
23 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
24 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
25
26 #include <fcntl.h>
27 #include <string.h>
28 #include <unistd.h>
29
30 #include <sys/mman.h>
31
32 #include "libunwind_i.h"
33 #include "dwarf-eh.h"
34 #include "dwarf_i.h"
35
36 #define to_unw_word(p) ((unw_word_t) (uintptr_t) (p))
37
38 int
dwarf_find_unwind_table(struct elf_dyn_info * edi,unw_addr_space_t as,char * path,unw_word_t segbase,unw_word_t mapoff,unw_word_t ip)39 dwarf_find_unwind_table (struct elf_dyn_info *edi, unw_addr_space_t as,
40 char *path, unw_word_t segbase, unw_word_t mapoff,
41 unw_word_t ip)
42 {
43 Elf_W(Phdr) *phdr, *ptxt = NULL, *peh_hdr = NULL, *pdyn = NULL;
44 unw_word_t addr, eh_frame_start, fde_count, load_base;
45 unw_word_t max_load_addr = 0;
46 unw_word_t start_ip = to_unw_word (-1);
47 unw_word_t end_ip = 0;
48 struct dwarf_eh_frame_hdr *hdr;
49 unw_proc_info_t pi;
50 unw_accessors_t *a;
51 Elf_W(Ehdr) *ehdr;
52 #if UNW_TARGET_ARM
53 const Elf_W(Phdr) *parm_exidx = NULL;
54 #endif
55 int i, ret, found = 0;
56
57 /* XXX: Much of this code is Linux/LSB-specific. */
58
59 if (!elf_w(valid_object) (&edi->ei))
60 return -UNW_ENOINFO;
61
62 ehdr = edi->ei.image;
63 phdr = (Elf_W(Phdr) *) ((char *) edi->ei.image + ehdr->e_phoff);
64
65 for (i = 0; i < ehdr->e_phnum; ++i)
66 {
67 switch (phdr[i].p_type)
68 {
69 case PT_LOAD:
70 if (phdr[i].p_vaddr < start_ip)
71 start_ip = phdr[i].p_vaddr;
72
73 if (phdr[i].p_vaddr + phdr[i].p_memsz > end_ip)
74 end_ip = phdr[i].p_vaddr + phdr[i].p_memsz;
75
76 if (phdr[i].p_offset == mapoff)
77 ptxt = phdr + i;
78 if ((uintptr_t) edi->ei.image + phdr->p_filesz > max_load_addr)
79 max_load_addr = (uintptr_t) edi->ei.image + phdr->p_filesz;
80 break;
81
82 case PT_GNU_EH_FRAME:
83 #if defined __sun
84 case PT_SUNW_UNWIND:
85 #endif
86 peh_hdr = phdr + i;
87 break;
88
89 case PT_DYNAMIC:
90 pdyn = phdr + i;
91 break;
92
93 #if UNW_TARGET_ARM
94 case PT_ARM_EXIDX:
95 parm_exidx = phdr + i;
96 break;
97 #endif
98
99 default:
100 break;
101 }
102 }
103
104 if (!ptxt)
105 return 0;
106
107 load_base = segbase - ptxt->p_vaddr;
108 start_ip += load_base;
109 end_ip += load_base;
110
111 if (peh_hdr)
112 {
113 if (pdyn)
114 {
115 /* For dynamicly linked executables and shared libraries,
116 DT_PLTGOT is the value that data-relative addresses are
117 relative to for that object. We call this the "gp". */
118 Elf_W(Dyn) *dyn = (Elf_W(Dyn) *)(pdyn->p_offset
119 + (char *) edi->ei.image);
120 for (; dyn->d_tag != DT_NULL; ++dyn)
121 if (dyn->d_tag == DT_PLTGOT)
122 {
123 /* Assume that _DYNAMIC is writable and GLIBC has
124 relocated it (true for x86 at least). */
125 edi->di_cache.gp = dyn->d_un.d_ptr;
126 break;
127 }
128 }
129 else
130 /* Otherwise this is a static executable with no _DYNAMIC. Assume
131 that data-relative addresses are relative to 0, i.e.,
132 absolute. */
133 edi->di_cache.gp = 0;
134
135 hdr = (struct dwarf_eh_frame_hdr *) (peh_hdr->p_offset
136 + (char *) edi->ei.image);
137 if (hdr->version != DW_EH_VERSION)
138 {
139 Debug (1, "table `%s' has unexpected version %d\n",
