1 /*
2 * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
16 */
17
18 #include <stdlib.h>
19 #include <string.h>
20
21 #include "orc.h"
22 #include "check.h"
23 #include "warn.h"
24
create_orc(struct objtool_file * file)25 int create_orc(struct objtool_file *file)
26 {
27 struct instruction *insn;
28
29 for_each_insn(file, insn) {
30 struct orc_entry *orc = &insn->orc;
31 struct cfi_reg *cfa = &insn->state.cfa;
32 struct cfi_reg *bp = &insn->state.regs[CFI_BP];
33
34 orc->end = insn->state.end;
35
36 if (cfa->base == CFI_UNDEFINED) {
37 orc->sp_reg = ORC_REG_UNDEFINED;
38 continue;
39 }
40
41 switch (cfa->base) {
42 case CFI_SP:
43 orc->sp_reg = ORC_REG_SP;
44 break;
45 case CFI_SP_INDIRECT:
46 orc->sp_reg = ORC_REG_SP_INDIRECT;
47 break;
48 case CFI_BP:
49 orc->sp_reg = ORC_REG_BP;
50 break;
51 case CFI_BP_INDIRECT:
52 orc->sp_reg = ORC_REG_BP_INDIRECT;
53 break;
54 case CFI_R10:
55 orc->sp_reg = ORC_REG_R10;
56 break;
57 case CFI_R13:
58 orc->sp_reg = ORC_REG_R13;
59 break;
60 case CFI_DI:
61 orc->sp_reg = ORC_REG_DI;
62 break;
63 case CFI_DX:
64 orc->sp_reg = ORC_REG_DX;
65 break;
66 default:
67 WARN_FUNC("unknown CFA base reg %d",
68 insn->sec, insn->offset, cfa->base);
69 return -1;
70 }
71
72 switch(bp->base) {
73 case CFI_UNDEFINED:
74 orc->bp_reg = ORC_REG_UNDEFINED;
75 break;
76 case CFI_CFA:
77 orc->bp_reg = ORC_REG_PREV_SP;
78 break;
79 case CFI_BP:
80 orc->bp_reg = ORC_REG_BP;
81 break;
82 default:
83 WARN_FUNC("unknown BP base reg %d",
84 insn->sec, insn->offset, bp->base);
85 return -1;
86 }
87
88 orc->sp_offset = cfa->offset;
89 orc->bp_offset = bp->offset;
90 orc->type = insn->state.type;
91 }
92
93 return 0;
94 }
95
create_orc_entry(struct section * u_sec,struct section * ip_relasec,unsigned int idx,struct section * insn_sec,unsigned long insn_off,struct orc_entry * o)96 static int create_orc_entry(struct section *u_sec, struct section *ip_relasec,
97 unsigned int idx, struct section *insn_sec,
98 unsigned long insn_off, struct orc_entry *o)
99 {
100 struct orc_entry *orc;
101 struct rela *rela;
102
103 /* populate ORC data */
104 orc = (struct orc_entry *)u_sec->data->d_buf + idx;
105 memcpy(orc, o, sizeof(*orc));
106
107 /* populate rela for ip */
108 rela = malloc(sizeof(*rela));
109 if (!rela) {
110 perror("malloc");
111 return -1;
112 }
113 memset(rela, 0, sizeof(*rela));
114
115 if (insn_sec->sym) {
116 rela->sym = insn_sec->sym;
117 rela->addend = insn_off;
118 } else {
119 /*
120 * The Clang assembler doesn't produce section symbols, so we
121 * have to reference the function symbol instead:
122 */
123 rela->sym = find_symbol_containing(insn_sec, insn_off);
124 if (!rela->sym) {
125 /*
126 * Hack alert. This happens when we need to reference
127 * the NOP pad insn immediately after the function.
128 */
129 rela->sym = find_symbol_containing(insn_sec,
130 insn_off - 1);
131 }
132 if (!rela->sym) {
133 WARN("missing symbol for insn at offset 0x%lx\n",
134 insn_off);
135 return -1;
136 }
137
138 rela->addend = insn_off - rela->sym->offset;
139 }
140
141 rela->type = R_X86_64_PC32;
142 rela->offset = idx * sizeof(int);
143
144 list_add_tail(&rela->list, &ip_relasec->rela_list);
145 hash_add(ip_relasec->rela_hash, &rela->hash, rela->offset);
146
147 return 0;
148 }
149
create_orc_sections(struct objtool_file * file)150 int create_orc_sections(struct objtool_file *file)
151 {
152 struct instruction *insn, *prev_insn;
153 struct section *sec, *u_sec, *ip_relasec;
154 unsigned int idx;
155
156 struct orc_entry empty = {
157 .sp_reg = ORC_REG_UNDEFINED,
158 .bp_reg = ORC_REG_UNDEFINED,
159 .type = ORC_TYPE_CALL,
160 };
161
162 sec = find_section_by_name(file->elf, ".orc_unwind");
163 if (sec) {
164 WARN("file already has .orc_unwind section, skipping");
165 return -1;
166 }
167
168 /* count the number of needed orcs */
169 idx = 0;
170 for_each_sec(file, sec) {
171 if (!sec->text)
172 continue;
173
174 prev_insn = NULL;
175 sec_for_each_insn(file, sec, insn) {
176 if (!prev_insn ||
177 memcmp(&insn->orc, &prev_insn->orc,
178 sizeof(struct orc_entry))) {
179 idx++;
180 }
181 prev_insn = insn;
182 }
183
184 /* section terminator */
185 if (prev_insn)
186 idx++;
187 }
188 if (!idx)
189 return -1;
190
191
192 /* create .orc_unwind_ip and .rela.orc_unwind_ip sections */
193 sec = elf_create_section(file->elf, ".orc_unwind_ip", sizeof(int), idx);
194 if (!sec)
195 return -1;
196
197 ip_relasec = elf_create_rela_section(file->elf, sec);
198 if (!ip_relasec)
199 return -1;
200
201 /* create .orc_unwind section */
202 u_sec = elf_create_section(file->elf, ".orc_unwind",
203 sizeof(struct orc_entry), idx);
204
205 /* populate sections */
206 idx = 0;
207 for_each_sec(file, sec) {
208 if (!sec->text)
209 continue;
210
211 prev_insn = NULL;
212 sec_for_each_insn(file, sec, insn) {
213 if (!prev_insn || memcmp(&insn->orc, &prev_insn->orc,
214 sizeof(struct orc_entry))) {
215
216 if (create_orc_entry(u_sec, ip_relasec, idx,
217 insn->sec, insn->offset,
218 &insn->orc))
219 return -1;
220
221 idx++;
222 }
223 prev_insn = insn;
224 }
225
226 /* section terminator */
227 if (prev_insn) {
228 if (create_orc_entry(u_sec, ip_relasec, idx,
229 prev_insn->sec,
230 prev_insn->offset + prev_insn->len,
231 &empty))
232 return -1;
233
234 idx++;
235 }
236 }
237
238 if (elf_rebuild_rela_section(ip_relasec))
239 return -1;
240
241 return 0;
242 }
243