1 | /* Copyright (C) 2001-2022 Free Software Foundation, Inc. |
2 | |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | /* Locate the FDE entry for a given address, using PT_GNU_EH_FRAME ELF |
20 | segment and dl_iterate_phdr to avoid register/deregister calls at |
21 | DSO load/unload. */ |
22 | |
23 | #ifdef _LIBC |
24 | # include <shlib-compat.h> |
25 | #endif |
26 | |
27 | #if !defined _LIBC || SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_2_5) |
28 | |
29 | #include <link.h> |
30 | #include <stddef.h> |
31 | |
32 | #define _Unwind_Find_FDE _Unwind_Find_registered_FDE |
33 | |
34 | #include <unwind-dw2-fde.c> |
35 | |
36 | #undef _Unwind_Find_FDE |
37 | |
38 | extern fde * _Unwind_Find_registered_FDE (void *pc, |
39 | struct dwarf_eh_bases *bases); |
40 | extern fde * _Unwind_Find_FDE (void *, struct dwarf_eh_bases *); |
41 | |
42 | struct unw_eh_callback_data |
43 | { |
44 | _Unwind_Ptr pc; |
45 | void *tbase; |
46 | void *dbase; |
47 | void *func; |
48 | fde *ret; |
49 | }; |
50 | |
51 | struct unw_eh_frame_hdr |
52 | { |
53 | unsigned char version; |
54 | unsigned char eh_frame_ptr_enc; |
55 | unsigned char fde_count_enc; |
56 | unsigned char table_enc; |
57 | }; |
58 | |
59 | /* Like base_of_encoded_value, but take the base from a struct object |
60 | instead of an _Unwind_Context. */ |
61 | |
62 | static _Unwind_Ptr |
63 | base_from_cb_data (unsigned char encoding, struct unw_eh_callback_data *data) |
64 | { |
65 | if (encoding == DW_EH_PE_omit) |
66 | return 0; |
67 | |
68 | switch (encoding & 0x70) |
69 | { |
70 | case DW_EH_PE_absptr: |
71 | case DW_EH_PE_pcrel: |
72 | case DW_EH_PE_aligned: |
73 | return 0; |
74 | |
75 | case DW_EH_PE_textrel: |
76 | return (_Unwind_Ptr) data->tbase; |
77 | case DW_EH_PE_datarel: |
78 | return (_Unwind_Ptr) data->dbase; |
79 | } |
80 | abort (); |
81 | } |
82 | |
83 | static int |
84 | _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr) |
85 | { |
86 | struct unw_eh_callback_data *data = (struct unw_eh_callback_data *) ptr; |
87 | const ElfW(Phdr) *phdr, *p_eh_frame_hdr; |
88 | const ElfW(Phdr) *p_dynamic __attribute__ ((unused)); |
89 | long n, match; |
90 | _Unwind_Ptr load_base; |
91 | const unsigned char *p; |
92 | const struct unw_eh_frame_hdr *hdr; |
93 | _Unwind_Ptr eh_frame; |
94 | struct object ob; |
95 | |
96 | /* Make sure struct dl_phdr_info is at least as big as we need. */ |
97 | if (size < offsetof (struct dl_phdr_info, dlpi_phnum) |
98 | + sizeof (info->dlpi_phnum)) |
99 | return -1; |
100 | |
101 | match = 0; |
102 | phdr = info->dlpi_phdr; |
103 | load_base = info->dlpi_addr; |
104 | p_eh_frame_hdr = NULL; |
105 | p_dynamic = NULL; |
106 | |
107 | /* See if PC falls into one of the loaded segments. Find the eh_frame |
108 | segment at the same time. */ |
109 | for (n = info->dlpi_phnum; --n >= 0; phdr++) |
110 | { |
111 | if (phdr->p_type == PT_LOAD) |
112 | { |
113 | _Unwind_Ptr vaddr = phdr->p_vaddr + load_base; |
114 | if (data->pc >= vaddr && data->pc < vaddr + phdr->p_memsz) |
115 | match = 1; |
116 | } |
117 | else if (phdr->p_type == PT_GNU_EH_FRAME) |
118 | p_eh_frame_hdr = phdr; |
119 | else if (phdr->p_type == PT_DYNAMIC) |
120 | p_dynamic = phdr; |
121 | } |
122 | if (!match || !p_eh_frame_hdr) |
123 | return 0; |
124 | |
125 | /* Read .eh_frame_hdr header. */ |
126 | hdr = (const struct unw_eh_frame_hdr *) |
127 | (p_eh_frame_hdr->p_vaddr + load_base); |
128 | if (hdr->version != 1) |
129 | return 1; |
130 | |
131 | #ifdef CRT_GET_RFIB_DATA |
132 | # ifdef __i386__ |
133 | data->dbase = NULL; |
134 | if (p_dynamic) |
135 | { |
136 | /* For dynamicly linked executables and shared libraries, |
137 | DT_PLTGOT is the gp value for that object. */ |
138 | ElfW(Dyn) *dyn = (ElfW(Dyn) *)(p_dynamic->p_vaddr + load_base); |
139 | for (; dyn->d_tag != DT_NULL ; dyn++) |
140 | if (dyn->d_tag == DT_PLTGOT) |
141 | { |
142 | /* On IA-32, _DYNAMIC is writable and GLIBC has relocated it. */ |
143 | data->dbase = (void *) dyn->d_un.d_ptr; |
144 | break; |
145 | } |
146 | } |
147 | # else |
148 | # error What is DW_EH_PE_datarel base on this platform? |
149 | # endif |
150 | #endif |
151 | #ifdef CRT_GET_RFIB_TEXT |
