xref: /linux/arch/arm64/mm/kasan_init.c (revision 79790b6818e96c58fe2bffee1b418c16e64e7b80)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * This file contains kasan initialization code for ARM64.
4  *
5  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
7  */
8 
9 #define pr_fmt(fmt) "kasan: " fmt
10 #include <linux/kasan.h>
11 #include <linux/kernel.h>
12 #include <linux/sched/task.h>
13 #include <linux/memblock.h>
14 #include <linux/start_kernel.h>
15 #include <linux/mm.h>
16 
17 #include <asm/mmu_context.h>
18 #include <asm/kernel-pgtable.h>
19 #include <asm/page.h>
20 #include <asm/pgalloc.h>
21 #include <asm/sections.h>
22 #include <asm/tlbflush.h>
23 
24 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
25 
26 static pgd_t tmp_pg_dir[PTRS_PER_PTE] __initdata __aligned(PAGE_SIZE);
27 
28 /*
29  * The p*d_populate functions call virt_to_phys implicitly so they can't be used
30  * directly on kernel symbols (bm_p*d). All the early functions are called too
31  * early to use lm_alias so __p*d_populate functions must be used to populate
32  * with the physical address from __pa_symbol.
33  */
34 
kasan_alloc_zeroed_page(int node)35 static phys_addr_t __init kasan_alloc_zeroed_page(int node)
36 {
37 	void *p = memblock_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
38 					      __pa(MAX_DMA_ADDRESS),
39 					      MEMBLOCK_ALLOC_NOLEAKTRACE, node);
40 	if (!p)
41 		panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%llx\n",
42 		      __func__, PAGE_SIZE, PAGE_SIZE, node,
43 		      __pa(MAX_DMA_ADDRESS));
44 
45 	return __pa(p);
46 }
47 
kasan_alloc_raw_page(int node)48 static phys_addr_t __init kasan_alloc_raw_page(int node)
49 {
50 	void *p = memblock_alloc_try_nid_raw(PAGE_SIZE, PAGE_SIZE,
51 						__pa(MAX_DMA_ADDRESS),
52 						MEMBLOCK_ALLOC_NOLEAKTRACE,
53 						node);
54 	if (!p)
55 		panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%llx\n",
56 		      __func__, PAGE_SIZE, PAGE_SIZE, node,
57 		      __pa(MAX_DMA_ADDRESS));
58 
59 	return __pa(p);
60 }
61 
kasan_pte_offset(pmd_t * pmdp,unsigned long addr,int node,bool early)62 static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
63 				      bool early)
64 {
65 	if (pmd_none(READ_ONCE(*pmdp))) {
66 		phys_addr_t pte_phys = early ?
67 				__pa_symbol(kasan_early_shadow_pte)
68 					: kasan_alloc_zeroed_page(node);
69 		__pmd_populate(pmdp, pte_phys, PMD_TYPE_TABLE);
70 	}
71 
72 	return early ? pte_offset_kimg(pmdp, addr)
73 		     : pte_offset_kernel(pmdp, addr);
74 }
75 
kasan_pmd_offset(pud_t * pudp,unsigned long addr,int node,bool early)76 static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node,
77 				      bool early)
78 {
79 	if (pud_none(READ_ONCE(*pudp))) {
80 		phys_addr_t pmd_phys = early ?
81 				__pa_symbol(kasan_early_shadow_pmd)
82 					: kasan_alloc_zeroed_page(node);
83 		__pud_populate(pudp, pmd_phys, PUD_TYPE_TABLE);
84 	}
85 
86 	return early ? pmd_offset_kimg(pudp, addr) : pmd_offset(pudp, addr);
87 }
88 
kasan_pud_offset(p4d_t * p4dp,unsigned long addr,int node,bool early)89 static pud_t *__init kasan_pud_offset(p4d_t *p4dp, unsigned long addr, int node,
90 				      bool early)
91 {
92 	if (p4d_none(READ_ONCE(*p4dp))) {
93 		phys_addr_t pud_phys = early ?
94 				__pa_symbol(kasan_early_shadow_pud)
95 					: kasan_alloc_zeroed_page(node);
96 		__p4d_populate(p4dp, pud_phys, P4D_TYPE_TABLE);
97 	}
98 
99 	return early ? pud_offset_kimg(p4dp, addr) : pud_offset(p4dp, addr);
100 }
101 
kasan_p4d_offset(pgd_t * pgdp,unsigned long addr,int node,bool early)102 static p4d_t *__init kasan_p4d_offset(pgd_t *pgdp, unsigned long addr, int node,
103 				      bool early)
104 {
105 	if (pgd_none(READ_ONCE(*pgdp))) {
106 		phys_addr_t p4d_phys = early ?
