1 // SPDX-License-Identifier: GPL-2.0-only
2 //
3 // Copyright (C) 2019 Jason Yan <yanaijie@huawei.com>
4
5 #include <linux/kernel.h>
6 #include <linux/errno.h>
7 #include <linux/string.h>
8 #include <linux/types.h>
9 #include <linux/mm.h>
10 #include <linux/swap.h>
11 #include <linux/stddef.h>
12 #include <linux/init.h>
13 #include <linux/delay.h>
14 #include <linux/memblock.h>
15 #include <linux/libfdt.h>
16 #include <linux/crash_reserve.h>
17 #include <linux/of.h>
18 #include <linux/of_fdt.h>
19 #include <asm/cacheflush.h>
20 #include <asm/kdump.h>
21 #include <mm/mmu_decl.h>
22
23 struct regions {
24 unsigned long pa_start;
25 unsigned long pa_end;
26 unsigned long kernel_size;
27 unsigned long dtb_start;
28 unsigned long dtb_end;
29 unsigned long initrd_start;
30 unsigned long initrd_end;
31 unsigned long crash_start;
32 unsigned long crash_end;
33 int reserved_mem;
34 int reserved_mem_addr_cells;
35 int reserved_mem_size_cells;
36 };
37
38 struct regions __initdata regions;
39
40 static __init void kaslr_get_cmdline(void *fdt)
41 {
42 early_init_dt_scan_chosen(boot_command_line);
43 }
44
45 static unsigned long __init rotate_xor(unsigned long hash, const void *area,
46 size_t size)
47 {
48 size_t i;
49 const unsigned long *ptr = area;
50
51 for (i = 0; i < size / sizeof(hash); i++) {
52 /* Rotate by odd number of bits and XOR. */
53 hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7);
54 hash ^= ptr[i];
55 }
56
57 return hash;
58 }
59
60 /* Attempt to create a simple starting entropy. This can make it defferent for
61 * every build but it is still not enough. Stronger entropy should
62 * be added to make it change for every boot.
63 */
64 static unsigned long __init get_boot_seed(void *fdt)
65 {
66 unsigned long hash = 0;
67
68 /* build-specific string for starting entropy. */
69 hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
70 hash = rotate_xor(hash, fdt, fdt_totalsize(fdt));
71
72 return hash;
73 }
74
75 static __init u64 get_kaslr_seed(void *fdt)
76 {
77 int node, len;
78 fdt64_t *prop;
79 u64 ret;
80
81 node = fdt_path_offset(fdt, "/chosen");
82 if (node < 0)
83 return 0;
84
85 prop = fdt_getprop_w(fdt, node, "kaslr-seed", &len);
86 if (!prop || len != sizeof(u64))
87 return 0;
88
89 ret = fdt64_to_cpu(*prop);
90 *prop = 0;
91 return ret;
92 }
93
94 static __init bool regions_overlap(u32 s1, u32 e1, u32 s2, u32 e2)
95 {
96 return e1 >= s2 && e2 >= s1;
97 }
98
99 static __init bool overlaps_reserved_region(const void *fdt, u32 start,
100 u32 end)
101 {
102 int subnode, len, i;
103 u64 base, size;
104
105 /* check for overlap with /memreserve/ entries */
106 for (i = 0; i < fdt_num_mem_rsv(fdt); i++) {
107 if (fdt_get_mem_rsv(fdt, i, &base, &size) < 0)
108 continue;
109 if (regions_overlap(start, end, base, base + size))
110 return true;
111 }
112
113 if (regions.reserved_mem < 0)
114 return false;
115
116 /* check for overlap with static reservations in /reserved-memory */
117 for (subnode = fdt_first_subnode(fdt, regions.reserved_mem);
118 subnode >= 0;
119 subnode = fdt_next_subnode(fdt, subnode)) {
120 const fdt32_t *reg;
121 u64 rsv_end;
122
123 len = 0;
124 reg = fdt_getprop(fdt, subnode, "reg", &len);