152 | # error What is DW_EH_PE_textrel base on this platform? |
153 | #endif |
154 | |
155 | p = read_encoded_value_with_base (encoding: hdr->eh_frame_ptr_enc, |
156 | base: base_from_cb_data (encoding: hdr->eh_frame_ptr_enc, |
157 | data), |
158 | p: (const unsigned char *) (hdr + 1), |
159 | val: &eh_frame); |
160 | |
161 | /* We require here specific table encoding to speed things up. |
162 | Also, DW_EH_PE_datarel here means using PT_GNU_EH_FRAME start |
163 | as base, not the processor specific DW_EH_PE_datarel. */ |
164 | if (hdr->fde_count_enc != DW_EH_PE_omit |
165 | && hdr->table_enc == (DW_EH_PE_datarel | DW_EH_PE_sdata4)) |
166 | { |
167 | _Unwind_Ptr fde_count; |
168 | |
169 | p = read_encoded_value_with_base (encoding: hdr->fde_count_enc, |
170 | base: base_from_cb_data (encoding: hdr->fde_count_enc, |
171 | data), |
172 | p, val: &fde_count); |
173 | /* Shouldn't happen. */ |
174 | if (fde_count == 0) |
175 | return 1; |
176 | if ((((_Unwind_Ptr) p) & 3) == 0) |
177 | { |
178 | struct fde_table { |
179 | signed initial_loc __attribute__ ((mode (SI))); |
180 | signed fde __attribute__ ((mode (SI))); |
181 | }; |
182 | const struct fde_table *table = (const struct fde_table *) p; |
183 | size_t lo, hi, mid; |
184 | _Unwind_Ptr data_base = (_Unwind_Ptr) hdr; |
185 | fde *f; |
186 | unsigned int f_enc, f_enc_size; |
187 | _Unwind_Ptr range; |
188 | |
189 | mid = fde_count - 1; |
190 | if (data->pc < table[0].initial_loc + data_base) |
191 | return 1; |
192 | else if (data->pc < table[mid].initial_loc + data_base) |
193 | { |
194 | lo = 0; |
195 | hi = mid; |
196 | |
197 | while (lo < hi) |
198 | { |
199 | mid = (lo + hi) / 2; |
200 | if (data->pc < table[mid].initial_loc + data_base) |
201 | hi = mid; |
202 | else if (data->pc >= table[mid + 1].initial_loc + data_base) |
203 | lo = mid + 1; |
204 | else |
205 | break; |
206 | } |
207 | |
208 | if (lo >= hi) |
209 | __gxx_abort (); |
210 | } |
211 | |
212 | f = (fde *) (table[mid].fde + data_base); |
213 | f_enc = get_fde_encoding (f); |
214 | f_enc_size = size_of_encoded_value (encoding: f_enc); |
215 | read_encoded_value_with_base (encoding: f_enc & 0x0f, base: 0, |
216 | p: &f->pc_begin[f_enc_size], val: &range); |
217 | if (data->pc < table[mid].initial_loc + data_base + range) |
218 | data->ret = f; |
219 | data->func = (void *) (table[mid].initial_loc + data_base); |
220 | return 1; |
221 | } |
222 | } |
223 | |
224 | /* We have no sorted search table, so need to go the slow way. |
225 | As soon as GLIBC will provide API so to notify that a library has been |
226 | removed, we could cache this (and thus use search_object). */ |
227 | ob.pc_begin = NULL; |
228 | ob.tbase = data->tbase; |
229 | ob.dbase = data->dbase; |
230 | ob.u.single = (fde *) eh_frame; |
231 | ob.s.i = 0; |
232 | ob.s.b.mixed_encoding = 1; /* Need to assume worst case. */ |
233 | data->ret = linear_search_fdes (ob: &ob, this_fde: (fde *) eh_frame, pc: (void *) data->pc); |
234 | if (data->ret != NULL) |
235 | { |
236 | unsigned int encoding = get_fde_encoding (f: data->ret); |
237 | _Unwind_Ptr func; |
238 | read_encoded_value_with_base (encoding, |
239 | base: base_from_cb_data (encoding, data), |
240 | p: data->ret->pc_begin, val: &func); |
241 | data->func = (void *) func; |
242 | } |
243 | return 1; |
244 | } |
245 | |
246 | # ifdef _LIBC |
247 | # define dl_iterate_phdr __dl_iterate_phdr |
248 | # endif |
249 | |
250 | fde * |
251 | _Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases) |
252 | { |
253 | struct unw_eh_callback_data data; |
254 | fde *ret; |
255 | |
256 | ret = _Unwind_Find_registered_FDE (pc, bases); |
257 | if (ret != NULL) |
258 | return ret; |
259 | |
260 | data.pc = (_Unwind_Ptr) pc; |
261 | data.tbase = NULL; |
262 | data.dbase = NULL; |
263 | data.func = NULL; |
264 | data.ret = NULL; |
265 | |
266 | if (dl_iterate_phdr (_Unwind_IteratePhdrCallback, &data) < 0) |
267 | return NULL; |
268 | |
269 | if (data.ret) |
270 | { |
271 | bases->tbase = data.tbase; |
272 | bases->dbase = data.dbase; |
273 | bases->func = data.func; |
274 | } |
275 | return data.ret; |
276 | } |
277 | |
278 | #endif |
279 | |