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