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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
4 */
5
6#include <stdlib.h>
7#include <string.h>
8
9#include <linux/objtool.h>
10#include <asm/orc_types.h>
11
12#include <objtool/check.h>
13#include <objtool/warn.h>
14#include <objtool/endianness.h>
15
16static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi)
17{
18 struct instruction *insn = container_of(cfi, struct instruction, cfi);
19 struct cfi_reg *bp = &cfi->regs[CFI_BP];
20
21 memset(orc, 0, sizeof(*orc));
22
23 orc->end = cfi->end;
24
25 if (cfi->cfa.base == CFI_UNDEFINED) {
26 orc->sp_reg = ORC_REG_UNDEFINED;
27 return 0;
28 }
29
30 switch (cfi->cfa.base) {
31 case CFI_SP:
32 orc->sp_reg = ORC_REG_SP;
33 break;
34 case CFI_SP_INDIRECT:
35 orc->sp_reg = ORC_REG_SP_INDIRECT;
36 break;
37 case CFI_BP:
38 orc->sp_reg = ORC_REG_BP;
39 break;
40 case CFI_BP_INDIRECT:
41 orc->sp_reg = ORC_REG_BP_INDIRECT;
42 break;
43 case CFI_R10:
44 orc->sp_reg = ORC_REG_R10;
45 break;
46 case CFI_R13:
47 orc->sp_reg = ORC_REG_R13;
48 break;
49 case CFI_DI:
50 orc->sp_reg = ORC_REG_DI;
51 break;
52 case CFI_DX:
53 orc->sp_reg = ORC_REG_DX;
54 break;
55 default:
56 WARN_FUNC("unknown CFA base reg %d",
57 insn->sec, insn->offset, cfi->cfa.base);
58 return -1;
59 }
60
61 switch (bp->base) {
62 case CFI_UNDEFINED:
63 orc->bp_reg = ORC_REG_UNDEFINED;
64 break;
65 case CFI_CFA:
66 orc->bp_reg = ORC_REG_PREV_SP;
67 break;
68 case CFI_BP:
69 orc->bp_reg = ORC_REG_BP;
70 break;
71 default:
72 WARN_FUNC("unknown BP base reg %d",
73 insn->sec, insn->offset, bp->base);
74 return -1;
75 }
76
77 orc->sp_offset = cfi->cfa.offset;
78 orc->bp_offset = bp->offset;
79 orc->type = cfi->type;
80
81 return 0;
82}
83
84static int write_orc_entry(struct elf *elf, struct section *orc_sec,
85 struct section *ip_rsec, unsigned int idx,
86 struct section *insn_sec, unsigned long insn_off,
87 struct orc_entry *o)
88{
89 struct orc_entry *orc;
90 struct reloc *reloc;
91
92 /* populate ORC data */
93 orc = (struct orc_entry *)orc_sec->data->d_buf + idx;
94 memcpy(orc, o, sizeof(*orc));
95 orc->sp_offset = bswap_if_needed(orc->sp_offset);
96 orc->bp_offset = bswap_if_needed(orc->bp_offset);
97
98 /* populate reloc for ip */
99 reloc = malloc(sizeof(*reloc));
100 if (!reloc) {
101 perror("malloc");
102 return -1;
103 }
104 memset(reloc, 0, sizeof(*reloc));
105
106 insn_to_reloc_sym_addend(insn_sec, insn_off, reloc);
107 if (!reloc->sym) {
108 WARN("missing symbol for insn at offset 0x%lx",
109 insn_off);
110 return -1;
111 }
112
113 reloc->type = R_X86_64_PC32;
114 reloc->offset = idx * sizeof(int);
115 reloc->sec = ip_rsec;
116
117 elf_add_reloc(elf, reloc);
118
119 return 0;
120}
121
122struct orc_list_entry {
123 struct list_head list;
124 struct orc_entry orc;
125 struct section *insn_sec;
126 unsigned long insn_off;
127};
128
129static int orc_list_add(struct list_head *orc_list, struct orc_entry *orc,
130 struct section *sec, unsigned long offset)
131{
132 struct orc_list_entry *entry = malloc(sizeof(*entry));
133
134 if (!entry) {
135 WARN("malloc failed");
136 return -1;