107 				__pa_symbol(kasan_early_shadow_p4d)
108 					: kasan_alloc_zeroed_page(node);
109 		__pgd_populate(pgdp, p4d_phys, PGD_TYPE_TABLE);
110 	}
111 
112 	return early ? p4d_offset_kimg(pgdp, addr) : p4d_offset(pgdp, addr);
113 }
114 
kasan_pte_populate(pmd_t * pmdp,unsigned long addr,unsigned long end,int node,bool early)115 static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
116 				      unsigned long end, int node, bool early)
117 {
118 	unsigned long next;
119 	pte_t *ptep = kasan_pte_offset(pmdp, addr, node, early);
120 
121 	do {
122 		phys_addr_t page_phys = early ?
123 				__pa_symbol(kasan_early_shadow_page)
124 					: kasan_alloc_raw_page(node);
125 		if (!early)
126 			memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE);
127 		next = addr + PAGE_SIZE;
128 		__set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
129 	} while (ptep++, addr = next, addr != end && pte_none(__ptep_get(ptep)));
130 }
131 
kasan_pmd_populate(pud_t * pudp,unsigned long addr,unsigned long end,int node,bool early)132 static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
133 				      unsigned long end, int node, bool early)
134 {
135 	unsigned long next;
136 	pmd_t *pmdp = kasan_pmd_offset(pudp, addr, node, early);
137 
138 	do {
139 		next = pmd_addr_end(addr, end);
140 		kasan_pte_populate(pmdp, addr, next, node, early);
141 	} while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)));
142 }
143 
kasan_pud_populate(p4d_t * p4dp,unsigned long addr,unsigned long end,int node,bool early)144 static void __init kasan_pud_populate(p4d_t *p4dp, unsigned long addr,
145 				      unsigned long end, int node, bool early)
146 {
147 	unsigned long next;
148 	pud_t *pudp = kasan_pud_offset(p4dp, addr, node, early);
149 
150 	do {
151 		next = pud_addr_end(addr, end);
152 		kasan_pmd_populate(pudp, addr, next, node, early);
153 	} while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)));
154 }
155 
kasan_p4d_populate(pgd_t * pgdp,unsigned long addr,unsigned long end,int node,bool early)156 static void __init kasan_p4d_populate(pgd_t *pgdp, unsigned long addr,
157 				      unsigned long end, int node, bool early)
158 {
159 	unsigned long next;
160 	p4d_t *p4dp = kasan_p4d_offset(pgdp, addr, node, early);
161 
162 	do {
163 		next = p4d_addr_end(addr, end);
164 		kasan_pud_populate(p4dp, addr, next, node, early);
165 	} while (p4dp++, addr = next, addr != end && p4d_none(READ_ONCE(*p4dp)));
166 }
167 
kasan_pgd_populate(unsigned long addr,unsigned long end,int node,bool early)168 static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
169 				      int node, bool early)
170 {
171 	unsigned long next;
172 	pgd_t *pgdp;
173 
174 	pgdp = pgd_offset_k(addr);
175 	do {
176 		next = pgd_addr_end(addr, end);
177 		kasan_p4d_populate(pgdp, addr, next, node, early);
178 	} while (pgdp++, addr = next, addr != end);
179 }
180 
181 #if defined(CONFIG_ARM64_64K_PAGES) || CONFIG_PGTABLE_LEVELS > 4
182 #define SHADOW_ALIGN	P4D_SIZE
183 #else
184 #define SHADOW_ALIGN	PUD_SIZE
185 #endif
186 
187 /*
188  * Return whether 'addr' is aligned to the size covered by a root level
189  * descriptor.
190  */
root_level_aligned(u64 addr)191 static bool __init root_level_aligned(u64 addr)
192 {
193 	int shift = (ARM64_HW_PGTABLE_LEVELS(vabits_actual) - 1) * (PAGE_SHIFT - 3);
194 
195 	return (addr % (PAGE_SIZE << shift)) == 0;
196 }
197 
198 /* The early shadow maps everything to a single page of zeroes */
kasan_early_init(void)199 asmlinkage void __init kasan_early_init(void)
200 {
201 	BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=
202 		KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
203 	BUILD_BUG_ON(!IS_ALIGNED(_KASAN_SHADOW_START(VA_BITS), SHADOW_ALIGN));
204 	BUILD_BUG_ON(!IS_ALIGNED(_KASAN_SHADOW_START(VA_BITS_MIN), SHADOW_ALIGN));
205 	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, SHADOW_ALIGN));
206 
207 	if (!root_level_aligned(KASAN_SHADOW_START)) {
208 		/*
209 		 * The start address is misaligned, and so the next level table
210 		 * will be shared with the linear region. This can happen with
211 		 * 4 or 5 level paging, so install a generic pte_t[] as the
212 		 * next level. This prevents the kasan_pgd_populate call below
213 		 * from inserting an entry that refers to the shared KASAN zero
214 		 * shadow pud_t[]/p4d_t[], which could end up getting corrupted
215 		 * when the linear region is mapped.
