summaryrefslogtreecommitdiff
path: root/arch/powerpc/mm/nohash/kaslr_booke.c
blob: b4f2786a7d2b0be0ad3f064a89d79aad68999bdd (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
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
// SPDX-License-Identifier: GPL-2.0-only
//
// Copyright (C) 2019 Jason Yan <yanaijie@huawei.com>

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/stddef.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/memblock.h>
#include <linux/libfdt.h>
#include <linux/crash_core.h>
#include <linux/of.h>
#include <linux/of_fdt.h>
#include <asm/cacheflush.h>
#include <asm/kdump.h>
#include <mm/mmu_decl.h>

struct regions {
	unsigned long pa_start;
	unsigned long pa_end;
	unsigned long kernel_size;
	unsigned long dtb_start;
	unsigned long dtb_end;
	unsigned long initrd_start;
	unsigned long initrd_end;
	unsigned long crash_start;
	unsigned long crash_end;
	int reserved_mem;
	int reserved_mem_addr_cells;
	int reserved_mem_size_cells;
};

struct regions __initdata regions;

static __init void kaslr_get_cmdline(void *fdt)
{
	early_init_dt_scan_chosen(boot_command_line);
}

static unsigned long __init rotate_xor(unsigned long hash, const void *area,
				       size_t size)
{
	size_t i;
	const unsigned long *ptr = area;

	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;
}

/* Attempt to create a simple starting entropy. This can make it defferent for
 * every build but it is still not enough. Stronger entropy should
 * be added to make it change for every boot.
 */
static unsigned long __init get_boot_seed(void *fdt)
{
	unsigned long hash = 0;

	/* build-specific string for starting entropy. */
	hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
	hash = rotate_xor(hash, fdt, fdt_totalsize(fdt));

	return hash;
}

static __init u64 get_kaslr_seed(void *fdt)
{
	int node, len;
	fdt64_t *prop;
	u64 ret;

	node = fdt_path_offset(fdt, "/chosen");
	if (node < 0)
		return 0;

	prop = fdt_getprop_w(fdt, node, "kaslr-seed", &len);
	if (!prop || len != sizeof(u64))
		return 0;

	ret = fdt64_to_cpu(*prop);
	*prop = 0;
	return ret;
}

static __init bool regions_overlap(u32 s1, u32 e1, u32 s2, u32 e2)
{
	return e1 >= s2 && e2 >= s1;
}

static __init bool overlaps_reserved_region(const void *fdt, u32 start,
					    u32 end)
{
	int subnode, len, i;
	u64 base, size;

	/* check for overlap with /memreserve/ entries */
	for (i = 0; i < fdt_num_mem_rsv(fdt); i++) {
		if (fdt_get_mem_rsv(fdt, i, &base, &size) < 0)
			continue;
		if (regions_overlap(start, end, base, base + size))
			return true;
	}

	if (regions.reserved_mem < 0)
		return false;

	/* check for overlap with static reservations in /reserved-memory */
	for (subnode = fdt_first_subnode(fdt, regions.reserved_mem);
	     subnode >= 0;
	     subnode = fdt_next_subnode(fdt, subnode)) {
		const fdt32_t *reg;
		u64 rsv_end;

		len = 0;
		reg = fdt_getprop(fdt, subnode, "reg", &len);
		while (len >= (regions.reserved_mem_addr_cells +
			       regions.reserved_mem_size_cells)) {
			base = fdt32_to_cpu(reg[0]);
			if (regions.reserved_mem_addr_cells == 2)
				base = (base << 32) | fdt32_to_cpu(reg[1]);

			reg += regions.reserved_mem_addr_cells;
			len -= 4 * regions.reserved_mem_addr_cells;

			size = fdt32_to_cpu(reg[0]);
			if (regions.reserved_mem_size_cells == 2)
				size = (size << 32) | fdt32_to_cpu(reg[1]);

			reg += regions.reserved_mem_size_cells;
			len -= 4 * regions.reserved_mem_size_cells;

			if (base >= regions.pa_end)
				continue;

			rsv_end = min(base + size, (u64)U32_MAX);

			if (regions_overlap(start, end, base, rsv_end))
				return true;
		}
	}
	return false;
}

static __init bool overlaps_region(const void *fdt, u32 start,
				   u32 end)
{
	if (regions_overlap(start, end, __pa(_stext), __pa(_end)))
		return true;

	if (regions_overlap(start, end, regions.dtb_start,
			    regions.dtb_end))
		return true;

	if (regions_overlap(start, end, regions.initrd_start,
			    regions.initrd_end))
		return true;

	if (regions_overlap(start, end, regions.crash_start,
			    regions.crash_end))
		return true;

	return overlaps_reserved_region(fdt, start, end);
}

static void __init get_crash_kernel(void *fdt, unsigned long size)
{
#ifdef CONFIG_CRASH_CORE
	unsigned long long crash_size, crash_base;
	int ret;

	ret = parse_crashkernel(boot_command_line, size, &crash_size,
				&crash_base, NULL, NULL);
	if (ret != 0 || crash_size == 0)
		return;
	if (crash_base == 0)
		crash_base = KDUMP_KERNELBASE;

	regions.crash_start = (unsigned long)crash_base;
	regions.crash_end = (unsigned long)(crash_base + crash_size);

	pr_debug("crash_base=0x%llx crash_size=0x%llx\n", crash_base, crash_size);
#endif
}

static void __init get_initrd_range(void *fdt)
{
	u64 start, end;
	int node, len;
	const __be32 *prop;

	node = fdt_path_offset(fdt, "/chosen");
	if (node < 0)
		return;

	prop = fdt_getprop(fdt, node, "linux,initrd-start", &len);
	if (!prop)
		return;
	start = of_read_number(prop, len / 4);

