8db26a3d47
Commit 11c9c7edae ("mm/page_poison.c: replace bool variable with static
key") changed page_poisoning_enabled() to a static key check. However,
the function is not inlined, so each check still involves a function call
with overhead not eliminated when page poisoning is disabled.
Analogically to how debug_pagealloc is handled, this patch converts
page_poisoning_enabled() back to boolean check, and introduces
page_poisoning_enabled_static() for fast paths. Both functions are
inlined.
The function kernel_poison_pages() is also called unconditionally and does
the static key check inside. Remove it from there and put it to callers.
Also split it to two functions kernel_poison_pages() and
kernel_unpoison_pages() instead of the confusing bool parameter.
Also optimize the check that enables page poisoning instead of
debug_pagealloc for architectures without proper debug_pagealloc support.
Move the check to init_mem_debugging_and_hardening() to enable a single
static key instead of having two static branches in
page_poisoning_enabled_static().
Link: https://lkml.kernel.org/r/20201113104033.22907-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Laura Abbott <labbott@kernel.org>
Cc: Mateusz Nosek <mateusznosek0@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
106 lines
2.4 KiB
C
106 lines
2.4 KiB
C
// 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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bool _page_poisoning_enabled_early;
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EXPORT_SYMBOL(_page_poisoning_enabled_early);
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DEFINE_STATIC_KEY_FALSE(_page_poisoning_enabled);
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EXPORT_SYMBOL(_page_poisoning_enabled);
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static int __init early_page_poison_param(char *buf)
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{
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return kstrtobool(buf, &_page_poisoning_enabled_early);
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}
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early_param("page_poison", early_page_poison_param);
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static void poison_page(struct page *page)
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{
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void *addr = kmap_atomic(page);
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/* KASAN still think the page is in-use, so skip it. */
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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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}
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void __kernel_poison_pages(struct page *page, int n)
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{
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int i;
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for (i = 0; i < n; i++)
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poison_page(page + i);
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}
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static bool single_bit_flip(unsigned char a, unsigned char b)
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{
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unsigned char error = a ^ b;
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return error && !(error & (error - 1));
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}
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static void check_poison_mem(unsigned char *mem, size_t bytes)
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{
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static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
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unsigned char *start;
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unsigned char *end;
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if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
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return;
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start = memchr_inv(mem, PAGE_POISON, bytes);
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if (!start)
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return;
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for (end = mem + bytes - 1; end > start; end--) {
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if (*end != PAGE_POISON)
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break;
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}
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if (!__ratelimit(&ratelimit))
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return;
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else if (start == end && single_bit_flip(*start, PAGE_POISON))
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pr_err("pagealloc: single bit error\n");
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else
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pr_err("pagealloc: memory corruption\n");
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print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
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end - start + 1, 1);
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dump_stack();
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}
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static void unpoison_page(struct page *page)
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{
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void *addr;
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addr = kmap_atomic(page);
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/*
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* Page poisoning when enabled poisons each and every page
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* 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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}
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void __kernel_unpoison_pages(struct page *page, int n)
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{
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int i;
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for (i = 0; i < n; i++)
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unpoison_page(page + i);
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}
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#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
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void __kernel_map_pages(struct page *page, int numpages, int enable)
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{
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/* This function does nothing, all work is done via poison pages */
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}
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#endif
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