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8ab3820f KC |
1 | #include "misc.h" |
2 | ||
5bfce5ef KC |
3 | #include <asm/msr.h> |
4 | #include <asm/archrandom.h> | |
82fa9637 | 5 | #include <asm/e820.h> |
5bfce5ef | 6 | |
a653f356 KC |
7 | #include <generated/compile.h> |
8 | #include <linux/module.h> | |
9 | #include <linux/uts.h> | |
10 | #include <linux/utsname.h> | |
11 | #include <generated/utsrelease.h> | |
a653f356 KC |
12 | |
13 | /* Simplified build-specific string for starting entropy. */ | |
327f7d72 | 14 | static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@" |
a653f356 KC |
15 | LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION; |
16 | ||
5bfce5ef KC |
17 | #define I8254_PORT_CONTROL 0x43 |
18 | #define I8254_PORT_COUNTER0 0x40 | |
19 | #define I8254_CMD_READBACK 0xC0 | |
20 | #define I8254_SELECT_COUNTER0 0x02 | |
21 | #define I8254_STATUS_NOTREADY 0x40 | |
22 | static inline u16 i8254(void) | |
23 | { | |
24 | u16 status, timer; | |
25 | ||
26 | do { | |
27 | outb(I8254_PORT_CONTROL, | |
28 | I8254_CMD_READBACK | I8254_SELECT_COUNTER0); | |
29 | status = inb(I8254_PORT_COUNTER0); | |
30 | timer = inb(I8254_PORT_COUNTER0); | |
31 | timer |= inb(I8254_PORT_COUNTER0) << 8; | |
32 | } while (status & I8254_STATUS_NOTREADY); | |
33 | ||
34 | return timer; | |
35 | } | |
36 | ||
a653f356 KC |
37 | static unsigned long rotate_xor(unsigned long hash, const void *area, |
38 | size_t size) | |
39 | { | |
40 | size_t i; | |
41 | unsigned long *ptr = (unsigned long *)area; | |
42 | ||
43 | for (i = 0; i < size / sizeof(hash); i++) { | |
44 | /* Rotate by odd number of bits and XOR. */ | |
45 | hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7); | |
46 | hash ^= ptr[i]; | |
47 | } | |
48 | ||
49 | return hash; | |
50 | } | |
51 | ||
52 | /* Attempt to create a simple but unpredictable starting entropy. */ | |
53 | static unsigned long get_random_boot(void) | |
54 | { | |
55 | unsigned long hash = 0; | |
56 | ||
57 | hash = rotate_xor(hash, build_str, sizeof(build_str)); | |
58 | hash = rotate_xor(hash, real_mode, sizeof(*real_mode)); | |
59 | ||
60 | return hash; | |
61 | } | |
62 | ||
5bfce5ef KC |
63 | static unsigned long get_random_long(void) |
64 | { | |
e8236c4d PA |
65 | #ifdef CONFIG_X86_64 |
66 | const unsigned long mix_const = 0x5d6008cbf3848dd3UL; | |
67 | #else | |
68 | const unsigned long mix_const = 0x3f39e593UL; | |
69 | #endif | |
a653f356 KC |
70 | unsigned long raw, random = get_random_boot(); |
71 | bool use_i8254 = true; | |
72 | ||
73 | debug_putstr("KASLR using"); | |
5bfce5ef KC |
74 | |
75 | if (has_cpuflag(X86_FEATURE_RDRAND)) { | |
a653f356 KC |
76 | debug_putstr(" RDRAND"); |
77 | if (rdrand_long(&raw)) { | |
78 | random ^= raw; | |
79 | use_i8254 = false; | |
80 | } | |
5bfce5ef KC |
81 | } |
82 | ||
83 | if (has_cpuflag(X86_FEATURE_TSC)) { | |
a653f356 | 84 | debug_putstr(" RDTSC"); |
4ea1636b | 85 | raw = rdtsc(); |
5bfce5ef | 86 | |
a653f356 KC |
87 | random ^= raw; |
88 | use_i8254 = false; | |
89 | } | |
5bfce5ef | 90 | |
a653f356 KC |
91 | if (use_i8254) { |
92 | debug_putstr(" i8254"); | |
93 | random ^= i8254(); | |
5bfce5ef KC |
94 | } |
95 | ||
e8236c4d PA |
96 | /* Circular multiply for better bit diffusion */ |
97 | asm("mul %3" | |
98 | : "=a" (random), "=d" (raw) | |
99 | : "a" (random), "rm" (mix_const)); | |
100 | random += raw; | |
101 | ||
a653f356 KC |
102 | debug_putstr("...\n"); |
103 | ||
5bfce5ef KC |
104 | return random; |
105 | } | |
8ab3820f | 106 | |
82fa9637 KC |
107 | struct mem_vector { |
108 | unsigned long start; | |
109 | unsigned long size; | |
110 | }; | |
111 | ||
112 | #define MEM_AVOID_MAX 5 | |
e290e8c5 | 113 | static struct mem_vector mem_avoid[MEM_AVOID_MAX]; |
82fa9637 KC |
114 | |
115 | static bool mem_contains(struct mem_vector *region, struct mem_vector *item) | |
116 | { | |
117 | /* Item at least partially before region. */ | |
118 | if (item->start < region->start) | |
119 | return false; | |
