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mm/page_poison.c
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// SPDX-License-Identifier: GPL-2.0 |
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#include <linux/kernel.h> |
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#include <linux/string.h> |
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#include <linux/mm.h> |
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#include <linux/highmem.h> |
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#include <linux/page_ext.h> |
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#include <linux/poison.h> |
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#include <linux/ratelimit.h> |
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#include <linux/kasan.h> |
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static bool want_page_poisoning __read_mostly; |
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static int __init early_page_poison_param(char *buf) |
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{ |
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if (!buf) return -EINVAL; |
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return strtobool(buf, &want_page_poisoning); |
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} early_param("page_poison", early_page_poison_param); |
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/** * page_poisoning_enabled - check if page poisoning is enabled * * Return true if page poisoning is enabled, or false if not. */ |
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bool page_poisoning_enabled(void) { |
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/* |
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* Assumes that debug_pagealloc_enabled is set before |
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* memblock_free_all. |
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* Page poisoning is debug page alloc for some arches. If * either of those options are enabled, enable poisoning. |
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*/ |
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return (want_page_poisoning || (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) && debug_pagealloc_enabled())); |
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} |
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EXPORT_SYMBOL_GPL(page_poisoning_enabled); |
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static void poison_page(struct page *page) { |
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void *addr = kmap_atomic(page); |
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/* KASAN still think the page is in-use, so skip it. */ kasan_disable_current(); |
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memset(addr, PAGE_POISON, PAGE_SIZE); |
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kasan_enable_current(); |
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kunmap_atomic(addr); |
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} static void poison_pages(struct page *page, int n) { int i; for (i = 0; i < n; i++) poison_page(page + i); } static bool single_bit_flip(unsigned char a, unsigned char b) { unsigned char error = a ^ b; return error && !(error & (error - 1)); } static void check_poison_mem(unsigned char *mem, size_t bytes) { |
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static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10); |
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unsigned char *start; unsigned char *end; |
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if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY)) return; |
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start = memchr_inv(mem, PAGE_POISON, bytes); if (!start) |
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return; for (end = mem + bytes - 1; end > start; end--) { if (*end != PAGE_POISON) break; } |
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if (!__ratelimit(&ratelimit)) |
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return; else if (start == end && single_bit_flip(*start, PAGE_POISON)) |
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pr_err("pagealloc: single bit error "); |
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else |
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pr_err("pagealloc: memory corruption "); |
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print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start, end - start + 1, 1); dump_stack(); } |
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static void unpoison_page(struct page *page) { |
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void *addr; |
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addr = kmap_atomic(page); |
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/* * Page poisoning when enabled poisons each and every page * that is freed to buddy. Thus no extra check is done to |
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* see if a page was poisoned. |
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*/ |
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check_poison_mem(addr, PAGE_SIZE); |
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kunmap_atomic(addr); |
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} static void unpoison_pages(struct page *page, int n) { int i; for (i = 0; i < n; i++) unpoison_page(page + i); } |
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void kernel_poison_pages(struct page *page, int numpages, int enable) |
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{ |
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if (!page_poisoning_enabled()) |
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return; |
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if (enable) unpoison_pages(page, numpages); else poison_pages(page, numpages); } |
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#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC void __kernel_map_pages(struct page *page, int numpages, int enable) { /* This function does nothing, all work is done via poison pages */ } #endif |