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