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, ...) \
33 do { \
34 if (0) \
35 printk(KERN_DEBUG fmt, ##__VA_ARGS__); \
36 } while (0)
37 #endif
38
39 #ifdef CONFIG_X86_32
apply_relocate(Elf32_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * me)40 int 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*/
__write_relocate_add(Elf64_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * me,void * (* write)(void * dest,const void * src,size_t len),bool apply)81 static 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 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
100 size_t size;
101
102 /* This is where to make the change */
103 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
104 + rel[i].r_offset;
105
106 /* This is the symbol it is referring to. Note that all
107 undefined symbols have been resolved. */
108 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
109 + ELF64_R_SYM(rel[i].r_info);
110
111 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
112 (int)ELF64_R_TYPE(rel[i].r_info),
113 sym->st_value, rel[i].r_addend, (u64)loc);
114
115 val = sym->st_value + rel[i].r_addend;
116
117 switch (ELF64_R_TYPE(rel[i].r_info)) {
118 case R_X86_64_NONE:
119 continue; /* nothing to write */
120 case R_X86_64_64:
121 size = 8;
122 break;
123 case R_X86_64_32:
124 if (val != *(u32 *)&val)
125 goto overflow;
126 size = 4;
127 break;
128 case R_X86_64_32S:
129 if ((s64)val != *(s32 *)&val)
130 goto overflow;
131 size = 4;
132 break;
133 case R_X86_64_PC32:
134 case R_X86_64_PLT32:
135 val -= (u64)loc;
136 size = 4;
137 break;
138 case R_X86_64_PC64:
139 val -= (u64)loc;
140 size = 8;
141 break;
142 default:
143 pr_err("%s: Unknown rela relocation: %llu\n",
144 me->name, ELF64_R_TYPE(rel[i].r_info));
145 return -ENOEXEC;
146 }
147
148 if (apply) {
149 if (memcmp(loc, &zero, size)) {
150 pr_err("x86/modules: Invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
151 (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
152 return -ENOEXEC;
153 }
154 write(loc, &val, size);
155 } else {
156 if (memcmp(loc, &val, size)) {
157 pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for type %d, loc %p, val %Lx\n",
158 (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
159 return -ENOEXEC;
160 }
161 write(loc, &zero, size);
162 }
163 }
164 return 0;
165
166 overflow:
167 pr_err("overflow in relocation type %d val %Lx\n",
168 (int)ELF64_R_TYPE(rel[i].r_info), val);
169 pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
170 me->name);
171 return -ENOEXEC;
172 }
173
write_relocate_add(Elf64_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * me,bool apply)174 static int write_relocate_add(Elf64_Shdr *sechdrs,
175 const char *strtab,
176 unsigned int symindex,
177 unsigned int relsec,
178 struct module *me,
179 bool apply)
180 {
181 int ret;
182 bool early = me->state == MODULE_STATE_UNFORMED;
183 void *(*write)(void *, const void *, size_t) = memcpy;
184
185 if (!early) {
186 write = text_poke;
187 mutex_lock(&text_mutex);
188 }
189
190 ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me,
191 write, apply);
192
193 if (!early) {
194 text_poke_sync();
195 mutex_unlock(&text_mutex);
196 }
197
198 return ret;
199 }
200
apply_relocate_add(Elf64_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * me)201 int apply_relocate_add(Elf64_Shdr *sechdrs,
202 const char *strtab,
203 unsigned int symindex,
204 unsigned int relsec,
205 struct module *me)
206 {
207 return write_relocate_add(sechdrs, strtab, symindex, relsec, me, true);
208 }
209
210 #ifdef CONFIG_LIVEPATCH
clear_relocate_add(Elf64_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * me)211 void clear_relocate_add(Elf64_Shdr *sechdrs,
212 const char *strtab,
213 unsigned int symindex,
214 unsigned int relsec,
215 struct module *me)
216 {
217 write_relocate_add(sechdrs, strtab, symindex, relsec, me, false);
218 }
219 #endif
220
221 #endif
222
module_finalize(const Elf_Ehdr * hdr,const Elf_Shdr * sechdrs,struct module * me)223 int module_finalize(const Elf_Ehdr *hdr,
224 const Elf_Shdr *sechdrs,
225 struct module *me)
226 {
227 const Elf_Shdr *s, *alt = NULL, *locks = NULL,
228 *orc = NULL, *orc_ip = NULL,
229 *retpolines = NULL, *returns = NULL, *ibt_endbr = NULL,
230 *calls = NULL, *cfi = NULL;
231 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
232
233 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
234 if (!strcmp(".altinstructions", secstrings + s->sh_name))
235 alt = s;
236 if (!strcmp(".smp_locks", secstrings + s->sh_name))
237 locks = s;
238 if (!strcmp(".orc_unwind", secstrings + s->sh_name))
239 orc = s;
240 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
241 orc_ip = s;
242 if (!strcmp(".retpoline_sites", secstrings + s->sh_name))
243 retpolines = s;
244 if (!strcmp(".return_sites", secstrings + s->sh_name))
245 returns = s;
246 if (!strcmp(".call_sites", secstrings + s->sh_name))
247 calls = s;
248 if (!strcmp(".cfi_sites", secstrings + s->sh_name))
249 cfi = s;
250 if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name))
251 ibt_endbr = s;
252 }
253
254 if (retpolines || cfi) {
255 void *rseg = NULL, *cseg = NULL;
256 unsigned int rsize = 0, csize = 0;
257
258 if (retpolines) {
259 rseg = (void *)retpolines->sh_addr;
260 rsize = retpolines->sh_size;
261 }
262
263 if (cfi) {
264 cseg = (void *)cfi->sh_addr;
265 csize = cfi->sh_size;
266 }
267
268 apply_fineibt(rseg, rseg + rsize, cseg, cseg + csize);
269 }
270 if (retpolines) {
271 void *rseg = (void *)retpolines->sh_addr;
272 apply_retpolines(rseg, rseg + retpolines->sh_size);
273 }
274 if (returns) {
275 void *rseg = (void *)returns->sh_addr;
276 apply_returns(rseg, rseg + returns->sh_size);
277 }
278 if (alt) {
279 /* patch .altinstructions */
280 void *aseg = (void *)alt->sh_addr;
281 apply_alternatives(aseg, aseg + alt->sh_size);
282 }
283 if (calls || alt) {
284 struct callthunk_sites cs = {};
285
286 if (calls) {
287 cs.call_start = (void *)calls->sh_addr;
288 cs.call_end = (void *)calls->sh_addr + calls->sh_size;
289 }
290
291 if (alt) {
292 cs.alt_start = (void *)alt->sh_addr;
293 cs.alt_end = (void *)alt->sh_addr + alt->sh_size;
294 }
295
296 callthunks_patch_module_calls(&cs, me);
297 }
298 if (ibt_endbr) {
299 void *iseg = (void *)ibt_endbr->sh_addr;
300 apply_seal_endbr(iseg, iseg + ibt_endbr->sh_size);
301 }
302 if (locks) {
303 void *lseg = (void *)locks->sh_addr;
304 void *text = me->mem[MOD_TEXT].base;
305 void *text_end = text + me->mem[MOD_TEXT].size;
306 alternatives_smp_module_add(me, me->name,
307 lseg, lseg + locks->sh_size,
308 text, text_end);
309 }
310
311 if (orc && orc_ip)
312 unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size,
313 (void *)orc->sh_addr, orc->sh_size);
314
315 return 0;
316 }
317
module_arch_cleanup(struct module * mod)318 void module_arch_cleanup(struct module *mod)
319 {
320 alternatives_smp_module_del(mod);
321 }
322