125 while (len >= (regions.reserved_mem_addr_cells +
126 regions.reserved_mem_size_cells)) {
127 base = fdt32_to_cpu(reg[0]);
128 if (regions.reserved_mem_addr_cells == 2)
129 base = (base << 32) | fdt32_to_cpu(reg[1]);
130
131 reg += regions.reserved_mem_addr_cells;
132 len -= 4 * regions.reserved_mem_addr_cells;
133
134 size = fdt32_to_cpu(reg[0]);
135 if (regions.reserved_mem_size_cells == 2)
136 size = (size << 32) | fdt32_to_cpu(reg[1]);
137
138 reg += regions.reserved_mem_size_cells;
139 len -= 4 * regions.reserved_mem_size_cells;
140
141 if (base >= regions.pa_end)
142 continue;
143
144 rsv_end = min(base + size, (u64)U32_MAX);
145
146 if (regions_overlap(start, end, base, rsv_end))
147 return true;
148 }
149 }
150 return false;
151 }
152
153 static __init bool overlaps_region(const void *fdt, u32 start,
154 u32 end)
155 {
156 if (regions_overlap(start, end, __pa(_stext), __pa(_end)))
157 return true;
158
159 if (regions_overlap(start, end, regions.dtb_start,
160 regions.dtb_end))
161 return true;
162
163 if (regions_overlap(start, end, regions.initrd_start,
164 regions.initrd_end))
165 return true;
166
167 if (regions_overlap(start, end, regions.crash_start,
168 regions.crash_end))
169 return true;
170
171 return overlaps_reserved_region(fdt, start, end);
172 }
173
174 static void __init get_crash_kernel(void *fdt, unsigned long size)
175 {
176 #ifdef CONFIG_CRASH_RESERVE
177 unsigned long long crash_size, crash_base;
178 int ret;
179
180 ret = parse_crashkernel(boot_command_line, size, &crash_size,
181 &crash_base, NULL, NULL);
182 if (ret != 0 || crash_size == 0)
183 return;
184 if (crash_base == 0)
185 crash_base = KDUMP_KERNELBASE;
186
187 regions.crash_start = (unsigned long)crash_base;
188 regions.crash_end = (unsigned long)(crash_base + crash_size);
189
190 pr_debug("crash_base=0x%llx crash_size=0x%llx\n", crash_base, crash_size);
191 #endif
192 }
193
194 static void __init get_initrd_range(void *fdt)
195 {
196 u64 start, end;
197 int node, len;
198 const __be32 *prop;
199
200 node = fdt_path_offset(fdt, "/chosen");
201 if (node < 0)
202 return;
203
204 prop = fdt_getprop(fdt, node, "linux,initrd-start", &len);
205 if (!prop)
206 return;
207 start = of_read_number(prop, len / 4);
208
209 prop = fdt_getprop(fdt, node, "linux,initrd-end", &len);
210 if (!prop)
211 return;
212 end = of_read_number(prop, len / 4);
213
214 regions.initrd_start = (unsigned long)start;
215 regions.initrd_end = (unsigned long)end;
216
217 pr_debug("initrd_start=0x%llx initrd_end=0x%llx\n", start, end);
218 }
219
220 static __init unsigned long get_usable_address(const void *fdt,
221 unsigned long start,
222 unsigned long offset)
223 {
224 unsigned long pa;
225 unsigned long pa_end;
226
227 for (pa = offset; (long)pa > (long)start; pa -= SZ_16K) {
228 pa_end = pa + regions.kernel_size;
229 if (overlaps_region(fdt, pa, pa_end))
230 continue;
231
232 return pa;
233 }
234 return 0;
235 }
236
237 static __init void get_cell_sizes(const void *fdt, int node, int *addr_cells,
238 int *size_cells)
239 {
240 const int *prop;
241 int len;
242
243 /*
244 * Retrieve the #address-cells and #size-cells properties
245 * from the 'node', or use the default if not provided.
