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
22 #include <asm/text-patching.h>
23 #include <asm/page.h>
24 #include <asm/pgtable.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_RANDOMIZE_BASE
40 static unsigned long module_load_offset;
41
42 /* Mutex protects the module_load_offset. */
43 static DEFINE_MUTEX(module_kaslr_mutex);
44
get_module_load_offset(void)45 static unsigned long int get_module_load_offset(void)
46 {
47 if (kaslr_enabled()) {
48 mutex_lock(&module_kaslr_mutex);
49 /*
50 * Calculate the module_load_offset the first time this
51 * code is called. Once calculated it stays the same until
52 * reboot.
53 */
54 if (module_load_offset == 0)
55 module_load_offset =
56 (get_random_int() % 1024 + 1) * PAGE_SIZE;
57 mutex_unlock(&module_kaslr_mutex);
58 }
59 return module_load_offset;
60 }
61 #else
get_module_load_offset(void)62 static unsigned long int get_module_load_offset(void)
63 {
64 return 0;
65 }
66 #endif
67
module_alloc(unsigned long size)68 void *module_alloc(unsigned long size)
69 {
70 void *p;
71
72 if (PAGE_ALIGN(size) > MODULES_LEN)
73 return NULL;
74
75 p = __vmalloc_node_range(size, MODULE_ALIGN,
76 MODULES_VADDR + get_module_load_offset(),
77 MODULES_END, GFP_KERNEL,
78 PAGE_KERNEL, 0, NUMA_NO_NODE,
79 __builtin_return_address(0));
80 if (p && (kasan_module_alloc(p, size) < 0)) {
81 vfree(p);
82 return NULL;
83 }
84
85 return p;
86 }
87
88 #ifdef CONFIG_X86_32
apply_relocate(Elf32_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * me)89 int apply_relocate(Elf32_Shdr *sechdrs,
90 const char *strtab,
91 unsigned int symindex,
92 unsigned int relsec,
93 struct module *me)
94 {
95 unsigned int i;
96 Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
97 Elf32_Sym *sym;
98 uint32_t *location;
99
100 DEBUGP("Applying relocate section %u to %u\n",
101 relsec, sechdrs[relsec].sh_info);
102 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
103 /* This is where to make the change */
104 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
105 + rel[i].r_offset;
106 /* This is the symbol it is referring to. Note that all
107 undefined symbols have been resolved. */
108 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
109 + ELF32_R_SYM(rel[i].r_info);
110
111 switch (ELF32_R_TYPE(rel[i].r_info)) {
112 case R_386_32:
113 /* We add the value into the location given */
114 *location += sym->st_value;
115 break;
116 case R_386_PC32:
117 case R_386_PLT32:
118 /* Add the value, subtract its position */
119 *location += sym->st_value - (uint32_t)location;
120 break;
121 default:
122 pr_err("%s: Unknown relocation: %u\n",
123 me->name, ELF32_R_TYPE(rel[i].r_info));
124 return -ENOEXEC;
125 }
126 }
127 return 0;
128 }
129 #else /*X86_64*/
apply_relocate_add(Elf64_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * me)130 int apply_relocate_add(Elf64_Shdr *sechdrs,
131 const char *strtab,
132 unsigned int symindex,
133 unsigned int relsec,
134 struct module *me)
135 {
136 unsigned int i;
137 Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
138 Elf64_Sym *sym;
139 void *loc;
140 u64 val;
141
142 DEBUGP("Applying relocate section %u to %u\n",
143 relsec, sechdrs[relsec].sh_info);
144 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
145 /* This is where to make the change */
146 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
147 + rel[i].r_offset;
148
149 /* This is the symbol it is referring to. Note that all
150 undefined symbols have been resolved. */