137 }
138
139 entry->orc = *orc;
140 entry->insn_sec = sec;
141 entry->insn_off = offset;
142
143 list_add_tail(&entry->list, orc_list);
144 return 0;
145}
146
147static unsigned long alt_group_len(struct alt_group *alt_group)
148{
149 return alt_group->last_insn->offset +
150 alt_group->last_insn->len -
151 alt_group->first_insn->offset;
152}
153
154int orc_create(struct objtool_file *file)
155{
156 struct section *sec, *ip_rsec, *orc_sec;
157 unsigned int nr = 0, idx = 0;
158 struct orc_list_entry *entry;
159 struct list_head orc_list;
160
161 struct orc_entry null = {
162 .sp_reg = ORC_REG_UNDEFINED,
163 .bp_reg = ORC_REG_UNDEFINED,
164 .type = UNWIND_HINT_TYPE_CALL,
165 };
166
167 /* Build a deduplicated list of ORC entries: */
168 INIT_LIST_HEAD(&orc_list);
169 for_each_sec(file, sec) {
170 struct orc_entry orc, prev_orc = {0};
171 struct instruction *insn;
172 bool empty = true;
173
174 if (!sec->text)
175 continue;
176
177 sec_for_each_insn(file, sec, insn) {
178 struct alt_group *alt_group = insn->alt_group;
179 int i;
180
181 if (!alt_group) {
182 if (init_orc_entry(&orc, &insn->cfi))
183 return -1;
184 if (!memcmp(&prev_orc, &orc, sizeof(orc)))
185 continue;
186 if (orc_list_add(&orc_list, &orc, sec,
187 insn->offset))
188 return -1;
189 nr++;
190 prev_orc = orc;
191 empty = false;
192 continue;
193 }
194
195 /*
196 * Alternatives can have different stack layout
197 * possibilities (but they shouldn't conflict).
198 * Instead of traversing the instructions, use the
199 * alt_group's flattened byte-offset-addressed CFI
200 * array.
201 */
202 for (i = 0; i < alt_group_len(alt_group); i++) {
203 struct cfi_state *cfi = alt_group->cfi[i];
204 if (!cfi)
205 continue;
206 if (init_orc_entry(&orc, cfi))
207 return -1;
208 if (!memcmp(&prev_orc, &orc, sizeof(orc)))
209 continue;
210 if (orc_list_add(&orc_list, &orc, insn->sec,
211 insn->offset + i))
212 return -1;
213 nr++;
214 prev_orc = orc;
215 empty = false;
216 }
217
218 /* Skip to the end of the alt_group */
219 insn = alt_group->last_insn;
220 }
221
222 /* Add a section terminator */
223 if (!empty) {
224 orc_list_add(&orc_list, &null, sec, sec->len);
225 nr++;
226 }
227 }
228 if (!nr)
229 return 0;
230
231 /* Create .orc_unwind, .orc_unwind_ip and .rela.orc_unwind_ip sections: */
232 sec = find_section_by_name(file->elf, ".orc_unwind");
233 if (sec) {
234 WARN("file already has .orc_unwind section, skipping");
235 return -1;
236 }
237 orc_sec = elf_create_section(file->elf, ".orc_unwind", 0,
238 sizeof(struct orc_entry), nr);
239 if (!orc_sec)
240 return -1;
241
242 sec = elf_create_section(file->elf, ".orc_unwind_ip", 0, sizeof(int), nr);
243 if (!sec)
244 return -1;
245 ip_rsec = elf_create_reloc_section(file->elf, sec, SHT_RELA);
246 if (!ip_rsec)
247 return -1;
248
249 /* Write ORC entries to sections: */
250 list_for_each_entry(entry, &orc_list, list) {
251 if (write_orc_entry(file->elf, orc_sec, ip_rsec, idx++,
252 entry->insn_sec, entry->insn_off,
253 &entry->orc))
254 return -1;
255 }
256
257 if (elf_rebuild_reloc_section(file->elf, ip_rsec))
258 return -1;
259
260 return 0;
261}