[patch 21/60] kasan: separate metadata_fetch_row for each mode

[Andrew Morton <akpm@linux-foundation.org>]

From: Andrey Konovalov <andreyknvl@google.com>
Subject: kasan: separate metadata_fetch_row for each mode

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.

Link: https://lkml.kernel.org/r/5fb1ec0152bb1f521505017800387ec3e36ffe18.1606161801.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/kasan/kasan.h          |    8 +++++
 mm/kasan/report.c         |   56 +++++++++++++++++-------------------
 mm/kasan/report_generic.c |    5 +++
 mm/kasan/report_sw_tags.c |    5 +++
 4 files changed, 45 insertions(+), 29 deletions(-)

--- a/mm/kasan/kasan.h~kasan-separate-metadata_fetch_row-for-each-mode
+++ a/mm/kasan/kasan.h
@@ -58,6 +58,13 @@
 #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;
@@ -170,6 +177,7 @@ 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);
 
 #if defined(CONFIG_KASAN_GENERIC) && CONFIG_KASAN_STACK
 void print_address_stack_frame(const void *addr);
--- a/mm/kasan/report.c~kasan-separate-metadata_fetch_row-for-each-mode
+++ a/mm/kasan/report.c
@@ -33,12 +33,6 @@
 #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
@@ -238,55 +232,59 @@ static void print_address_description(vo
 	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;
 	}
 }
 
--- a/mm/kasan/report_generic.c~kasan-separate-metadata_fetch_row-for-each-mode
+++ a/mm/kasan/report_generic.c
@@ -123,6 +123,11 @@ const char *get_bug_type(struct kasan_ac
 	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);
+}
+
 #if CONFIG_KASAN_STACK
 static bool __must_check tokenize_frame_descr(const char **frame_descr,
 					      char *token, size_t max_tok_len,
--- a/mm/kasan/report_sw_tags.c~kasan-separate-metadata_fetch_row-for-each-mode
+++ a/mm/kasan/report_sw_tags.c
@@ -80,6 +80,11 @@ void *find_first_bad_addr(void *addr, si
 	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);
_