151 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
152 + ELF64_R_SYM(rel[i].r_info);
153
154 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
155 (int)ELF64_R_TYPE(rel[i].r_info),
156 sym->st_value, rel[i].r_addend, (u64)loc);
157
158 val = sym->st_value + rel[i].r_addend;
159
160 switch (ELF64_R_TYPE(rel[i].r_info)) {
161 case R_X86_64_NONE:
162 break;
163 case R_X86_64_64:
164 if (*(u64 *)loc != 0)
165 goto invalid_relocation;
166 *(u64 *)loc = val;
167 break;
168 case R_X86_64_32:
169 if (*(u32 *)loc != 0)
170 goto invalid_relocation;
171 *(u32 *)loc = val;
172 if (val != *(u32 *)loc)
173 goto overflow;
174 break;
175 case R_X86_64_32S:
176 if (*(s32 *)loc != 0)
177 goto invalid_relocation;
178 *(s32 *)loc = val;
179 if ((s64)val != *(s32 *)loc)
180 goto overflow;
181 break;
182 case R_X86_64_PC32:
183 case R_X86_64_PLT32:
184 if (*(u32 *)loc != 0)
185 goto invalid_relocation;
186 val -= (u64)loc;
187 *(u32 *)loc = val;
188 #if 0
189 if ((s64)val != *(s32 *)loc)
190 goto overflow;
191 #endif
192 break;
193 case R_X86_64_PC64:
194 if (*(u64 *)loc != 0)
195 goto invalid_relocation;
196 val -= (u64)loc;
197 *(u64 *)loc = val;
198 break;
199 case R_X86_64_8:
200 if (!strncmp(strtab + sym->st_name, "__typeid__", 10))
201 break;
202 /* fallthrough */
203 default:
204 pr_err("%s: Unknown rela relocation: %llu\n",
205 me->name, ELF64_R_TYPE(rel[i].r_info));
206 return -ENOEXEC;
207 }
208 }
209 return 0;
210
211 invalid_relocation:
212 pr_err("x86/modules: Skipping invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
213 (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
214 return -ENOEXEC;
215
216 overflow:
217 pr_err("overflow in relocation type %d val %Lx\n",
218 (int)ELF64_R_TYPE(rel[i].r_info), val);
219 pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
220 me->name);
221 return -ENOEXEC;
222 }
223 #endif
224
module_finalize(const Elf_Ehdr * hdr,const Elf_Shdr * sechdrs,struct module * me)225 int module_finalize(const Elf_Ehdr *hdr,
226 const Elf_Shdr *sechdrs,
227 struct module *me)
228 {
229 const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
230 *para = NULL, *orc = NULL, *orc_ip = 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(".text", secstrings + s->sh_name))
235 text = s;
236 if (!strcmp(".altinstructions", secstrings + s->sh_name))
237 alt = s;
238 if (!strcmp(".smp_locks", secstrings + s->sh_name))
239 locks = s;
240 if (!strcmp(".parainstructions", secstrings + s->sh_name))
241 para = s;
242 if (!strcmp(".orc_unwind", secstrings + s->sh_name))
243 orc = s;
244 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
245 orc_ip = s;
246 }
247
248 if (alt) {
249 /* patch .altinstructions */
250 void *aseg = (void *)alt->sh_addr;
251 apply_alternatives(aseg, aseg + alt->sh_size);
252 }
253 if (locks && text) {
254 void *lseg = (void *)locks->sh_addr;
255 void *tseg = (void *)text->sh_addr;
256 alternatives_smp_module_add(me, me->name,
257 lseg, lseg + locks->sh_size,
258 tseg, tseg + text->sh_size);
259 }
260
261 if (para) {
262 void *pseg = (void *)para->sh_addr;
263 apply_paravirt(pseg, pseg + para->sh_size);
264 }
265
266 /* make jump label nops */
267 jump_label_apply_nops(me);
268
269 if (orc && orc_ip)
270 unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size,
271 (void *)orc->sh_addr, orc->sh_size);
272
273 return 0;
274 }
275
module_arch_cleanup(struct module * mod)276 void module_arch_cleanup(struct module *mod)
277 {
278 alternatives_smp_module_del(mod);
279 }
280