[PATCH 18/35] kasan: separate metadata_fetch_row for each mode

[Andrey Konovalov <andreyknvl@google.com>]

This is a preparatory commit for the upcoming addition of a new hardware
tag-based (MTE-based) KASAN mode.

Rework print_memory_metadata() to make it agnostic with regard to the
way metadata is stored. Allow providing a separate metadata_fetch_row()
implementation for each KASAN mode. Hardware tag-based KASAN will provide
its own implementation that doesn't use shadow memory.

No functional changes for software modes.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/kasan.h          |  8 ++++++
 mm/kasan/report.c         | 56 +++++++++++++++++++--------------------
 mm/kasan/report_generic.c |  5 ++++
 mm/kasan/report_tags.c    |  5 ++++
 4 files changed, 45 insertions(+), 29 deletions(-)

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 38fa4c202e9a..1d3c7c6ce771 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -56,6 +56,13 @@
 #define KASAN_ABI_VERSION 1
 #endif
 
+/* Metadata layout customization. */
+#define META_BYTES_PER_BLOCK 1
+#define META_BLOCKS_PER_ROW 16
+#define META_BYTES_PER_ROW (META_BLOCKS_PER_ROW * META_BYTES_PER_BLOCK)
+#define META_MEM_BYTES_PER_ROW (META_BYTES_PER_ROW * KASAN_GRANULE_SIZE)
+#define META_ROWS_AROUND_ADDR 2
+
 struct kasan_access_info {
 	const void *access_addr;
 	const void *first_bad_addr;
@@ -167,6 +174,7 @@ bool check_invalid_free(void *addr);
 
 void *find_first_bad_addr(void *addr, size_t size);
 const char *get_bug_type(struct kasan_access_info *info);
+void metadata_fetch_row(char *buffer, void *row);
 
 #ifdef CONFIG_KASAN_STACK_ENABLE
 void print_address_stack_frame(const void *addr);
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 6306673e7062..c904edab33b8 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -36,12 +36,6 @@
 #include "kasan.h"
 #include "../slab.h"
 
-/* Metadata layout customization. */
-#define META_BYTES_PER_BLOCK 1
-#define META_BLOCKS_PER_ROW 16
-#define META_BYTES_PER_ROW (META_BLOCKS_PER_ROW * META_BYTES_PER_BLOCK)
-#define META_ROWS_AROUND_ADDR 2
-
 static unsigned long kasan_flags;
 
 #define KASAN_BIT_REPORTED	0
@@ -241,55 +235,59 @@ static void print_address_description(void *addr, u8 tag)
 	print_address_stack_frame(addr);
 }
 
-static bool row_is_guilty(const void *row, const void *guilty)
+static bool meta_row_is_guilty(const void *row, const void *addr)
 {
-	return (row <= guilty) && (guilty < row + META_BYTES_PER_ROW);
+	return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
 }
 
-static int shadow_pointer_offset(const void *row, const void *shadow)
+static int meta_pointer_offset(const void *row, const void *addr)
 {
-	/* The length of ">ff00ff00ff00ff00: " is
-	 *    3 + (BITS_PER_LONG/8)*2 chars.
+	/*
+	 * Memory state around the buggy address:
+	 *  ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
+	 *  ...
+	 *
+	 * The length of ">ff00ff00ff00ff00: " is
+	 *    3 + (BITS_PER_LONG / 8) * 2 chars.
+	 * The length of each granule metadata is 2 bytes
+	 *    plus 1 byte for space.
 	 */
-	return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
-		(shadow - row) / META_BYTES_PER_BLOCK + 1;
+	return 3 + (BITS_PER_LONG / 8) * 2 +
+		(addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
 }
 
 static void print_memory_metadata(const void *addr)
 {
 	int i;
-	const void *shadow = kasan_mem_to_shadow(addr);
-	const void *shadow_row;
+	void *row;
 
-	shadow_row = (void *)round_down((unsigned long)shadow,
-					META_BYTES_PER_ROW)
-		- META_ROWS_AROUND_ADDR * META_BYTES_PER_ROW;
+	row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
+			- META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
 
 	pr_err("Memory state around the buggy address:\n");
 
 	for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
-		const void *kaddr = kasan_shadow_to_mem(shadow_row);
-		char buffer[4 + (BITS_PER_LONG/8)*2];
-		char shadow_buf[META_BYTES_PER_ROW];
+		char buffer[4 + (BITS_PER_LONG / 8) * 2];
+		char metadata[META_BYTES_PER_ROW];
 
 		snprintf(buffer, sizeof(buffer),
-			(i == 0) ? ">%px: " : " %px: ", kaddr);
+				(i == 0) ? ">%px: " : " %px: ", row);
+
 		/*
 		 * We should not pass a shadow pointer to generic
 		 * function, because generic functions may try to
 		 * access kasan mapping for the passed address.
 		 */
-		memcpy(shadow_buf, shadow_row, META_BYTES_PER_ROW);
+		metadata_fetch_row(&metadata[0], row);
+
 		print_hex_dump(KERN_ERR, buffer,
 			DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
-			shadow_buf, META_BYTES_PER_ROW, 0);
+			metadata, META_BYTES_PER_ROW, 0);
 
-		if (row_is_guilty(shadow_row, shadow))
-			pr_err("%*c\n",
-				shadow_pointer_offset(shadow_row, shadow),
-				'^');
+		if (meta_row_is_guilty(row, addr))
+			pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
 
-		shadow_row += META_BYTES_PER_ROW;
+		row += META_MEM_BYTES_PER_ROW;
 	}
 }
 
diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
index 29d30fae9421..6524651b5d2e 100644
--- a/mm/kasan/report_generic.c
+++ b/mm/kasan/report_generic.c
@@ -127,6 +127,11 @@ const char *get_bug_type(struct kasan_access_info *info)
 	return get_wild_bug_type(info);
 }
 
+void metadata_fetch_row(char *buffer, void *row)
+{
+	memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
+}
+
 #ifdef CONFIG_KASAN_STACK_ENABLE
 static bool __must_check tokenize_frame_descr(const char **frame_descr,
 					      char *token, size_t max_tok_len,
diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c
index 6ddb55676a7c..4060d0503462 100644
--- a/mm/kasan/report_tags.c
+++ b/mm/kasan/report_tags.c
@@ -85,6 +85,11 @@ void *find_first_bad_addr(void *addr, size_t size)
 	return p;
 }
 
+void metadata_fetch_row(char *buffer, void *row)
+{
+	memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
+}
+
 void print_tags(u8 addr_tag, const void *addr)
 {
 	u8 *shadow = (u8 *)kasan_mem_to_shadow(addr);
-- 
2.28.0.220.ged08abb693-goog