1 // SPDX-License-Identifier: GPL-2.0
2
3 /*
4 * Transitional page tables for kexec and hibernate
5 *
6 * This file derived from: arch/arm64/kernel/hibernate.c
7 *
8 * Copyright (c) 2021, Microsoft Corporation.
9 * Pasha Tatashin <pasha.tatashin@soleen.com>
10 *
11 */
12
13 /*
14 * Transitional tables are used during system transferring from one world to
15 * another: such as during hibernate restore, and kexec reboots. During these
16 * phases one cannot rely on page table not being overwritten. This is because
17 * hibernate and kexec can overwrite the current page tables during transition.
18 */
19
20 #include <asm/trans_pgd.h>
21 #include <asm/pgalloc.h>
22 #include <asm/pgtable.h>
23 #include <linux/suspend.h>
24 #include <linux/bug.h>
25 #include <linux/mm.h>
26 #include <linux/mmzone.h>
27 #include <linux/kfence.h>
28
29 static void *trans_alloc(struct trans_pgd_info *info)
30 {
31 return info->trans_alloc_page(info->trans_alloc_arg);
32 }
33
34 static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr)
35 {
36 pte_t pte = __ptep_get(src_ptep);
37
38 if (pte_valid(pte)) {
39 /*
40 * Resume will overwrite areas that may be marked
41 * read only (code, rodata). Clear the RDONLY bit from
42 * the temporary mappings we use during restore.
43 */
44 __set_pte(dst_ptep, pte_mkwrite_novma(pte));
45 } else if (!pte_none(pte)) {
46 /*
47 * debug_pagealloc will removed the PTE_VALID bit if
48 * the page isn't in use by the resume kernel. It may have
49 * been in use by the original kernel, in which case we need
50 * to put it back in our copy to do the restore.
51 *
52 * Other cases include kfence / vmalloc / memfd_secret which
53 * may call `set_direct_map_invalid_noflush()`.
54 *
55 * Before marking this entry valid, check the pfn should
56 * be mapped.
57 */
58 BUG_ON(!pfn_valid(pte_pfn(pte)));
59
60 __set_pte(dst_ptep, pte_mkpresent(pte_mkwrite_novma(pte)));
61 }
62 }
63
64 static int copy_pte(struct trans_pgd_info *info, pmd_t *dst_pmdp,
65 pmd_t *src_pmdp, unsigned long start, unsigned long end)
66 {
67 pte_t *src_ptep;
68 pte_t *dst_ptep;
69 unsigned long addr = start;
70
71 dst_ptep = trans_alloc(info);
72 if (!dst_ptep)
73 return -ENOMEM;
74 pmd_populate_kernel(NULL, dst_pmdp, dst_ptep);
75 dst_ptep = pte_offset_kernel(dst_pmdp, start);
76
77 src_ptep = pte_offset_kernel(src_pmdp, start);
78 do {
79 _copy_pte(dst_ptep, src_ptep, addr);
80 } while (dst_ptep++, src_ptep++, addr += PAGE_SIZE, addr != end);
81
82 return 0;
83 }
84
85 static int copy_pmd(struct trans_pgd_info *info, pud_t *dst_pudp,
86 pud_t *src_pudp, unsigned long start, unsigned long end)
87 {
88 pmd_t *src_pmdp;
89 pmd_t *dst_pmdp;
90 unsigned long next;
91 unsigned long addr = start;
92
93 if (pud_none(READ_ONCE(*dst_pudp))) {
94 dst_pmdp = trans_alloc(info);
95 if (!dst_pmdp)
96 return -ENOMEM;
97 pud_populate(NULL, dst_pudp, dst_pmdp);
98 }
99 dst_pmdp = pmd_offset(dst_pudp, start);
100
101 src_pmdp = pmd_offset(src_pudp, start);
102 do {
103 pmd_t pmd = READ_ONCE(*src_pmdp);
104
105 next = pmd_addr_end(addr, end);
106 if (pmd_none(pmd))
107 continue;
108 if (pmd_table(pmd)) {
109 if (copy_pte(info, dst_pmdp, src_pmdp, addr, next))
110 return -ENOMEM;
111 } else {
112 set_pmd(dst_pmdp,
113 __pmd(pmd_val(pmd) & ~PMD_SECT_RDONLY));
114 }
115 } while (dst_pmdp++, src_pmdp++, addr = next, addr != end);
116
117 return 0;
118 }
119
120 static int copy_pud(struct trans_pgd_info *info, p4d_t *dst_p4dp,
121 p4d_t *src_p4dp, unsigned long start,
122 unsigned long end)
123 {
124 pud_t *dst_pudp;
125 pud_t *src_pudp;
126 unsigned long next;
127 unsigned long addr = start;
128
129 if (p4d_none(READ_ONCE(*dst_p4dp))) {
130 dst_pudp = trans_alloc(info);
131 if (!dst_pudp)
132 return -ENOMEM;
133 p4d_populate(NULL, dst_p4dp, dst_pudp);
134 }
135 dst_pudp = pud_offset(dst_p4dp, start);
136
137 src_pudp = pud_offset(src_p4dp, start);
138 do {
139 pud_t pud = READ_ONCE(*src_pudp);
140
141 next = pud_addr_end(addr, end);
142 if (pud_none(pud))
143 continue;
144 if (pud_table(pud)) {
145 if (copy_pmd(info, dst_pudp, src_pudp, addr, next))
146 return -ENOMEM;
147 } else {
148 set_pud(dst_pudp,
149 __pud(pud_val(pud) & ~PUD_SECT_RDONLY));
150 }
151 } while (dst_pudp++, src_pudp++, addr = next, addr != end);
152
153 return 0;
154 }
155
156 static int copy_p4d(struct trans_pgd_info *info, pgd_t *dst_pgdp,
157 pgd_t *src_pgdp, unsigned long start,
158 unsigned long end)
159 {
160 p4d_t *dst_p4dp;
161 p4d_t *src_p4dp;
162 unsigned long next;
163 unsigned long addr = start;
164
165 dst_p4dp = p4d_offset(dst_pgdp, start);
166 src_p4dp = p4d_offset(src_pgdp, start);
167 do {
168 next = p4d_addr_end(addr, end);
169 if (p4d_none(READ_ONCE(*src_p4dp)))
170 continue;
171 if (copy_pud(info, dst_p4dp, src_p4dp, addr, next))
172 return -ENOMEM;
173 } while (dst_p4dp++, src_p4dp++, addr = next, addr != end);
174
175 return 0;
176 }
177
178 static int copy_page_tables(struct trans_pgd_info *info, pgd_t *dst_pgdp,
179 unsigned long start, unsigned long end)
180 {
181 unsigned long next;
182 unsigned long addr = start;
183 pgd_t *src_pgdp = pgd_offset_k(start);
184
185 dst_pgdp = pgd_offset_pgd(dst_pgdp, start);
186 do {
187 next = pgd_addr_end(addr, end);
188 if (pgd_none(READ_ONCE(*src_pgdp)))
189 continue;
190 if (copy_p4d(info, dst_pgdp, src_pgdp, addr, next))
191 return -ENOMEM;
192 } while (dst_pgdp++, src_pgdp++, addr = next, addr != end);
193
194 return 0;
195 }
196
197 /*
198 * Create trans_pgd and copy linear map.
