aboutsummaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/module.c
blob: e69f9882bf95a942ae1ce0f75efbf07301c9adc3 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
/*  Kernel module help for x86.
    Copyright (C) 2001 Rusty Russell.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/moduleloader.h>
#include <linux/elf.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/bug.h>
#include <linux/mm.h>
#include <linux/gfp.h>
#include <linux/jump_label.h>
#include <linux/random.h>

#include <asm/page.h>
#include <asm/pgtable.h>

#if 0
#define DEBUGP(fmt, ...)				\
	printk(KERN_DEBUG fmt, ##__VA_ARGS__)
#else
#define DEBUGP(fmt, ...)				\
do {							\
	if (0)						\
		printk(KERN_DEBUG fmt, ##__VA_ARGS__);	\
} while (0)
#endif

#ifdef CONFIG_RANDOMIZE_BASE
static unsigned long module_load_offset;
static int randomize_modules = 1;

/* Mutex protects the module_load_offset. */
static DEFINE_MUTEX(module_kaslr_mutex);

static int __init parse_nokaslr(char *p)
{
	randomize_modules = 0;
	return 0;
}
early_param("nokaslr", parse_nokaslr);

static unsigned long int get_module_load_offset(void)
{
	if (randomize_modules) {
		mutex_lock(&module_kaslr_mutex);
		/*
		 * Calculate the module_load_offset the first time this
		 * code is called. Once calculated it stays the same until
		 * reboot.
		 */
		if (module_load_offset == 0)
			module_load_offset =
				(get_random_int() % 1024 + 1) * PAGE_SIZE;
		mutex_unlock(&module_kaslr_mutex);
	}
	return module_load_offset;
}
#else
static unsigned long int get_module_load_offset(void)
{
	return 0;
}
#endif

void *module_alloc(unsigned long size)
{
	if (PAGE_ALIGN(size) > MODULES_LEN)
		return NULL;
	return __vmalloc_node_range(size, 1,
				    MODULES_VADDR + get_module_load_offset(),
				    MODULES_END, GFP_KERNEL | __GFP_HIGHMEM,
				    PAGE_KERNEL_EXEC, NUMA_NO_NODE,
				    __builtin_return_address(0));
}

#ifdef CONFIG_X86_32
int apply_relocate(Elf32_Shdr *sechdrs,
		   const char *strtab,
		   unsigned int symindex,
		   unsigned int relsec,
		   struct module *me)
{
	unsigned int i;
	Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
	Elf32_Sym *sym;
	uint32_t *location;

	DEBUGP("Applying relocate section %u to %u\n",
	       relsec, sechdrs[relsec].sh_info);
	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
		/* This is where to make the change */
		location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
			+ rel[i].r_offset;
		/* This is the symbol it is referring to.  Note that all
		   undefined symbols have been resolved.  */
		sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
			+ ELF32_R_SYM(rel[i].r_info);

		switch (ELF32_R_TYPE(rel[i].r_info)) {
		case R_386_32:
			/* We add the value into the location given */
			*location += sym->st_value;
			break;
		case R_386_PC32:
			/* Add the value, subtract its position */
			*location += sym->st_value - (uint32_t)location;
			break;
		default:
			pr_err("%s: Unknown relocation: %u\n",
			       me->name, ELF32_R_TYPE(rel[i].r_info));
			return -ENOEXEC;
		}
	}
	return 0;
}
#else /*X86_64*/
int apply_relocate_add(Elf64_Shdr *sechdrs,
		   const char *strtab,
		   unsigned int symindex,
		   unsigned int relsec,
		   struct module *me)
{
	unsigned int i;
	Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
	Elf64_Sym *sym;
	void *loc;
	u64 val;

	DEBUGP("Applying relocate section %u to %u\n",
	       relsec, sechdrs[relsec].sh_info);
	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
		/* This is where to make the change */
		loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
			+ rel[i].r_offset;

		/* This is the symbol it is referring to.  Note that all
		   undefined symbols have been resolved.  */
		sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
			+ ELF64_R_SYM(rel[i].r_info);

		DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
		       (int)ELF64_R_TYPE(rel[i].r_info),
		       sym->st_value, rel[i].r_addend, (u64)loc);

		val = sym->st_value + rel[i].r_addend;

		switch (ELF64_R_TYPE(rel[i].r_info)) {
		case R_X86_64_NONE:
			break;
		case R_X86_64_64:
			*(u64 *)loc = val;
			break;
		case R_X86_64_32:
			*(u32 *)loc = val;
			if (val != *(u32 *)loc)
				goto overflow;
			break;
		case R_X86_64_32S:
			*(s32 *)loc = val;
			if ((s64)val != *(s32 *)loc)
				goto overflow;
			break;
		case R_X86_64_PC32:
			val -= (u64)loc;
			*(u32 *)loc = val;
#if 0
			if ((s64)val != *(s32 *)loc)
				goto overflow;
#endif
			break;
		default:
			pr_err("%s: Unknown rela relocation: %llu\n",
			       me->name, ELF64_R_TYPE(rel[i].r_info));
			return -ENOEXEC;
		}
	}
	return 0;

overflow:
	pr_err("overflow in relocation type %d val %Lx\n",
	       (int)ELF64_R_TYPE(rel[i].r_info), val);
	pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
	       me->name);
	return -ENOEXEC;
}
#endif

int module_finalize(const Elf_Ehdr *hdr,
		    const Elf_Shdr *sechdrs,
		    struct module *me)
{
	const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
		*para = NULL;
	char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;

	for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
		if (!strcmp(".text", secstrings + s->sh_name))
			text = s;
		if (!strcmp(".altinstructions", secstrings + s->sh_name))
			alt = s;
		if (!strcmp(".smp_locks", secstrings + s->sh_name))
			locks = s;
		if (!strcmp(".parainstructions", secstrings + s->sh_name))
			para = s;
	}

	if (alt) {
		/* patch .altinstructions */
		void *aseg = (void *)alt->sh_addr;
		apply_alternatives(aseg, aseg + alt->sh_size);
	}
	if (locks && text) {
		void *lseg = (void *)locks->sh_addr;
		void *tseg = (void *)text->sh_addr;
		alternatives_smp_module_add(me, me->name,
					    lseg, lseg + locks->sh_size,
					    tseg, tseg + text->sh_size);
	}

	if (para) {
		void *pseg = (void *)para->sh_addr;
		apply_paravirt(pseg, pseg + para->sh_size);
	}

	/* make jump label nops */
	jump_label_apply_nops(me);

	return 0;
}

void module_arch_cleanup(struct module *mod)
{
	alternatives_smp_module_del(mod);
}