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