120 | /* Item at least partially after region. */ | |
121 | if (item->start + item->size > region->start + region->size) | |
122 | return false; | |
123 | return true; | |
124 | } | |
125 | ||
126 | static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two) | |
127 | { | |
128 | /* Item one is entirely before item two. */ | |
129 | if (one->start + one->size <= two->start) | |
130 | return false; | |
131 | /* Item one is entirely after item two. */ | |
132 | if (one->start >= two->start + two->size) | |
133 | return false; | |
134 | return true; | |
135 | } | |
136 | ||
137 | static void mem_avoid_init(unsigned long input, unsigned long input_size, | |
138 | unsigned long output, unsigned long output_size) | |
139 | { | |
140 | u64 initrd_start, initrd_size; | |
141 | u64 cmd_line, cmd_line_size; | |
142 | unsigned long unsafe, unsafe_len; | |
143 | char *ptr; | |
144 | ||
145 | /* | |
146 | * Avoid the region that is unsafe to overlap during | |
147 | * decompression (see calculations at top of misc.c). | |
148 | */ | |
149 | unsafe_len = (output_size >> 12) + 32768 + 18; | |
150 | unsafe = (unsigned long)input + input_size - unsafe_len; | |
151 | mem_avoid[0].start = unsafe; | |
152 | mem_avoid[0].size = unsafe_len; | |
153 | ||
154 | /* Avoid initrd. */ | |
155 | initrd_start = (u64)real_mode->ext_ramdisk_image << 32; | |
156 | initrd_start |= real_mode->hdr.ramdisk_image; | |
157 | initrd_size = (u64)real_mode->ext_ramdisk_size << 32; | |
158 | initrd_size |= real_mode->hdr.ramdisk_size; | |
159 | mem_avoid[1].start = initrd_start; | |
160 | mem_avoid[1].size = initrd_size; | |
161 | ||
162 | /* Avoid kernel command line. */ | |
163 | cmd_line = (u64)real_mode->ext_cmd_line_ptr << 32; | |
164 | cmd_line |= real_mode->hdr.cmd_line_ptr; | |
165 | /* Calculate size of cmd_line. */ | |
166 | ptr = (char *)(unsigned long)cmd_line; | |
167 | for (cmd_line_size = 0; ptr[cmd_line_size++]; ) | |
168 | ; | |
169 | mem_avoid[2].start = cmd_line; | |
170 | mem_avoid[2].size = cmd_line_size; | |
171 | ||
172 | /* Avoid heap memory. */ | |
173 | mem_avoid[3].start = (unsigned long)free_mem_ptr; | |
174 | mem_avoid[3].size = BOOT_HEAP_SIZE; | |
175 | ||
176 | /* Avoid stack memory. */ | |
177 | mem_avoid[4].start = (unsigned long)free_mem_end_ptr; | |
178 | mem_avoid[4].size = BOOT_STACK_SIZE; | |
179 | } | |
180 | ||
181 | /* Does this memory vector overlap a known avoided area? */ | |
e290e8c5 | 182 | static bool mem_avoid_overlap(struct mem_vector *img) |
82fa9637 KC |
183 | { |
184 | int i; | |
0cacbfbe | 185 | struct setup_data *ptr; |
82fa9637 KC |
186 | |
187 | for (i = 0; i < MEM_AVOID_MAX; i++) { | |
188 | if (mem_overlaps(img, &mem_avoid[i])) | |
189 | return true; | |
190 | } | |
191 | ||
0cacbfbe KC |
192 | /* Avoid all entries in the setup_data linked list. */ |
193 | ptr = (struct setup_data *)(unsigned long)real_mode->hdr.setup_data; | |
194 | while (ptr) { | |
195 | struct mem_vector avoid; | |
196 | ||
20cc2888 | 197 | avoid.start = (unsigned long)ptr; |
0cacbfbe KC |
198 | avoid.size = sizeof(*ptr) + ptr->len; |
199 | ||
200 | if (mem_overlaps(img, &avoid)) | |
201 | return true; | |
202 | ||
203 | ptr = (struct setup_data *)(unsigned long)ptr->next; | |
204 | } | |
205 | ||
82fa9637 KC |
206 | return false; |
207 | } | |
208 | ||
e290e8c5 KC |
209 | static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET / |
210 | CONFIG_PHYSICAL_ALIGN]; | |
211 | static unsigned long slot_max; | |
82fa9637 KC |
212 | |
213 | static void slots_append(unsigned long addr) | |
214 | { | |
215 | /* Overflowing the slots list should be impossible. */ | |
216 | if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET / | |
217 | CONFIG_PHYSICAL_ALIGN) | |
218 | return; | |
219 | ||
220 | slots[slot_max++] = addr; | |
221 | } | |
222 | ||
223 | static unsigned long slots_fetch_random(void) | |
224 | { | |
225 | /* Handle case of no slots stored. */ | |
226 | if (slot_max == 0) | |
227 | return 0; | |
228 | ||
229 | return slots[get_random_long() % slot_max]; | |
