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#include <linux/stackprotector.h>
23
24#include <asm/text-patching.h>
25#include <asm/page.h>
26#include <asm/setup.h>
27#include <asm/unwind.h>
28
29#if 0
30#define DEBUGP(fmt, ...) \
31 printk(KERN_DEBUG fmt, ##__VA_ARGS__)
32#else
33#define DEBUGP(fmt, ...) \
34do { \
35 if (0) \
36 printk(KERN_DEBUG fmt, ##__VA_ARGS__); \
37} while (0)
38#endif
39
40#ifdef CONFIG_X86_32
41int apply_relocate(Elf32_Shdr *sechdrs,
42 const char *strtab,
43 unsigned int symindex,
44 unsigned int relsec,
45 struct module *me)
46{
47 unsigned int i;
48 Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
49 Elf32_Sym *sym;
50 uint32_t *location;
51
52 DEBUGP("Applying relocate section %u to %u\n",
53 relsec, sechdrs[relsec].sh_info);
54 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
55 /* This is where to make the change */
56 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
57 + rel[i].r_offset;
58 /* This is the symbol it is referring to. Note that all
59 undefined symbols have been resolved. */
60 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
61 + ELF32_R_SYM(rel[i].r_info);
62
63 switch (ELF32_R_TYPE(rel[i].r_info)) {
64 case R_386_32:
65 /* We add the value into the location given */
66 *location += sym->st_value;
67 break;
68 case R_386_PC32:
69 case R_386_PLT32:
70 /* Add the value, subtract its position */
71 *location += sym->st_value - (uint32_t)location;
72 break;
73 default:
74 pr_err("%s: Unknown relocation: %u\n",
75 me->name, ELF32_R_TYPE(rel[i].r_info));
76 return -ENOEXEC;
77 }
78 }
79 return 0;
80}
81#else /*X86_64*/
82static int __write_relocate_add(Elf64_Shdr *sechdrs,
83 const char *strtab,
84 unsigned int symindex,
85 unsigned int relsec,
86 struct module *me,
87 void *(*write)(void *dest, const void *src, size_t len),
88 bool apply)
89{
90 unsigned int i;
91 Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
92 Elf64_Sym *sym;
93 void *loc;
94 u64 val;
95 u64 zero = 0ULL;
96
97 DEBUGP("%s relocate section %u to %u\n",
98 apply ? "Applying" : "Clearing",
99 relsec, sechdrs[relsec].sh_info);
100
101 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
102 size_t size;
103
104 /* This is where to make the change */
105 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
106 + rel[i].r_offset;
107
108 /* This is the symbol it is referring to. Note that all
109 undefined symbols have been resolved. */
110 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
111 + ELF64_R_SYM(rel[i].r_info);
112
113 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
114 (int)ELF64_R_TYPE(rel[i].r_info),
115 sym->st_value, rel[i].r_addend, (u64)loc);
116
117 val = sym->st_value + rel[i].r_addend;
118
119 switch (ELF64_R_TYPE(rel[i].r_info)) {
120 case R_X86_64_NONE:
121 continue; /* nothing to write */
122 case R_X86_64_64:
123 size = 8;
124 break;
125 case R_X86_64_32:
126 if (val != *(u32 *)&val)
127 goto overflow;
128 size = 4;
129 break;
130 case R_X86_64_32S:
131 if ((s64)val != *(s32 *)&val)
132 goto overflow;
133 size = 4;
134 break;
135#if defined(CONFIG_STACKPROTECTOR) && \
136 defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 170000
137 case R_X86_64_REX_GOTPCRELX: {
138 static unsigned long __percpu *const addr = &__stack_chk_guard;
139
140 if (sym->st_value != (u64)addr) {
141 pr_err("%s: Unsupported GOTPCREL relocation\n", me->name);
142 return -ENOEXEC;
143 }
144
145 val = (u64)&addr + rel[i].r_addend;
146 fallthrough;
147 }
148#endif
149 case R_X86_64_PC32:
150 case R_X86_64_PLT32:
151 val -= (u64)loc;
152 size = 4;
153 break;
154 case R_X86_64_PC64:
155 val -= (u64)loc;
156 size = 8;
157 break;
158 default:
159 pr_err("%s: Unknown rela relocation: %llu\n",
160 me->name, ELF64_R_TYPE(rel[i].r_info));
161 return -ENOEXEC;
162 }
163
164 if (apply) {
165 if (memcmp(p: loc, q: &zero, size)) {
166 pr_err("x86/modules: Invalid relocation target, existing value is nonzero for sec %u, idx %u, type %d, loc %lx, val %llx\n",
167 relsec, i, (int)ELF64_R_TYPE(rel[i].r_info),
168 (unsigned long)loc, val);
169 return -ENOEXEC;
170 }
171 write(loc, &val, size);
172 } else {
173 if (memcmp(p: loc, q: &val, size)) {
174 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",
175 relsec, i, (int)ELF64_R_TYPE(rel[i].r_info),
176 (unsigned long)loc, val);
177 return -ENOEXEC;
178 }
179 write(loc, &zero, size);
180 }
181 }
182 return 0;
