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 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#if defined(CONFIG_STACKPROTECTOR) && \
135 defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 170000
136 case R_X86_64_REX_GOTPCRELX: {
137 static unsigned long __percpu *const addr = &__stack_chk_guard;
138
139 if (sym->st_value != (u64)addr) {
140 pr_err("%s: Unsupported GOTPCREL relocation\n", me->name);
141 return -ENOEXEC;
142 }
143
144 val = (u64)&addr + rel[i].r_addend;
145 fallthrough;
146 }
147#endif
148 case R_X86_64_PC32:
149 case R_X86_64_PLT32:
150 val -= (u64)loc;
151 size = 4;
152 break;
153 case R_X86_64_PC64:
154 val -= (u64)loc;
155 size = 8;
156 break;
157 default:
158 pr_err("%s: Unknown rela relocation: %llu\n",
159 me->name, ELF64_R_TYPE(rel[i].r_info));
160 return -ENOEXEC;
161 }
162
163 if (apply) {
164 if (memcmp(p: loc, q: &zero, size)) {
165 pr_err("x86/modules: Invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
166 (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
167 return -ENOEXEC;
168 }
169 write(loc, &val, size);
170 } else {
171 if (memcmp(p: loc, q: &val, size)) {
172 pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for type %d, loc %p, val %Lx\n",
173 (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
174 return -ENOEXEC;
175 }
176 write(loc, &zero, size);
177 }
178 }
179 return 0;
180
181overflow:
182 pr_err("overflow in relocation type %d val %Lx\n",
183 (int)ELF64_R_TYPE(rel[i].r_info), val);
184 pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
185 me->name);
186 return -ENOEXEC;
187}
188
189static int write_relocate_add(Elf64_Shdr *sechdrs,
190 const char *strtab,
191 unsigned int symindex,
192 unsigned int relsec,
193 struct module *me,
194 bool apply)
195{
196 int ret;
197 bool early = me->state == MODULE_STATE_UNFORMED;
198 void *(*write)(void *, const void *, size_t) = memcpy;
199
200 if (!early) {
201 write = text_poke;
202 mutex_lock(&text_mutex);
203 }
204
205 ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me,
206 write, apply);
207
208 if (!early) {
209 smp_text_poke_sync_each_cpu();
210 mutex_unlock(lock: &text_mutex);
211 }
212
213 return ret;
214}
215
216int apply_relocate_add(Elf64_Shdr *sechdrs,
217 const char *strtab,
218 unsigned int symindex,
219 unsigned int relsec,
220 struct module *me)
221{
222 return write_relocate_add(sechdrs, strtab, symindex, relsec, me, apply: true);
223}
224
225#ifdef CONFIG_LIVEPATCH
226void clear_relocate_add(Elf64_Shdr *sechdrs,
227 const char *strtab,
228 unsigned int symindex,
229 unsigned int relsec,
230 struct module *me)
231{
232 write_relocate_add(sechdrs, strtab, symindex, relsec, me, false);
233}
234#endif
235
236#endif
237
238int module_finalize(const Elf_Ehdr *hdr,
239 const Elf_Shdr *sechdrs,
240 struct module *me)
241{
242 const Elf_Shdr *s, *alt = NULL, *locks = NULL,
243 *orc = NULL, *orc_ip = NULL,
244 *retpolines = NULL, *returns = NULL, *ibt_endbr = NULL,
245 *calls = NULL, *cfi = NULL;
246 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
247
248 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
249 if (!strcmp(".altinstructions", secstrings + s->sh_name))
250 alt = s;
251 if (!strcmp(".smp_locks", secstrings + s->sh_name))
252 locks = s;
253 if (!strcmp(".orc_unwind", secstrings + s->sh_name))
254 orc = s;
255 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
256 orc_ip = s;
257 if (!strcmp(".retpoline_sites", secstrings + s->sh_name))
258 retpolines = s;
259 if (!strcmp(".return_sites", secstrings + s->sh_name))
260 returns = s;
261 if (!strcmp(".call_sites", secstrings + s->sh_name))
262 calls = s;
263 if (!strcmp(".cfi_sites", secstrings + s->sh_name))
264 cfi = s;
265 if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name))
266 ibt_endbr = s;
267 }
268
269 its_init_mod(mod: me);
270
271 if (retpolines || cfi) {
272 void *rseg = NULL, *cseg = NULL;
273 unsigned int rsize = 0, csize = 0;
274
275 if (retpolines) {
276 rseg = (void *)retpolines->sh_addr;
277 rsize = retpolines->sh_size;
278 }
279
280 if (cfi) {
281 cseg = (void *)cfi->sh_addr;
282 csize = cfi->sh_size;
283 }
284
285 apply_fineibt(start_retpoline: rseg, end_retpoine: rseg + rsize, start_cfi: cseg, end_cfi: cseg + csize);
286 }
287 if (retpolines) {
288 void *rseg = (void *)retpolines->sh_addr;
289 apply_retpolines(start: rseg, end: rseg + retpolines->sh_size);
290 }
291
292 its_fini_mod(mod: me);
293
294 if (returns) {
295 void *rseg = (void *)returns->sh_addr;
296 apply_returns(start: rseg, end: rseg + returns->sh_size);
297 }
298 if (calls) {
299 struct callthunk_sites cs = {};
300
301 cs.call_start = (void *)calls->sh_addr;
302 cs.call_end = (void *)calls->sh_addr + calls->sh_size;
303
304 callthunks_patch_module_calls(sites: &cs, mod: me);
305 }
306 if (alt) {
307 /* patch .altinstructions */
308 void *aseg = (void *)alt->sh_addr;
309 apply_alternatives(start: aseg, end: aseg + alt->sh_size);
310 }
311 if (ibt_endbr) {
312 void *iseg = (void *)ibt_endbr->sh_addr;
313 apply_seal_endbr(start: iseg, end: iseg + ibt_endbr->sh_size);
314 }
315 if (locks) {
316 void *lseg = (void *)locks->sh_addr;
317 void *text = me->mem[MOD_TEXT].base;
318 void *text_end = text + me->mem[MOD_TEXT].size;
319 alternatives_smp_module_add(mod: me, name: me->name,
320 locks: lseg, locks_end: lseg + locks->sh_size,
321 text, text_end);
322 }
323
324 if (orc && orc_ip)
325 unwind_module_init(mod: me, orc_ip: (void *)orc_ip->sh_addr, orc_ip_size: orc_ip->sh_size,
326 orc: (void *)orc->sh_addr, orc_size: orc->sh_size);
327
328 return 0;
329}
330
331void module_arch_cleanup(struct module *mod)
332{
333 alternatives_smp_module_del(mod);
334 its_free_mod(mod);
335}
336

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