230 | } | |
231 | ||
232 | static void process_e820_entry(struct e820entry *entry, | |
233 | unsigned long minimum, | |
234 | unsigned long image_size) | |
235 | { | |
236 | struct mem_vector region, img; | |
237 | ||
238 | /* Skip non-RAM entries. */ | |
239 | if (entry->type != E820_RAM) | |
240 | return; | |
241 | ||
242 | /* Ignore entries entirely above our maximum. */ | |
243 | if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET) | |
244 | return; | |
245 | ||
246 | /* Ignore entries entirely below our minimum. */ | |
247 | if (entry->addr + entry->size < minimum) | |
248 | return; | |
249 | ||
250 | region.start = entry->addr; | |
251 | region.size = entry->size; | |
252 | ||
253 | /* Potentially raise address to minimum location. */ | |
254 | if (region.start < minimum) | |
255 | region.start = minimum; | |
256 | ||
257 | /* Potentially raise address to meet alignment requirements. */ | |
258 | region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN); | |
259 | ||
260 | /* Did we raise the address above the bounds of this e820 region? */ | |
261 | if (region.start > entry->addr + entry->size) | |
262 | return; | |
263 | ||
264 | /* Reduce size by any delta from the original address. */ | |
265 | region.size -= region.start - entry->addr; | |
266 | ||
267 | /* Reduce maximum size to fit end of image within maximum limit. */ | |
268 | if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET) | |
269 | region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start; | |
270 | ||
271 | /* Walk each aligned slot and check for avoided areas. */ | |
272 | for (img.start = region.start, img.size = image_size ; | |
273 | mem_contains(®ion, &img) ; | |
274 | img.start += CONFIG_PHYSICAL_ALIGN) { | |
275 | if (mem_avoid_overlap(&img)) | |
276 | continue; | |
277 | slots_append(img.start); | |
278 | } | |
279 | } | |
280 | ||
281 | static unsigned long find_random_addr(unsigned long minimum, | |
282 | unsigned long size) | |
283 | { | |
284 | int i; | |
285 | unsigned long addr; | |
286 | ||
287 | /* Make sure minimum is aligned. */ | |
288 | minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN); | |
289 | ||
290 | /* Verify potential e820 positions, appending to slots list. */ | |
291 | for (i = 0; i < real_mode->e820_entries; i++) { | |
292 | process_e820_entry(&real_mode->e820_map[i], minimum, size); | |
293 | } | |
294 | ||
295 | return slots_fetch_random(); | |
296 | } | |
297 | ||
78cac48c BP |
298 | unsigned char *choose_kernel_location(struct boot_params *boot_params, |
299 | unsigned char *input, | |
8ab3820f KC |
300 | unsigned long input_size, |
301 | unsigned char *output, | |
302 | unsigned long output_size) | |
303 | { | |
304 | unsigned long choice = (unsigned long)output; | |
82fa9637 | 305 | unsigned long random; |
8ab3820f | 306 | |
24f2e027 KC |
307 | #ifdef CONFIG_HIBERNATION |
308 | if (!cmdline_find_option_bool("kaslr")) { | |
309 | debug_putstr("KASLR disabled by default...\n"); | |
310 | goto out; | |
311 | } | |
312 | #else | |
8ab3820f | 313 | if (cmdline_find_option_bool("nokaslr")) { |
24f2e027 | 314 | debug_putstr("KASLR disabled by cmdline...\n"); |
8ab3820f KC |
315 | goto out; |
316 | } | |
24f2e027 | 317 | #endif |
8ab3820f | 318 | |
78cac48c BP |
319 | boot_params->hdr.loadflags |= KASLR_FLAG; |
320 | ||
82fa9637 KC |
321 | /* Record the various known unsafe memory ranges. */ |
322 | mem_avoid_init((unsigned long)input, input_size, | |
323 | (unsigned long)output, output_size); | |
324 | ||
325 | /* Walk e820 and find a random address. */ | |
326 | random = find_random_addr(choice, output_size); | |
327 | if (!random) { | |
328 | debug_putstr("KASLR could not find suitable E820 region...\n"); | |
329 | goto out; | |
330 | } | |
331 | ||
332 | /* Always enforce the minimum. */ | |
333 | if (random < choice) | |
334 | goto out; | |
8ab3820f | 335 | |
82fa9637 | 336 | choice = random; |
8ab3820f KC |
337 | out: |
338 | return (unsigned char *)choice; | |
339 | } |