projects/linux·blob master · refs

312 lines · 7.7 KiB

1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Kernel module help for x86.
3 Copyright (C) 2001 Rusty Russell.
4
5*/
6
7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8
9#include <linux/moduleloader.h>
10#include <linux/elf.h>
11#include <linux/vmalloc.h>
12#include <linux/fs.h>
13#include <linux/string.h>
14#include <linux/kernel.h>
15#include <linux/kasan.h>
16#include <linux/bug.h>
17#include <linux/mm.h>
18#include <linux/gfp.h>
19#include <linux/jump_label.h>
20#include <linux/random.h>
21#include <linux/memory.h>
22
23#include <asm/text-patching.h>
24#include <asm/page.h>
25#include <asm/setup.h>
26#include <asm/unwind.h>
27
28#if 0
29#define DEBUGP(fmt, ...) \
30 printk(KERN_DEBUG fmt, ##__VA_ARGS__)
31#else
32#define DEBUGP(fmt, ...) \
33do { \
34 if (0) \
35 printk(KERN_DEBUG fmt, ##__VA_ARGS__); \
36} while (0)
37#endif
38
39#ifdef CONFIG_X86_32
40int apply_relocate(Elf32_Shdr *sechdrs,
41 const char *strtab,
42 unsigned int symindex,
43 unsigned int relsec,
44 struct module *me)
45{
46 unsigned int i;
47 Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
48 Elf32_Sym *sym;
49 uint32_t *location;
50
51 DEBUGP("Applying relocate section %u to %u\n",
52 relsec, sechdrs[relsec].sh_info);
53 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
54 /* This is where to make the change */
55 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
56 + rel[i].r_offset;
57 /* This is the symbol it is referring to. Note that all
58 undefined symbols have been resolved. */
59 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
60 + ELF32_R_SYM(rel[i].r_info);
61
62 switch (ELF32_R_TYPE(rel[i].r_info)) {
63 case R_386_32:
64 /* We add the value into the location given */
65 *location += sym->st_value;
66 break;
67 case R_386_PC32:
68 case R_386_PLT32:
69 /* Add the value, subtract its position */
70 *location += sym->st_value - (uint32_t)location;
71 break;
72 default:
73 pr_err("%s: Unknown relocation: %u\n",
74 me->name, ELF32_R_TYPE(rel[i].r_info));
75 return -ENOEXEC;
76 }
77 }
78 return 0;
79}
80#else /*X86_64*/
81static int __write_relocate_add(Elf64_Shdr *sechdrs,
82 const char *strtab,
83 unsigned int symindex,
84 unsigned int relsec,
85 struct module *me,
86 void *(*write)(void *dest, const void *src, size_t len),
87 bool apply)
88{
89 unsigned int i;
90 Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
91 Elf64_Sym *sym;
92 void *loc;
93 u64 val;
94 u64 zero = 0ULL;
95
96 DEBUGP("%s relocate section %u to %u\n",
97 apply ? "Applying" : "Clearing",
98 relsec, sechdrs[relsec].sh_info);
99
100 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
101 size_t size;
102
103 /* This is where to make the change */
104 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
105 + rel[i].r_offset;
106
107 /* This is the symbol it is referring to. Note that all
108 undefined symbols have been resolved. */
109 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
110 + ELF64_R_SYM(rel[i].r_info);
111
112 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
113 (int)ELF64_R_TYPE(rel[i].r_info),
114 sym->st_value, rel[i].r_addend, (u64)loc);
115
116 val = sym->st_value + rel[i].r_addend;
117
118 switch (ELF64_R_TYPE(rel[i].r_info)) {
119 case R_X86_64_NONE:
120 continue; /* nothing to write */
121 case R_X86_64_64:
122 size = 8;
123 break;
124 case R_X86_64_32:
125 if (val != *(u32 *)&val)
126 goto overflow;
127 size = 4;
128 break;
129 case R_X86_64_32S:
130 if ((s64)val != *(s32 *)&val)
131 goto overflow;
132 size = 4;
133 break;
134 case R_X86_64_PC32:
135 case R_X86_64_PLT32:
136 val -= (u64)loc;
137 size = 4;
138 break;
139 case R_X86_64_PC64:
140 val -= (u64)loc;
141 size = 8;
142 break;
143 default:
144 pr_err("%s: Unknown rela relocation: %llu\n",
145 me->name, ELF64_R_TYPE(rel[i].r_info));
146 return -ENOEXEC;
147 }
148
149 if (apply) {
150 if (memcmp(loc, &zero, size)) {
151 pr_err("x86/modules: Invalid relocation target, existing value is nonzero for sec %u, idx %u, type %d, loc %lx, val %llx\n",
152 relsec, i, (int)ELF64_R_TYPE(rel[i].r_info),
153 (unsigned long)loc, val);
