summaryrefslogtreecommitdiff
path: root/arch/loongarch/kernel/relocate.c
blob: 1acfa704c8d09b95b625da9fd047833b181d35f7 (plain)
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
// SPDX-License-Identifier: GPL-2.0
/*
 * Support for Kernel relocation at boot time
 *
 * Copyright (C) 2023 Loongson Technology Corporation Limited
 */

#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/printk.h>
#include <linux/panic_notifier.h>
#include <linux/start_kernel.h>
#include <asm/bootinfo.h>
#include <asm/early_ioremap.h>
#include <asm/inst.h>
#include <asm/sections.h>
#include <asm/setup.h>

#define RELOCATED(x) ((void *)((long)x + reloc_offset))
#define RELOCATED_KASLR(x) ((void *)((long)x + random_offset))

static unsigned long reloc_offset;

static inline void __init relocate_relative(void)
{
	Elf64_Rela *rela, *rela_end;
	rela = (Elf64_Rela *)&__rela_dyn_begin;
	rela_end = (Elf64_Rela *)&__rela_dyn_end;

	for ( ; rela < rela_end; rela++) {
		Elf64_Addr addr = rela->r_offset;
		Elf64_Addr relocated_addr = rela->r_addend;

		if (rela->r_info != R_LARCH_RELATIVE)
			continue;

		if (relocated_addr >= VMLINUX_LOAD_ADDRESS)
			relocated_addr = (Elf64_Addr)RELOCATED(relocated_addr);

		*(Elf64_Addr *)RELOCATED(addr) = relocated_addr;
	}
}

static inline void __init relocate_absolute(long random_offset)
{
	void *begin, *end;
	struct rela_la_abs *p;

	begin = RELOCATED_KASLR(&__la_abs_begin);
	end   = RELOCATED_KASLR(&__la_abs_end);

	for (p = begin; (void *)p < end; p++) {
		long v = p->symvalue;
		uint32_t lu12iw, ori, lu32id, lu52id;
		union loongarch_instruction *insn = (void *)p->pc;

		lu12iw = (v >> 12) & 0xfffff;
		ori    = v & 0xfff;
		lu32id = (v >> 32) & 0xfffff;
		lu52id = v >> 52;

		insn[0].reg1i20_format.immediate = lu12iw;
		insn[1].reg2i12_format.immediate = ori;
		insn[2].reg1i20_format.immediate = lu32id;
		insn[3].reg2i12_format.immediate = lu52id;
	}
}

#ifdef CONFIG_RANDOMIZE_BASE
static inline __init unsigned long rotate_xor(unsigned long hash,
					      const void *area, size_t size)
{
	size_t i, diff;
	const typeof(hash) *ptr = PTR_ALIGN(area, sizeof(hash));

	diff = (void *)ptr - area;
	if (size < diff + sizeof(hash))
		return hash;

	size = ALIGN_DOWN(size - diff, sizeof(hash));

	for (i = 0; i < size / sizeof(hash); i++) {
		/* Rotate by odd number of bits and XOR. */
		hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7);
		hash ^= ptr[i];
	}

	return hash;
}

static inline __init unsigned long get_random_boot(void)
{
	unsigned long hash = 0;
	unsigned long entropy = random_get_entropy();

	/* Attempt to create a simple but unpredictable starting entropy. */
	hash = rotate_xor(hash, linux_banner, strlen(linux_banner));

	/* Add in any runtime entropy we can get */
	hash = rotate_xor(hash, &entropy, sizeof(entropy));

	return hash;
}

static int __init nokaslr(char *p)
{
	pr_info("KASLR is disabled.\n");

	return 0; /* Print a notice and silence the boot warning */
}
early_param("nokaslr", nokaslr);

static inline __init bool kaslr_disabled(void)
{
	char *str;
	const char *builtin_cmdline = CONFIG_CMDLINE;

	str = strstr(builtin_cmdline, "nokaslr");
	if (str == builtin_cmdline || (str > builtin_cmdline && *(str - 1) == ' '))
		return true;

	str = strstr(boot_command_line, "nokaslr");
	if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' '))
		return true;

	return false;
}

/* Choose a new address for the kernel */
static inline void __init *determine_relocation_address(void)
{
	unsigned long kernel_length;
	unsigned long random_offset;
	void *destination = _text;

	if (kaslr_disabled())
		return destination;

	kernel_length = (long)_end - (long)_text;

	random_offset = get_random_boot() << 16;
	random_offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
	if (random_offset < kernel_length)
		random_offset += ALIGN(kernel_length, 0xffff);

	return RELOCATED_KASLR(destination);
}

static inline int __init relocation_addr_valid(void *location_new)
{
	if ((unsigned long)location_new & 0x00000ffff)
		return 0; /* Inappropriately aligned new location */

	if ((unsigned long)location_new < (unsigned long)_end)
		return 0; /* New location overlaps original kernel */

	return 1;
}
#endif

static inline void __init update_reloc_offset(unsigned long *addr, long random_offset)
{
	unsigned long *new_addr = (unsigned long *)RELOCATED_KASLR(addr);

	*new_addr = (unsigned long)reloc_offset;
}

unsigned long __init relocate_kernel(void)
{
	unsigned long kernel_length;
	unsigned long random_offset = 0;
	void *location_new = _text; /* Default to original kernel start */
	char *cmdline = early_ioremap(fw_arg1, COMMAND_LINE_SIZE); /* Boot command line is passed in fw_arg1 */

	strscpy(boot_command_line, cmdline, COMMAND_LINE_SIZE);

#ifdef CONFIG_RANDOMIZE_BASE
	location_new = determine_relocation_address();

	/* Sanity check relocation address */
	if (relocation_addr_valid(location_new))
		random_offset = (unsigned long)location_new - (unsigned long)(_text);
#endif
	reloc_offset = (unsigned long)_text - VMLINUX_LOAD_ADDRESS;

	if (random_offset) {
		kernel_length = (long)(_end) - (long)(_text);

		/* Copy the kernel to it's new location */
		memcpy(location_new, _text, kernel_length);

		/* Sync the caches ready for execution of new kernel */
		__asm__ __volatile__ (
			"ibar 0 \t\n"
			"dbar 0 \t\n"
			::: "memory");

		reloc_offset += random_offset;

		/* The current thread is now within the relocated kernel */
		__current_thread_info = RELOCATED_KASLR(__current_thread_info);

		update_reloc_offset(&reloc_offset, random_offset);
	}

	if (reloc_offset)
		relocate_relative();

	relocate_absolute(random_offset);

	return random_offset;
}

/*
 * Show relocation information on panic.
 */
static void show_kernel_relocation(const char *level)
{
	if (reloc_offset > 0) {
		printk(level);
		pr_cont("Kernel relocated by 0x%lx\n", reloc_offset);
		pr_cont(" .text @ 0x%px\n", _text);
		pr_cont(" .data @ 0x%px\n", _sdata);
		pr_cont(" .bss  @ 0x%px\n", __bss_start);
	}
}

static int kernel_location_notifier_fn(struct notifier_block *self,
				       unsigned long v, void *p)
{
	show_kernel_relocation(KERN_EMERG);
	return NOTIFY_DONE;
}

static struct notifier_block kernel_location_notifier = {
	.notifier_call = kernel_location_notifier_fn
};

static int __init register_kernel_offset_dumper(void)
{
	atomic_notifier_chain_register(&panic_notifier_list,
				       &kernel_location_notifier);
	return 0;
}

arch_initcall(register_kernel_offset_dumper);