On Wed, Oct 28, 2020 at 12:08 PM Dmitry Vyukov [off-list ref] wrote:

On Thu, Oct 22, 2020 at 3:19 PM Andrey Konovalov [off-list ref] wrote:

quoted

Using random_tag() currently results in a function call. Move its
definition to mm/kasan/kasan.h and turn it into a static inline function
for hardware tag-based mode to avoid uneeded function call.

Signed-off-by: Andrey Konovalov <redacted>
Link: https://linux-review.googlesource.com/id/Iac5b2faf9a912900e16cca6834d621f5d4abf427
---
 mm/kasan/hw_tags.c |  5 -----
 mm/kasan/kasan.h   | 37 ++++++++++++++++++++-----------------
 2 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index c3a0e83b5e7a..4c24bfcfeff9 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c

@@ -36,11 +36,6 @@ void kasan_unpoison_memory(const void *address, size_t size)
                          round_up(size, KASAN_GRANULE_SIZE), get_tag(address));
 }

-u8 random_tag(void)
-{
-       return get_random_tag();
-}
-
 bool check_invalid_free(void *addr)
 {
        u8 ptr_tag = get_tag(addr);

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 0ccbb3c4c519..94ba15c2f860 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h

@@ -188,6 +188,12 @@ static inline bool addr_has_metadata(const void *addr)

 #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */

+#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
+void print_tags(u8 addr_tag, const void *addr);
+#else
+static inline void print_tags(u8 addr_tag, const void *addr) { }
+#endif
+
 bool check_invalid_free(void *addr);

 void *find_first_bad_addr(void *addr, size_t size);

@@ -223,23 +229,6 @@ static inline void quarantine_reduce(void) { }
 static inline void quarantine_remove_cache(struct kmem_cache *cache) { }
 #endif

-#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
-
-void print_tags(u8 addr_tag, const void *addr);
-
-u8 random_tag(void);
-
-#else
-
-static inline void print_tags(u8 addr_tag, const void *addr) { }
-
-static inline u8 random_tag(void)
-{
-       return 0;
-}
-
-#endif
-
 #ifndef arch_kasan_set_tag
 static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 {

@@ -273,6 +262,20 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 #define get_mem_tag(addr)                      arch_get_mem_tag(addr)
 #define set_mem_tag_range(addr, size, tag)     arch_set_mem_tag_range((addr), (size), (tag))

+#ifdef CONFIG_KASAN_SW_TAGS
+u8 random_tag(void);
+#elif defined(CONFIG_KASAN_HW_TAGS)
+static inline u8 random_tag(void)
+{
+       return get_random_tag();

What's the difference between random_tag() and get_random_tag()? Do we
need both?

Not really. Will simplify this in the next version and give cleaner names.

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