216 		 */
217 		static pte_t tbl[PTRS_PER_PTE] __page_aligned_bss;
218 		pgd_t *pgdp = pgd_offset_k(KASAN_SHADOW_START);
219 
220 		set_pgd(pgdp, __pgd(__pa_symbol(tbl) | PGD_TYPE_TABLE));
221 	}
222 
223 	kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE,
224 			   true);
225 }
226 
227 /* Set up full kasan mappings, ensuring that the mapped pages are zeroed */
kasan_map_populate(unsigned long start,unsigned long end,int node)228 static void __init kasan_map_populate(unsigned long start, unsigned long end,
229 				      int node)
230 {
231 	kasan_pgd_populate(start & PAGE_MASK, PAGE_ALIGN(end), node, false);
232 }
233 
234 /*
235  * Return the descriptor index of 'addr' in the root level table
236  */
root_level_idx(u64 addr)237 static int __init root_level_idx(u64 addr)
238 {
239 	/*
240 	 * On 64k pages, the TTBR1 range root tables are extended for 52-bit
241 	 * virtual addressing, and TTBR1 will simply point to the pgd_t entry
242 	 * that covers the start of the 48-bit addressable VA space if LVA is
243 	 * not implemented. This means we need to index the table as usual,
244 	 * instead of masking off bits based on vabits_actual.
245 	 */
246 	u64 vabits = IS_ENABLED(CONFIG_ARM64_64K_PAGES) ? VA_BITS
247 							: vabits_actual;
248 	int shift = (ARM64_HW_PGTABLE_LEVELS(vabits) - 1) * (PAGE_SHIFT - 3);
249 
250 	return (addr & ~_PAGE_OFFSET(vabits)) >> (shift + PAGE_SHIFT);
251 }
252 
253 /*
254  * Clone a next level table from swapper_pg_dir into tmp_pg_dir
255  */
clone_next_level(u64 addr,pgd_t * tmp_pg_dir,pud_t * pud)256 static void __init clone_next_level(u64 addr, pgd_t *tmp_pg_dir, pud_t *pud)
257 {
258 	int idx = root_level_idx(addr);
259 	pgd_t pgd = READ_ONCE(swapper_pg_dir[idx]);
260 	pud_t *pudp = (pud_t *)__phys_to_kimg(__pgd_to_phys(pgd));
261 
262 	memcpy(pud, pudp, PAGE_SIZE);
263 	tmp_pg_dir[idx] = __pgd(__phys_to_pgd_val(__pa_symbol(pud)) |
264 				PUD_TYPE_TABLE);
265 }
266 
267 /*
268  * Return the descriptor index of 'addr' in the next level table
269  */
next_level_idx(u64 addr)270 static int __init next_level_idx(u64 addr)
271 {
272 	int shift = (ARM64_HW_PGTABLE_LEVELS(vabits_actual) - 2) * (PAGE_SHIFT - 3);
273 
274 	return (addr >> (shift + PAGE_SHIFT)) % PTRS_PER_PTE;
275 }
276 
277 /*
278  * Dereference the table descriptor at 'pgd_idx' and clear the entries from
279  * 'start' to 'end' (exclusive) from the table.
280  */
clear_next_level(int pgd_idx,int start,int end)281 static void __init clear_next_level(int pgd_idx, int start, int end)
282 {
283 	pgd_t pgd = READ_ONCE(swapper_pg_dir[pgd_idx]);
284 	pud_t *pudp = (pud_t *)__phys_to_kimg(__pgd_to_phys(pgd));
285 
286 	memset(&pudp[start], 0, (end - start) * sizeof(pud_t));
287 }
288 
clear_shadow(u64 start,u64 end)289 static void __init clear_shadow(u64 start, u64 end)
290 {
291 	int l = root_level_idx(start), m = root_level_idx(end);
292 
293 	if (!root_level_aligned(start))
294 		clear_next_level(l++, next_level_idx(start), PTRS_PER_PTE);
295 	if (!root_level_aligned(end))
296 		clear_next_level(m, 0, next_level_idx(end));
297 	memset(&swapper_pg_dir[l], 0, (m - l) * sizeof(pgd_t));
298 }
299 
kasan_init_shadow(void)300 static void __init kasan_init_shadow(void)
301 {
302 	static pud_t pud[2][PTRS_PER_PUD] __initdata __aligned(PAGE_SIZE);
303 	u64 kimg_shadow_start, kimg_shadow_end;
304 	u64 mod_shadow_start;
305 	u64 vmalloc_shadow_end;
306 	phys_addr_t pa_start, pa_end;
307 	u64 i;
308 
309 	kimg_shadow_start = (u64)kasan_mem_to_shadow(KERNEL_START) & PAGE_MASK;
310 	kimg_shadow_end = PAGE_ALIGN((u64)kasan_mem_to_shadow(KERNEL_END));
311 
312 	mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
313 
314 	vmalloc_shadow_end = (u64)kasan_mem_to_shadow((void *)VMALLOC_END);
315 
316 	/*
317 	 * We are going to perform proper setup of shadow memory.
