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
init_orc_entry(struct orc_entry * orc,struct cfi_state * cfi)16 static 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
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)84 static int write_orc_entry(struct elf *elf, struct section *orc_sec,
85 struct section *ip_sec, unsigned int idx,
86 struct section *insn_sec, unsigned long insn_off,
87 struct orc_entry *o)
88 {
89 struct orc_entry *orc;
90
91 /* populate ORC data */
92 orc = (struct orc_entry *)orc_sec->data->d_buf + idx;
93 memcpy(orc, o, sizeof(*orc));
94 orc->sp_offset = bswap_if_needed(orc->sp_offset);
95 orc->bp_offset = bswap_if_needed(orc->bp_offset);
96
97 /* populate reloc for ip */
98 if (elf_add_reloc_to_insn(elf, ip_sec, idx * sizeof(int), R_X86_64_PC32,
99 insn_sec, insn_off))
100 return -1;
101
102 return 0;
103 }
104
105 struct orc_list_entry {
106 struct list_head list;
107 struct orc_entry orc;
108 struct section *insn_sec;
109 unsigned long insn_off;
110 };
111
orc_list_add(struct list_head * orc_list,struct orc_entry * orc,struct section * sec,unsigned long offset)112 static int orc_list_add(struct list_head *orc_list, struct orc_entry *orc,
113 struct section *sec, unsigned long offset)
114 {
115 struct orc_list_entry *entry = malloc(sizeof(*entry));
116
117 if (!entry) {
118 WARN("malloc failed");
119 return -1;
120 }
121
122 entry->orc = *orc;
123 entry->insn_sec = sec;
124 entry->insn_off = offset;
125
126 list_add_tail(&entry->list, orc_list);
127 return 0;
128 }
129
alt_group_len(struct alt_group * alt_group)130 static unsigned long alt_group_len(struct alt_group *alt_group)
131 {
132 return alt_group->last_insn->offset +
133 alt_group->last_insn->len -
134 alt_group->first_insn->offset;
135 }
136
orc_create(struct objtool_file * file)137 int orc_create(struct objtool_file *file)
138 {
139 struct section *sec, *orc_sec;
140 unsigned int nr = 0, idx = 0;
141 struct orc_list_entry *entry;
142 struct list_head orc_list;
143
144 struct orc_entry null = {
145 .sp_reg = ORC_REG_UNDEFINED,
146 .bp_reg = ORC_REG_UNDEFINED,
147 .type = UNWIND_HINT_TYPE_CALL,
148 };
149
150 /* Build a deduplicated list of ORC entries: */
151 INIT_LIST_HEAD(&orc_list);
152 for_each_sec(file, sec) {
153 struct orc_entry orc, prev_orc = {0};
154 struct instruction *insn;
155 bool empty = true;
156
157 if (!sec->text)
158 continue;
159
160 sec_for_each_insn(file, sec, insn) {
161 struct alt_group *alt_group = insn->alt_group;
162 int i;
163
164 if (!alt_group) {
165 if (init_orc_entry(&orc, &insn->cfi))
166 return -1;
167 if (!memcmp(&prev_orc, &orc, sizeof(orc)))
168 continue;
169 if (orc_list_add(&orc_list, &orc, sec,
170 insn->offset))
171 return -1;
172 nr++;
173 prev_orc = orc;
174 empty = false;
175 continue;
176 }
177
178 /*
179 * Alternatives can have different stack layout
180 * possibilities (but they shouldn't conflict).
181 * Instead of traversing the instructions, use the
182 * alt_group's flattened byte-offset-addressed CFI
183 * array.
184 */
185 for (i = 0; i < alt_group_len(alt_group); i++) {
186 struct cfi_state *cfi = alt_group->cfi[i];
187 if (!cfi)
188 continue;
189 if (init_orc_entry(&orc, cfi))
190 return -1;
191 if (!memcmp(&prev_orc, &orc, sizeof(orc)))
192 continue;
193 if (orc_list_add(&orc_list, &orc, insn->sec,
194 insn->offset + i))
195 return -1;
196 nr++;
197 prev_orc = orc;
198 empty = false;
199 }
200
201 /* Skip to the end of the alt_group */
202 insn = alt_group->last_insn;
203 }
204
205 /* Add a section terminator */
206 if (!empty) {
207 orc_list_add(&orc_list, &null, sec, sec->sh.sh_size);
208 nr++;
209 }
210 }
211 if (!nr)
212 return 0;
213
214 /* Create .orc_unwind, .orc_unwind_ip and .rela.orc_unwind_ip sections: */
215 sec = find_section_by_name(file->elf, ".orc_unwind");
216 if (sec) {
217 WARN("file already has .orc_unwind section, skipping");
218 return -1;
219 }
220 orc_sec = elf_create_section(file->elf, ".orc_unwind", 0,
221 sizeof(struct orc_entry), nr);
222 if (!orc_sec)
223 return -1;
224
225 sec = elf_create_section(file->elf, ".orc_unwind_ip", 0, sizeof(int), nr);
226 if (!sec)
227 return -1;
228
229 /* Write ORC entries to sections: */
230 list_for_each_entry(entry, &orc_list, list) {
231 if (write_orc_entry(file->elf, orc_sec, sec, idx++,
232 entry->insn_sec, entry->insn_off,
233 &entry->orc))
234 return -1;
235 }
236
237 return 0;
238 }
239