183
184overflow:
185 pr_err("overflow in relocation type %d val %llx sec %u idx %d\n",
186 (int)ELF64_R_TYPE(rel[i].r_info), val, relsec, i);
187 pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
188 me->name);
189 return -ENOEXEC;
190}
191
192static int write_relocate_add(Elf64_Shdr *sechdrs,
193 const char *strtab,
194 unsigned int symindex,
195 unsigned int relsec,
196 struct module *me,
197 bool apply)
198{
199 int ret;
200 bool early = me->state == MODULE_STATE_UNFORMED;
201 void *(*write)(void *, const void *, size_t) = memcpy;
202
203 if (!early) {
204 write = text_poke;
205 mutex_lock(&text_mutex);
206 }
207
208 ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me,
209 write, apply);
210
211 if (!early) {
212 smp_text_poke_sync_each_cpu();
213 mutex_unlock(lock: &text_mutex);
214 }
215
216 return ret;
217}
218
219int apply_relocate_add(Elf64_Shdr *sechdrs,
220 const char *strtab,
221 unsigned int symindex,
222 unsigned int relsec,
223 struct module *me)
224{
225 return write_relocate_add(sechdrs, strtab, symindex, relsec, me, apply: true);
226}
227
228#ifdef CONFIG_LIVEPATCH
229void clear_relocate_add(Elf64_Shdr *sechdrs,
230 const char *strtab,
231 unsigned int symindex,
232 unsigned int relsec,
233 struct module *me)
234{
235 write_relocate_add(sechdrs, strtab, symindex, relsec, me, false);
236}
237#endif
238
239#endif
240
241int module_finalize(const Elf_Ehdr *hdr,
242 const Elf_Shdr *sechdrs,
243 struct module *me)
244{
245 const Elf_Shdr *s, *alt = NULL, *locks = NULL,
246 *orc = NULL, *orc_ip = NULL,
247 *retpolines = NULL, *returns = NULL, *ibt_endbr = NULL,
248 *calls = NULL, *cfi = NULL;
249 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
250
251 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
252 if (!strcmp(".altinstructions", secstrings + s->sh_name))
253 alt = s;
254 if (!strcmp(".smp_locks", secstrings + s->sh_name))
255 locks = s;
256 if (!strcmp(".orc_unwind", secstrings + s->sh_name))
257 orc = s;
258 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
259 orc_ip = s;
260 if (!strcmp(".retpoline_sites", secstrings + s->sh_name))
261 retpolines = s;
262 if (!strcmp(".return_sites", secstrings + s->sh_name))
263 returns = s;
264 if (!strcmp(".call_sites", secstrings + s->sh_name))
265 calls = s;
266 if (!strcmp(".cfi_sites", secstrings + s->sh_name))
267 cfi = s;
268 if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name))
269 ibt_endbr = s;
270 }
271
272 its_init_mod(mod: me);
273
274 if (retpolines || cfi) {
275 void *rseg = NULL, *cseg = NULL;
276 unsigned int rsize = 0, csize = 0;
277
278 if (retpolines) {
279 rseg = (void *)retpolines->sh_addr;
280 rsize = retpolines->sh_size;
281 }
282
283 if (cfi) {
284 cseg = (void *)cfi->sh_addr;
285 csize = cfi->sh_size;
286 }
287
288 apply_fineibt(start_retpoline: rseg, end_retpoine: rseg + rsize, start_cfi: cseg, end_cfi: cseg + csize);
289 }
290 if (retpolines) {
291 void *rseg = (void *)retpolines->sh_addr;
292 apply_retpolines(start: rseg, end: rseg + retpolines->sh_size);
293 }
294
295 its_fini_mod(mod: me);
296
297 if (returns) {
298 void *rseg = (void *)returns->sh_addr;
299 apply_returns(start: rseg, end: rseg + returns->sh_size);
300 }
301 if (calls) {
302 struct callthunk_sites cs = {};
303
304 cs.call_start = (void *)calls->sh_addr;
305 cs.call_end = (void *)calls->sh_addr + calls->sh_size;
306
307 callthunks_patch_module_calls(sites: &cs, mod: me);
308 }
309 if (alt) {
310 /* patch .altinstructions */
311 void *aseg = (void *)alt->sh_addr;
312 apply_alternatives(start: aseg, end: aseg + alt->sh_size);
313 }
314 if (ibt_endbr) {
315 void *iseg = (void *)ibt_endbr->sh_addr;
316 apply_seal_endbr(start: iseg, end: iseg + ibt_endbr->sh_size);
317 }
318 if (locks) {
319 void *lseg = (void *)locks->sh_addr;
320 void *text = me->mem[MOD_TEXT].base;
321 void *text_end = text + me->mem[MOD_TEXT].size;
322 alternatives_smp_module_add(mod: me, name: me->name,
323 locks: lseg, locks_end: lseg + locks->sh_size,
324 text, text_end);
325 }
326
327 if (orc && orc_ip)
328 unwind_module_init(mod: me, orc_ip: (void *)orc_ip->sh_addr, orc_ip_size: orc_ip->sh_size,
329 orc: (void *)orc->sh_addr, orc_size: orc->sh_size);
330
331 return 0;
332}
333
334void module_arch_cleanup(struct module *mod)
335{
336 alternatives_smp_module_del(mod);
337 its_free_mod(mod);
338}
339

source code of linux/arch/x86/kernel/module.c