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-rw-r--r--mm/page_poison.c144
1 files changed, 144 insertions, 0 deletions
diff --git a/mm/page_poison.c b/mm/page_poison.c
new file mode 100644
index 000000000..ae0482cde
--- /dev/null
+++ b/mm/page_poison.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/highmem.h>
+#include <linux/page_ext.h>
+#include <linux/poison.h>
+#include <linux/ratelimit.h>
+#include <linux/kasan.h>
+
+static DEFINE_STATIC_KEY_FALSE_RO(want_page_poisoning);
+
+static int __init early_page_poison_param(char *buf)
+{
+ int ret;
+ bool tmp;
+
+ ret = strtobool(buf, &tmp);
+ if (ret)
+ return ret;
+
+ if (tmp)
+ static_branch_enable(&want_page_poisoning);
+ else
+ static_branch_disable(&want_page_poisoning);
+
+ return 0;
+}
+early_param("page_poison", early_page_poison_param);
+
+/**
+ * page_poisoning_enabled - check if page poisoning is enabled
+ *
+ * Return true if page poisoning is enabled, or false if not.
+ */
+bool page_poisoning_enabled(void)
+{
+ /*
+ * Assumes that debug_pagealloc_enabled is set before
+ * memblock_free_all.
+ * Page poisoning is debug page alloc for some arches. If
+ * either of those options are enabled, enable poisoning.
+ */
+ return (static_branch_unlikely(&want_page_poisoning) ||
+ (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
+ debug_pagealloc_enabled()));
+}
+EXPORT_SYMBOL_GPL(page_poisoning_enabled);
+
+static void poison_page(struct page *page)
+{
+ void *addr = kmap_atomic(page);
+
+ /* KASAN still think the page is in-use, so skip it. */
+ kasan_disable_current();
+ memset(addr, PAGE_POISON, PAGE_SIZE);
+ kasan_enable_current();
+ kunmap_atomic(addr);
+}
+
+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)
+{
+ static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
+ unsigned char *start;
+ unsigned char *end;
+
+ if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
+ return;
+
+ start = memchr_inv(mem, PAGE_POISON, bytes);
+ if (!start)
+ return;
+
+ for (end = mem + bytes - 1; end > start; end--) {
+ if (*end != PAGE_POISON)
+ break;
+ }
+
+ if (!__ratelimit(&ratelimit))
+ return;
+ else if (start == end && single_bit_flip(*start, PAGE_POISON))
+ pr_err("pagealloc: single bit error\n");
+ else
+ pr_err("pagealloc: memory corruption\n");
+
+ print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
+ end - start + 1, 1);
+ dump_stack();
+}
+
+static void unpoison_page(struct page *page)
+{
+ void *addr;
+
+ addr = kmap_atomic(page);
+ /*
+ * Page poisoning when enabled poisons each and every page
+ * that is freed to buddy. Thus no extra check is done to
+ * see if a page was poisoned.
+ */
+ check_poison_mem(addr, PAGE_SIZE);
+ kunmap_atomic(addr);
+}
+
+static void unpoison_pages(struct page *page, int n)
+{
+ int i;
+
+ for (i = 0; i < n; i++)
+ unpoison_page(page + i);
+}
+
+void kernel_poison_pages(struct page *page, int numpages, int enable)
+{
+ if (!page_poisoning_enabled())
+ return;
+
+ if (enable)
+ unpoison_pages(page, numpages);
+ else
+ poison_pages(page, numpages);
+}
+
+#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