	prop = fdt_getprop(fdt, node, "linux,initrd-end", &len);
	if (!prop)
		return;
	end = of_read_number(prop, len / 4);

	regions.initrd_start = (unsigned long)start;
	regions.initrd_end = (unsigned long)end;

	pr_debug("initrd_start=0x%llx  initrd_end=0x%llx\n", start, end);
}

static __init unsigned long get_usable_address(const void *fdt,
					       unsigned long start,
					       unsigned long offset)
{
	unsigned long pa;
	unsigned long pa_end;

	for (pa = offset; (long)pa > (long)start; pa -= SZ_16K) {
		pa_end = pa + regions.kernel_size;
		if (overlaps_region(fdt, pa, pa_end))
			continue;

		return pa;
	}
	return 0;
}

static __init void get_cell_sizes(const void *fdt, int node, int *addr_cells,
				  int *size_cells)
{
	const int *prop;
	int len;

	/*
	 * Retrieve the #address-cells and #size-cells properties
	 * from the 'node', or use the default if not provided.
	 */
	*addr_cells = *size_cells = 1;

	prop = fdt_getprop(fdt, node, "#address-cells", &len);
	if (len == 4)
		*addr_cells = fdt32_to_cpu(*prop);
	prop = fdt_getprop(fdt, node, "#size-cells", &len);
	if (len == 4)
		*size_cells = fdt32_to_cpu(*prop);
}

static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long index,
					       unsigned long offset)
{
	unsigned long koffset = 0;
	unsigned long start;

	while ((long)index >= 0) {
		offset = memstart_addr + index * SZ_64M + offset;
		start = memstart_addr + index * SZ_64M;
		koffset = get_usable_address(dt_ptr, start, offset);
		if (koffset)
			break;
		index--;
	}

	if (koffset != 0)
		koffset -= memstart_addr;

	return koffset;
}

static inline __init bool kaslr_disabled(void)
{
	return strstr(boot_command_line, "nokaslr") != NULL;
}

static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size,
						  unsigned long kernel_sz)
{
	unsigned long offset, random;
	unsigned long ram, linear_sz;
	u64 seed;
	unsigned long index;

	kaslr_get_cmdline(dt_ptr);
	if (kaslr_disabled())
		return 0;

	random = get_boot_seed(dt_ptr);

	seed = get_tb() << 32;
	seed ^= get_tb();
	random = rotate_xor(random, &seed, sizeof(seed));

	/*
	 * Retrieve (and wipe) the seed from the FDT
	 */
	seed = get_kaslr_seed(dt_ptr);
	if (seed)
		random = rotate_xor(random, &seed, sizeof(seed));
	else
		pr_warn("KASLR: No safe seed for randomizing the kernel base.\n");

	ram = min_t(phys_addr_t, __max_low_memory, size);
	ram = map_mem_in_cams(ram, CONFIG_LOWMEM_CAM_NUM, true, true);
	linear_sz = min_t(unsigned long, ram, SZ_512M);

	/* If the linear size is smaller than 64M, do not randomize */
	if (linear_sz < SZ_64M)
		return 0;

	/* check for a reserved-memory node and record its cell sizes */
	regions.reserved_mem = fdt_path_offset(dt_ptr, "/reserved-memory");
	if (regions.reserved_mem >= 0)
		get_cell_sizes(dt_ptr, regions.reserved_mem,
			       &regions.reserved_mem_addr_cells,
			       &regions.reserved_mem_size_cells);

	regions.pa_start = memstart_addr;
	regions.pa_end = memstart_addr + linear_sz;
	regions.dtb_start = __pa(dt_ptr);
	regions.dtb_end = __pa(dt_ptr) + fdt_totalsize(dt_ptr);
	regions.kernel_size = kernel_sz;

	get_initrd_range(dt_ptr);
	get_crash_kernel(dt_ptr, ram);

	/*
	 * Decide which 64M we want to start
	 * Only use the low 8 bits of the random seed
	 */
	index = random & 0xFF;
	index %= linear_sz / SZ_64M;

	/* Decide offset inside 64M */
	offset = random % (SZ_64M - kernel_sz);
	offset = round_down(offset, SZ_16K);

	return kaslr_legal_offset(dt_ptr, index, offset);
}

/*
 * To see if we need to relocate the kernel to a random offset
 * void *dt_ptr - address of the device tree
 * phys_addr_t size - size of the first memory block
 */
notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
{
	unsigned long tlb_virt;
	phys_addr_t tlb_phys;
	unsigned long offset;
	unsigned long kernel_sz;

	kernel_sz = (unsigned long)_end - (unsigned long)_stext;

	offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
	if (offset == 0)
		return;

	kernstart_virt_addr += offset;
	kernstart_addr += offset;

	is_second_reloc = 1;

	if (offset >= SZ_64M) {
		tlb_virt = round_down(kernstart_virt_addr, SZ_64M);
		tlb_phys = round_down(kernstart_addr, SZ_64M);

		/* Create kernel map to relocate in */
		create_kaslr_tlb_entry(1, tlb_virt, tlb_phys);
	}

	/* Copy the kernel to it's new location and run */
	memcpy((void *)kernstart_virt_addr, (void *)_stext, kernel_sz);
	flush_icache_range(kernstart_virt_addr, kernstart_virt_addr + kernel_sz);

	reloc_kernel_entry(dt_ptr, kernstart_virt_addr);
}

void __init kaslr_late_init(void)
{
	/* If randomized, clear the original kernel */
	if (kernstart_virt_addr != KERNELBASE) {
		unsigned long kernel_sz;

		kernel_sz = (unsigned long)_end - kernstart_virt_addr;
		memzero_explicit((void *)KERNELBASE, kernel_sz);
	}
}