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22#include <linux/kernel.h>
23#include <linux/init.h>
24#include <linux/random.h>
25
26#include <asm/pgalloc.h>
27#include <asm/pgtable.h>
28#include <asm/setup.h>
29#include <asm/kaslr.h>
30
31#include "mm_internal.h"
32
33#define TB_SHIFT 40
34
35
36
37
38
39
40
41
42
43
44
45
46static const unsigned long vaddr_start = __PAGE_OFFSET_BASE;
47
48#if defined(CONFIG_X86_ESPFIX64)
49static const unsigned long vaddr_end = ESPFIX_BASE_ADDR;
50#elif defined(CONFIG_EFI)
51static const unsigned long vaddr_end = EFI_VA_END;
52#else
53static const unsigned long vaddr_end = __START_KERNEL_map;
54#endif
55
56
57unsigned long page_offset_base = __PAGE_OFFSET_BASE;
58EXPORT_SYMBOL(page_offset_base);
59unsigned long vmalloc_base = __VMALLOC_BASE;
60EXPORT_SYMBOL(vmalloc_base);
61unsigned long vmemmap_base = __VMEMMAP_BASE;
62EXPORT_SYMBOL(vmemmap_base);
63
64
65
66
67
68
69static __initdata struct kaslr_memory_region {
70 unsigned long *base;
71 unsigned long size_tb;
72} kaslr_regions[] = {
73 { &page_offset_base, 1 << (__PHYSICAL_MASK_SHIFT - TB_SHIFT) },
74 { &vmalloc_base, VMALLOC_SIZE_TB },
75 { &vmemmap_base, 1 },
76};
77
78
79static inline unsigned long get_padding(struct kaslr_memory_region *region)
80{
81 return (region->size_tb << TB_SHIFT);
82}
83
84
85
86
87
88static inline bool kaslr_memory_enabled(void)
89{
90 return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN);
91}
92
93
94void __init kernel_randomize_memory(void)
95{
96 size_t i;
97 unsigned long vaddr = vaddr_start;
98 unsigned long rand, memory_tb;
99 struct rnd_state rand_state;
100 unsigned long remain_entropy;
101
102
103
104
105
106 BUILD_BUG_ON(vaddr_start >= vaddr_end);
107 BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) &&
108 vaddr_end >= EFI_VA_END);
109 BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) ||
110 IS_ENABLED(CONFIG_EFI)) &&
111 vaddr_end >= __START_KERNEL_map);
112 BUILD_BUG_ON(vaddr_end > __START_KERNEL_map);
113
114 if (!kaslr_memory_enabled())
115 return;
116
117
118
119
120
121 BUG_ON(kaslr_regions[0].base != &page_offset_base);
122 memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) +
123 CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;
124
125
126 if (memory_tb < kaslr_regions[0].size_tb)
127 kaslr_regions[0].size_tb = memory_tb;
128
129
130 remain_entropy = vaddr_end - vaddr_start;
131 for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++)
132 remain_entropy -= get_padding(&kaslr_regions[i]);
133
134 prandom_seed_state(&rand_state, kaslr_get_random_long("Memory"));
135
136 for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) {
137 unsigned long entropy;
138
139
140
141
142
143 entropy = remain_entropy / (ARRAY_SIZE(kaslr_regions) - i);
144 prandom_bytes_state(&rand_state, &rand, sizeof(rand));
145 if (IS_ENABLED(CONFIG_X86_5LEVEL))
146 entropy = (rand % (entropy + 1)) & P4D_MASK;
147 else
148 entropy = (rand % (entropy + 1)) & PUD_MASK;
149 vaddr += entropy;
150 *kaslr_regions[i].base = vaddr;
151
152
153
154
155
156 vaddr += get_padding(&kaslr_regions[i]);
157 if (IS_ENABLED(CONFIG_X86_5LEVEL))
158 vaddr = round_up(vaddr + 1, P4D_SIZE);
159 else
160 vaddr = round_up(vaddr + 1, PUD_SIZE);
161 remain_entropy -= entropy;
162 }
163}
164
165static void __meminit init_trampoline_pud(void)
166{
167 unsigned long paddr, paddr_next;
168 pgd_t *pgd;
169 pud_t *pud_page, *pud_page_tramp;
170 int i;
171
172 pud_page_tramp = alloc_low_page();
173
174 paddr = 0;
175 pgd = pgd_offset_k((unsigned long)__va(paddr));
176 pud_page = (pud_t *) pgd_page_vaddr(*pgd);
177
178 for (i = pud_index(paddr); i < PTRS_PER_PUD; i++, paddr = paddr_next) {
179 pud_t *pud, *pud_tramp;
180 unsigned long vaddr = (unsigned long)__va(paddr);
181
182 pud_tramp = pud_page_tramp + pud_index(paddr);
183 pud = pud_page + pud_index(vaddr);
184 paddr_next = (paddr & PUD_MASK) + PUD_SIZE;
185
186 *pud_tramp = *pud;
187 }
188
189 set_pgd(&trampoline_pgd_entry,
190 __pgd(_KERNPG_TABLE | __pa(pud_page_tramp)));
191}
192
193static void __meminit init_trampoline_p4d(void)
194{
195 unsigned long paddr, paddr_next;
196 pgd_t *pgd;
197 p4d_t *p4d_page, *p4d_page_tramp;
198 int i;
199
200 p4d_page_tramp = alloc_low_page();
201
202 paddr = 0;
203 pgd = pgd_offset_k((unsigned long)__va(paddr));
204 p4d_page = (p4d_t *) pgd_page_vaddr(*pgd);
205
206 for (i = p4d_index(paddr); i < PTRS_PER_P4D; i++, paddr = paddr_next) {
207 p4d_t *p4d, *p4d_tramp;
208 unsigned long vaddr = (unsigned long)__va(paddr);
209
210 p4d_tramp = p4d_page_tramp + p4d_index(paddr);
211 p4d = p4d_page + p4d_index(vaddr);
212 paddr_next = (paddr & P4D_MASK) + P4D_SIZE;
213
214 *p4d_tramp = *p4d;
215 }
216
217 set_pgd(&trampoline_pgd_entry,
218 __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp)));
219}
220
221
222
223
224
225void __meminit init_trampoline(void)
226{
227
228 if (!kaslr_memory_enabled()) {
229 init_trampoline_default();
230 return;
231 }
232
233 if (IS_ENABLED(CONFIG_X86_5LEVEL))
234 init_trampoline_p4d();
235 else
236 init_trampoline_pud();
237}
238