318 	 * At first we should unmap early shadow (clear_pgds() call below).
319 	 * However, instrumented code couldn't execute without shadow memory.
320 	 * tmp_pg_dir used to keep early shadow mapped until full shadow
321 	 * setup will be finished.
322 	 */
323 	memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
324 
325 	/*
326 	 * If the start or end address of the shadow region is not aligned to
327 	 * the root level size, we have to allocate a temporary next-level table
328 	 * in each case, clone the next level of descriptors, and install the
329 	 * table into tmp_pg_dir. Note that with 5 levels of paging, the next
330 	 * level will in fact be p4d_t, but that makes no difference in this
331 	 * case.
332 	 */
333 	if (!root_level_aligned(KASAN_SHADOW_START))
334 		clone_next_level(KASAN_SHADOW_START, tmp_pg_dir, pud[0]);
335 	if (!root_level_aligned(KASAN_SHADOW_END))
336 		clone_next_level(KASAN_SHADOW_END, tmp_pg_dir, pud[1]);
337 	dsb(ishst);
338 	cpu_replace_ttbr1(lm_alias(tmp_pg_dir));
339 
340 	clear_shadow(KASAN_SHADOW_START, KASAN_SHADOW_END);
341 
342 	kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
343 			   early_pfn_to_nid(virt_to_pfn(lm_alias(KERNEL_START))));
344 
345 	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END),
346 				   (void *)mod_shadow_start);
347 
348 	BUILD_BUG_ON(VMALLOC_START != MODULES_END);
349 	kasan_populate_early_shadow((void *)vmalloc_shadow_end,
350 				    (void *)KASAN_SHADOW_END);
351 
352 	for_each_mem_range(i, &pa_start, &pa_end) {
353 		void *start = (void *)__phys_to_virt(pa_start);
354 		void *end = (void *)__phys_to_virt(pa_end);
355 
356 		if (start >= end)
357 			break;
358 
359 		kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),
360 				   (unsigned long)kasan_mem_to_shadow(end),
361 				   early_pfn_to_nid(virt_to_pfn(start)));
362 	}
363 
364 	/*
365 	 * KAsan may reuse the contents of kasan_early_shadow_pte directly,
366 	 * so we should make sure that it maps the zero page read-only.
367 	 */
368 	for (i = 0; i < PTRS_PER_PTE; i++)
369 		__set_pte(&kasan_early_shadow_pte[i],
370 			pfn_pte(sym_to_pfn(kasan_early_shadow_page),
371 				PAGE_KERNEL_RO));
372 
373 	memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
374 	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
375 }
376 
kasan_init_depth(void)377 static void __init kasan_init_depth(void)
378 {
379 	init_task.kasan_depth = 0;
380 }
381 
382 #ifdef CONFIG_KASAN_VMALLOC
kasan_populate_early_vm_area_shadow(void * start,unsigned long size)383 void __init kasan_populate_early_vm_area_shadow(void *start, unsigned long size)
384 {
385 	unsigned long shadow_start, shadow_end;
386 
387 	if (!is_vmalloc_or_module_addr(start))
388 		return;
389 
390 	shadow_start = (unsigned long)kasan_mem_to_shadow(start);
391 	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
392 	shadow_end = (unsigned long)kasan_mem_to_shadow(start + size);
393 	shadow_end = ALIGN(shadow_end, PAGE_SIZE);
394 	kasan_map_populate(shadow_start, shadow_end, NUMA_NO_NODE);
395 }
396 #endif
397 
kasan_init(void)398 void __init kasan_init(void)
399 {
400 	kasan_init_shadow();
401 	kasan_init_depth();
402 #if defined(CONFIG_KASAN_GENERIC)
403 	/*
404 	 * Generic KASAN is now fully initialized.
405 	 * Software and Hardware Tag-Based modes still require
406 	 * kasan_init_sw_tags() and kasan_init_hw_tags() correspondingly.
407 	 */
408 	pr_info("KernelAddressSanitizer initialized (generic)\n");
409 #endif
410 }
411 
412 #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
413