246 */
247 *addr_cells = *size_cells = 1;
248
249 prop = fdt_getprop(fdt, node, "#address-cells", &len);
250 if (len == 4)
251 *addr_cells = fdt32_to_cpu(*prop);
252 prop = fdt_getprop(fdt, node, "#size-cells", &len);
253 if (len == 4)
254 *size_cells = fdt32_to_cpu(*prop);
255 }
256
257 static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long index,
258 unsigned long offset)
259 {
260 unsigned long koffset = 0;
261 unsigned long start;
262
263 while ((long)index >= 0) {
264 offset = memstart_addr + index * SZ_64M + offset;
265 start = memstart_addr + index * SZ_64M;
266 koffset = get_usable_address(dt_ptr, start, offset);
267 if (koffset)
268 break;
269 index--;
270 }
271
272 if (koffset != 0)
273 koffset -= memstart_addr;
274
275 return koffset;
276 }
277
278 static inline __init bool kaslr_disabled(void)
279 {
280 return strstr(boot_command_line, "nokaslr") != NULL;
281 }
282
283 static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size,
284 unsigned long kernel_sz)
285 {
286 unsigned long offset, random;
287 unsigned long ram, linear_sz;
288 u64 seed;
289 unsigned long index;
290
291 kaslr_get_cmdline(dt_ptr);
292 if (kaslr_disabled())
293 return 0;
294
295 random = get_boot_seed(dt_ptr);
296
297 seed = get_tb() << 32;
298 seed ^= get_tb();
299 random = rotate_xor(random, &seed, sizeof(seed));
300
301 /*
302 * Retrieve (and wipe) the seed from the FDT
303 */
304 seed = get_kaslr_seed(dt_ptr);
305 if (seed)
306 random = rotate_xor(random, &seed, sizeof(seed));
307 else
308 pr_warn("KASLR: No safe seed for randomizing the kernel base.\n");
309
310 ram = min_t(phys_addr_t, __max_low_memory, size);
311 ram = map_mem_in_cams(ram, CONFIG_LOWMEM_CAM_NUM, true, true);
312 linear_sz = min_t(unsigned long, ram, SZ_512M);
313
314 /* If the linear size is smaller than 64M, do not randomize */
315 if (linear_sz < SZ_64M)
316 return 0;
317
318 /* check for a reserved-memory node and record its cell sizes */
319 regions.reserved_mem = fdt_path_offset(dt_ptr, "/reserved-memory");
320 if (regions.reserved_mem >= 0)
321 get_cell_sizes(dt_ptr, regions.reserved_mem,
322 ®ions.reserved_mem_addr_cells,
323 ®ions.reserved_mem_size_cells);
324
325 regions.pa_start = memstart_addr;
326 regions.pa_end = memstart_addr + linear_sz;
327 regions.dtb_start = __pa(dt_ptr);
328 regions.dtb_end = __pa(dt_ptr) + fdt_totalsize(dt_ptr);
329 regions.kernel_size = kernel_sz;
330
331 get_initrd_range(dt_ptr);
332 get_crash_kernel(dt_ptr, ram);
333
334 /*
335 * Decide which 64M we want to start
336 * Only use the low 8 bits of the random seed
337 */
338 index = random & 0xFF;
339 index %= linear_sz / SZ_64M;
340
341 /* Decide offset inside 64M */
342 offset = random % (SZ_64M - kernel_sz);
343 offset = round_down(offset, SZ_16K);
344
345 return kaslr_legal_offset(dt_ptr, index, offset);
346 }
347
348 /*
349 * To see if we need to relocate the kernel to a random offset
350 * void *dt_ptr - address of the device tree
351 * phys_addr_t size - size of the first memory block
352 */
353 notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
354 {
355 unsigned long tlb_virt;
356 phys_addr_t tlb_phys;
357 unsigned long offset;
358 unsigned long kernel_sz;
359
360 kernel_sz = (unsigned long)_end - (unsigned long)_stext;
361
362 offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
363 if (offset == 0)
364 return;
365
366 kernstart_virt_addr += offset;
367 kernstart_addr += offset;
368
369 is_second_reloc = 1;
370
371 if (offset >= SZ_64M) {
372 tlb_virt = round_down(kernstart_virt_addr, SZ_64M);
373 tlb_phys = round_down(kernstart_addr, SZ_64M);
374
375 /* Create kernel map to relocate in */
376 create_kaslr_tlb_entry(1, tlb_virt, tlb_phys);
377 }
378
379 /* Copy the kernel to its new location and run */
380 memcpy((void *)kernstart_virt_addr, (void *)_stext, kernel_sz);
381 flush_icache_range(kernstart_virt_addr, kernstart_virt_addr + kernel_sz);
382
383 reloc_kernel_entry(dt_ptr, kernstart_virt_addr);
384 }
385
386 void __init kaslr_late_init(void)
387 {
388 /* If randomized, clear the original kernel */
389 if (kernstart_virt_addr != KERNELBASE) {
390 unsigned long kernel_sz;
391
392 kernel_sz = (unsigned long)_end - kernstart_virt_addr;
393 memzero_explicit((void *)KERNELBASE, kernel_sz);
394 }
395 }
396
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