154 return -ENOEXEC;
155 }
156 write(loc, &val, size);
157 } else {
158 if (memcmp(loc, &val, size)) {
159 pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for sec %u, idx %u, type %d, loc %lx, val %llx\n",
160 relsec, i, (int)ELF64_R_TYPE(rel[i].r_info),
161 (unsigned long)loc, val);
162 return -ENOEXEC;
163 }
164 write(loc, &zero, size);
165 }
166 }
167 return 0;
168
169overflow:
170 pr_err("overflow in relocation type %d val %llx sec %u idx %d\n",
171 (int)ELF64_R_TYPE(rel[i].r_info), val, relsec, i);
172 pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
173 me->name);
174 return -ENOEXEC;
175}
176
177static int write_relocate_add(Elf64_Shdr *sechdrs,
178 const char *strtab,
179 unsigned int symindex,
180 unsigned int relsec,
181 struct module *me,
182 bool apply)
183{
184 int ret;
185 bool early = me->state == MODULE_STATE_UNFORMED;
186 void *(*write)(void *, const void *, size_t) = memcpy;
187
188 if (!early) {
189 write = text_poke;
190 mutex_lock(&text_mutex);
191 }
192
193 ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me,
194 write, apply);
195
196 if (!early) {
197 smp_text_poke_sync_each_cpu();
198 mutex_unlock(&text_mutex);
199 }
200
201 return ret;
202}
203
204int apply_relocate_add(Elf64_Shdr *sechdrs,
205 const char *strtab,
206 unsigned int symindex,
207 unsigned int relsec,
208 struct module *me)
209{
210 return write_relocate_add(sechdrs, strtab, symindex, relsec, me, true);
211}
212
213#ifdef CONFIG_LIVEPATCH
214void clear_relocate_add(Elf64_Shdr *sechdrs,
215 const char *strtab,
216 unsigned int symindex,
217 unsigned int relsec,
218 struct module *me)
219{
220 write_relocate_add(sechdrs, strtab, symindex, relsec, me, false);
221}
222#endif
223
224#endif
225
226int module_finalize(const Elf_Ehdr *hdr,
227 const Elf_Shdr *sechdrs,
228 struct module *me)
229{
230 const Elf_Shdr *s, *alt = NULL,
231 *orc = NULL, *orc_ip = NULL,
232 *retpolines = NULL, *returns = NULL, *ibt_endbr = NULL,
233 *calls = NULL, *cfi = NULL;
234 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
235
236 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
237 if (!strcmp(".altinstructions", secstrings + s->sh_name))
238 alt = s;
239 if (!strcmp(".orc_unwind", secstrings + s->sh_name))
240 orc = s;
241 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
242 orc_ip = s;
243 if (!strcmp(".retpoline_sites", secstrings + s->sh_name))
244 retpolines = s;
245 if (!strcmp(".return_sites", secstrings + s->sh_name))
246 returns = s;
247 if (!strcmp(".call_sites", secstrings + s->sh_name))
248 calls = s;
249 if (!strcmp(".cfi_sites", secstrings + s->sh_name))
250 cfi = s;
251 if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name))
252 ibt_endbr = s;
253 }
254
255 its_init_mod(me);
256
257 if (retpolines || cfi) {
258 void *rseg = NULL, *cseg = NULL;
259 unsigned int rsize = 0, csize = 0;
260
261 if (retpolines) {
262 rseg = (void *)retpolines->sh_addr;
263 rsize = retpolines->sh_size;
264 }
265
266 if (cfi) {
267 cseg = (void *)cfi->sh_addr;
268 csize = cfi->sh_size;
269 }
270
271 apply_fineibt(rseg, rseg + rsize, cseg, cseg + csize);
272 }
273 if (retpolines) {
274 void *rseg = (void *)retpolines->sh_addr;
275 apply_retpolines(rseg, rseg + retpolines->sh_size);
276 }
277
278 its_fini_mod(me);
279
280 if (returns) {
281 void *rseg = (void *)returns->sh_addr;
282 apply_returns(rseg, rseg + returns->sh_size);
283 }
284 if (calls) {
285 struct callthunk_sites cs = {};
286
287 cs.call_start = (void *)calls->sh_addr;
288 cs.call_end = (void *)calls->sh_addr + calls->sh_size;
289
290 callthunks_patch_module_calls(&cs, me);
291 }
292 if (alt) {
293 /* patch .altinstructions */
294 void *aseg = (void *)alt->sh_addr;
295 apply_alternatives(aseg, aseg + alt->sh_size);
296 }
297 if (ibt_endbr) {
298 void *iseg = (void *)ibt_endbr->sh_addr;
299 apply_seal_endbr(iseg, iseg + ibt_endbr->sh_size);
300 }
301
302 if (orc && orc_ip)
303 unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size,
304 (void *)orc->sh_addr, orc->sh_size);
305
306 return 0;
307}
308
309void module_arch_cleanup(struct module *mod)
310{
311 its_free_mod(mod);
312}