199 * info: contains allocator and its argument
200 * dst_pgdp: new page table that is created, and to which map is copied.
201 * start: Start of the interval (inclusive).
202 * end: End of the interval (exclusive).
203 *
204 * Returns 0 on success, and -ENOMEM on failure.
205 */
206 int trans_pgd_create_copy(struct trans_pgd_info *info, pgd_t **dst_pgdp,
207 unsigned long start, unsigned long end)
208 {
209 int rc;
210 pgd_t *trans_pgd = trans_alloc(info);
211
212 if (!trans_pgd) {
213 pr_err("Failed to allocate memory for temporary page tables.\n");
214 return -ENOMEM;
215 }
216
217 rc = copy_page_tables(info, trans_pgd, start, end);
218 if (!rc)
219 *dst_pgdp = trans_pgd;
220
221 return rc;
222 }
223
224 /*
225 * The page we want to idmap may be outside the range covered by VA_BITS that
226 * can be built using the kernel's p?d_populate() helpers. As a one off, for a
227 * single page, we build these page tables bottom up and just assume that will
228 * need the maximum T0SZ.
229 *
230 * Returns 0 on success, and -ENOMEM on failure.
231 * On success trans_ttbr0 contains page table with idmapped page, t0sz is set to
232 * maximum T0SZ for this page.
233 */
234 int trans_pgd_idmap_page(struct trans_pgd_info *info, phys_addr_t *trans_ttbr0,
235 unsigned long *t0sz, void *page)
236 {
237 phys_addr_t dst_addr = virt_to_phys(page);
238 unsigned long pfn = __phys_to_pfn(dst_addr);
239 int max_msb = (dst_addr & GENMASK(52, 48)) ? 51 : 47;
240 int bits_mapped = PAGE_SHIFT - 4;
241 unsigned long level_mask, prev_level_entry, *levels[4];
242 int this_level, index, level_lsb, level_msb;
243
244 dst_addr &= PAGE_MASK;
245 prev_level_entry = pte_val(pfn_pte(pfn, PAGE_KERNEL_ROX));
246
247 for (this_level = 3; this_level >= 0; this_level--) {
248 levels[this_level] = trans_alloc(info);
249 if (!levels[this_level])
250 return -ENOMEM;
251
252 level_lsb = ARM64_HW_PGTABLE_LEVEL_SHIFT(this_level);
253 level_msb = min(level_lsb + bits_mapped, max_msb);
254 level_mask = GENMASK_ULL(level_msb, level_lsb);
255
256 index = (dst_addr & level_mask) >> level_lsb;
257 *(levels[this_level] + index) = prev_level_entry;
258
259 pfn = virt_to_pfn(levels[this_level]);
260 prev_level_entry = pte_val(pfn_pte(pfn,
261 __pgprot(PMD_TYPE_TABLE)));
262
263 if (level_msb == max_msb)
264 break;
265 }
266
267 *trans_ttbr0 = phys_to_ttbr(__pfn_to_phys(pfn));
268 *t0sz = TCR_T0SZ(max_msb + 1);
269
270 return 0;
271 }
272
273 /*
274 * Create a copy of the vector table so we can call HVC_SET_VECTORS or
275 * HVC_SOFT_RESTART from contexts where the table may be overwritten.
276 */
277 int trans_pgd_copy_el2_vectors(struct trans_pgd_info *info,
278 phys_addr_t *el2_vectors)
279 {
280 void *hyp_stub = trans_alloc(info);
281
282 if (!hyp_stub)
283 return -ENOMEM;
284 *el2_vectors = virt_to_phys(hyp_stub);
285 memcpy(hyp_stub, &trans_pgd_stub_vectors, ARM64_VECTOR_TABLE_LEN);
286 caches_clean_inval_pou((unsigned long)hyp_stub,
287 (unsigned long)hyp_stub +
288 ARM64_VECTOR_TABLE_LEN);
289 dcache_clean_inval_poc((unsigned long)hyp_stub,
290 (unsigned long)hyp_stub +
291 ARM64_VECTOR_TABLE_LEN);
292
293 return 0;
294 }
295
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