1/*
  2 * This file contains kasan initialization code for ARM64.
  3 *
  4 * Copyright (c) 2015 Samsung Electronics Co., Ltd.
  5 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License version 2 as
  9 * published by the Free Software Foundation.
 10 *
 11 */
 12
 13#define pr_fmt(fmt) "kasan: " fmt
 14#include <linux/kasan.h>
 15#include <linux/kernel.h>
 16#include <linux/memblock.h>
 17#include <linux/start_kernel.h>
 18
 19#include <asm/mmu_context.h>
 20#include <asm/kernel-pgtable.h>
 21#include <asm/page.h>
 22#include <asm/pgalloc.h>
 23#include <asm/pgtable.h>
 24#include <asm/sections.h>
 25#include <asm/tlbflush.h>
 26
 27static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
 28
 29static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr,
 30					unsigned long end)
 31{
 32	pte_t *pte;
 33	unsigned long next;
 34
 35	if (pmd_none(*pmd))
 36		pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
 37
 38	pte = pte_offset_kimg(pmd, addr);
 39	do {
 40		next = addr + PAGE_SIZE;
 41		set_pte(pte, pfn_pte(virt_to_pfn(kasan_zero_page),
 42					PAGE_KERNEL));
 43	} while (pte++, addr = next, addr != end && pte_none(*pte));
 44}
 45
 46static void __init kasan_early_pmd_populate(pud_t *pud,
 47					unsigned long addr,
 48					unsigned long end)
 49{
 50	pmd_t *pmd;
 51	unsigned long next;
 52
 53	if (pud_none(*pud))
 54		pud_populate(&init_mm, pud, kasan_zero_pmd);
 55
 56	pmd = pmd_offset_kimg(pud, addr);
 57	do {
 58		next = pmd_addr_end(addr, end);
 59		kasan_early_pte_populate(pmd, addr, next);
 60	} while (pmd++, addr = next, addr != end && pmd_none(*pmd));
 61}
 62
 63static void __init kasan_early_pud_populate(pgd_t *pgd,
 64					unsigned long addr,
 65					unsigned long end)
 66{
 67	pud_t *pud;
 68	unsigned long next;
 69
 70	if (pgd_none(*pgd))
 71		pgd_populate(&init_mm, pgd, kasan_zero_pud);
 72
 73	pud = pud_offset_kimg(pgd, addr);
 74	do {
 75		next = pud_addr_end(addr, end);
 76		kasan_early_pmd_populate(pud, addr, next);
 77	} while (pud++, addr = next, addr != end && pud_none(*pud));
 78}
 79
 80static void __init kasan_map_early_shadow(void)
 81{
 82	unsigned long addr = KASAN_SHADOW_START;
 83	unsigned long end = KASAN_SHADOW_END;
 84	unsigned long next;
 85	pgd_t *pgd;
 86
 87	pgd = pgd_offset_k(addr);
 88	do {
 89		next = pgd_addr_end(addr, end);
 90		kasan_early_pud_populate(pgd, addr, next);
 91	} while (pgd++, addr = next, addr != end);
 92}
 93
 94asmlinkage void __init kasan_early_init(void)
 95{
 96	BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_END - (1UL << 61));
 97	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
 98	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
 99	kasan_map_early_shadow();
100}
101
102/*
103 * Copy the current shadow region into a new pgdir.
104 */
105void __init kasan_copy_shadow(pgd_t *pgdir)
106{
107	pgd_t *pgd, *pgd_new, *pgd_end;
108
109	pgd = pgd_offset_k(KASAN_SHADOW_START);
110	pgd_end = pgd_offset_k(KASAN_SHADOW_END);
111	pgd_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START);
112	do {
113		set_pgd(pgd_new, *pgd);
114	} while (pgd++, pgd_new++, pgd != pgd_end);
115}
116
117static void __init clear_pgds(unsigned long start,
118			unsigned long end)
119{
120	/*
121	 * Remove references to kasan page tables from
122	 * swapper_pg_dir. pgd_clear() can't be used
123	 * here because it's nop on 2,3-level pagetable setups
124	 */
125	for (; start < end; start += PGDIR_SIZE)
126		set_pgd(pgd_offset_k(start), __pgd(0));
127}
128
129void __init kasan_init(void)
130{
131	u64 kimg_shadow_start, kimg_shadow_end;
132	u64 mod_shadow_start, mod_shadow_end;
133	struct memblock_region *reg;
134	int i;
135
136	kimg_shadow_start = (u64)kasan_mem_to_shadow(_text);
137	kimg_shadow_end = (u64)kasan_mem_to_shadow(_end);
138
139	mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
140	mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
141
142	/*
143	 * We are going to perform proper setup of shadow memory.
144	 * At first we should unmap early shadow (clear_pgds() call bellow).
145	 * However, instrumented code couldn't execute without shadow memory.
146	 * tmp_pg_dir used to keep early shadow mapped until full shadow
147	 * setup will be finished.
148	 */
149	memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
150	dsb(ishst);
151	cpu_replace_ttbr1(tmp_pg_dir);
152
153	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
154
155	vmemmap_populate(kimg_shadow_start, kimg_shadow_end,
156			 pfn_to_nid(virt_to_pfn(_text)));
157
158	/*
159	 * vmemmap_populate() has populated the shadow region that covers the
160	 * kernel image with SWAPPER_BLOCK_SIZE mappings, so we have to round
161	 * the start and end addresses to SWAPPER_BLOCK_SIZE as well, to prevent
162	 * kasan_populate_zero_shadow() from replacing the page table entries
163	 * (PMD or PTE) at the edges of the shadow region for the kernel
164	 * image.
165	 */
166	kimg_shadow_start = round_down(kimg_shadow_start, SWAPPER_BLOCK_SIZE);
167	kimg_shadow_end = round_up(kimg_shadow_end, SWAPPER_BLOCK_SIZE);
168
169	kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
170				   (void *)mod_shadow_start);
171	kasan_populate_zero_shadow((void *)kimg_shadow_end,
172				   kasan_mem_to_shadow((void *)PAGE_OFFSET));
173
174	if (kimg_shadow_start > mod_shadow_end)
175		kasan_populate_zero_shadow((void *)mod_shadow_end,
176					   (void *)kimg_shadow_start);
177
178	for_each_memblock(memory, reg) {
179		void *start = (void *)__phys_to_virt(reg->base);
180		void *end = (void *)__phys_to_virt(reg->base + reg->size);
181
182		if (start >= end)
183			break;
184
185		/*
186		 * end + 1 here is intentional. We check several shadow bytes in
187		 * advance to slightly speed up fastpath. In some rare cases
188		 * we could cross boundary of mapped shadow, so we just map
189		 * some more here.
190		 */
191		vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
192				(unsigned long)kasan_mem_to_shadow(end) + 1,
193				pfn_to_nid(virt_to_pfn(start)));
194	}
195
196	/*
197	 * KAsan may reuse the contents of kasan_zero_pte directly, so we
198	 * should make sure that it maps the zero page read-only.
199	 */
200	for (i = 0; i < PTRS_PER_PTE; i++)
201		set_pte(&kasan_zero_pte[i],
202			pfn_pte(virt_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
203
204	memset(kasan_zero_page, 0, PAGE_SIZE);
205	cpu_replace_ttbr1(swapper_pg_dir);
206
207	/* At this point kasan is fully initialized. Enable error messages */
208	init_task.kasan_depth = 0;
209	pr_info("KernelAddressSanitizer initialized\n");
210}