140 path, hdr->version);
141 return -UNW_ENOINFO;
142 }
143
144 a = unw_get_accessors_int (unw_local_addr_space);
145 addr = to_unw_word (&hdr->eh_frame);
146
147 /* Fill in a dummy proc_info structure. We just need to fill in
148 enough to ensure that dwarf_read_encoded_pointer() can do it's
149 job. Since we don't have a procedure-context at this point, all
150 we have to do is fill in the global-pointer. */
151 memset (&pi, 0, sizeof (pi));
152 pi.gp = edi->di_cache.gp;
153
154 /* (Optionally) read eh_frame_ptr: */
155 if ((ret = dwarf_read_encoded_pointer (unw_local_addr_space, a,
156 &addr, hdr->eh_frame_ptr_enc, &pi,
157 &eh_frame_start, NULL)) < 0)
158 return -UNW_ENOINFO;
159
160 /* (Optionally) read fde_count: */
161 if ((ret = dwarf_read_encoded_pointer (unw_local_addr_space, a,
162 &addr, hdr->fde_count_enc, &pi,
163 &fde_count, NULL)) < 0)
164 return -UNW_ENOINFO;
165
166 if (hdr->table_enc != (DW_EH_PE_datarel | DW_EH_PE_sdata4))
167 {
168 #if 1
169 abort ();
170 #else
171 unw_word_t eh_frame_end;
172
173 /* If there is no search table or it has an unsupported
174 encoding, fall back on linear search. */
175 if (hdr->table_enc == DW_EH_PE_omit)
176 Debug (4, "EH lacks search table; doing linear search\n");
177 else
178 Debug (4, "EH table has encoding 0x%x; doing linear search\n",
179 hdr->table_enc);
180
181 eh_frame_end = max_load_addr; /* XXX can we do better? */
182
183 if (hdr->fde_count_enc == DW_EH_PE_omit)
184 fde_count = ~0UL;
185 if (hdr->eh_frame_ptr_enc == DW_EH_PE_omit)
186 abort ();
187
188 return linear_search (unw_local_addr_space, ip,
189 eh_frame_start, eh_frame_end, fde_count,
190 pi, need_unwind_info, NULL);
191 #endif
192 }
193
194 edi->di_cache.start_ip = start_ip;
195 edi->di_cache.end_ip = end_ip;
196 edi->di_cache.load_offset = 0;
197 edi->di_cache.format = UNW_INFO_FORMAT_REMOTE_TABLE;
198 edi->di_cache.u.rti.name_ptr = 0;
199 /* two 32-bit values (ip_offset/fde_offset) per table-entry: */
200 edi->di_cache.u.rti.table_len = (fde_count * 8) / sizeof (unw_word_t);
201 edi->di_cache.u.rti.table_data = ((load_base + peh_hdr->p_vaddr)
202 + (addr - to_unw_word (edi->ei.image)
203 - peh_hdr->p_offset));
204
205 /* For the binary-search table in the eh_frame_hdr, data-relative
206 means relative to the start of that section... */
207 edi->di_cache.u.rti.segbase = ((load_base + peh_hdr->p_vaddr)
208 + (to_unw_word (hdr) -
209 to_unw_word (edi->ei.image)
210 - peh_hdr->p_offset));
211 found = 1;
212 }
213
214 #if UNW_TARGET_ARM
215 if (parm_exidx)
216 {
217 edi->di_arm.format = UNW_INFO_FORMAT_ARM_EXIDX;
218 edi->di_arm.start_ip = start_ip;
219 edi->di_arm.end_ip = end_ip;
220 edi->di_arm.u.rti.name_ptr = to_unw_word (path);
221 edi->di_arm.u.rti.table_data = load_base + parm_exidx->p_vaddr;
222 edi->di_arm.u.rti.table_len = parm_exidx->p_memsz;
223 found = 1;
224 }
225 #endif
226
227 #ifdef CONFIG_DEBUG_FRAME
228 /* Try .debug_frame. */
229 found = dwarf_find_debug_frame (found, &edi->di_debug, ip, load_base, path,
230 start_ip, end_ip);
231 #endif
232
233 return found;
234 }
235