Messages in this thread | | | Subject | Re: [PATCH] arm64/mm: fix variable 'tag' set but not used | From | Qian Cai <> | Date | Thu, 1 Aug 2019 08:07:12 -0400 |
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> On Aug 1, 2019, at 8:01 AM, Will Deacon <will@kernel.org> wrote: > > On Wed, Jul 31, 2019 at 04:38:18PM -0400, Qian Cai wrote: >> When CONFIG_KASAN_SW_TAGS=n, set_tag() is compiled away. GCC throws a >> warning, >> >> mm/kasan/common.c: In function '__kasan_kmalloc': >> mm/kasan/common.c:464:5: warning: variable 'tag' set but not used >> [-Wunused-but-set-variable] >> u8 tag = 0xff; >> ^~~ >> >> Fix it by making __tag_set() a static inline function. >> >> Signed-off-by: Qian Cai <cai@lca.pw> >> --- >> arch/arm64/include/asm/memory.h | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h >> index b7ba75809751..9645b1340afe 100644 >> --- a/arch/arm64/include/asm/memory.h >> +++ b/arch/arm64/include/asm/memory.h >> @@ -210,7 +210,11 @@ static inline unsigned long kaslr_offset(void) >> #define __tag_reset(addr) untagged_addr(addr) >> #define __tag_get(addr) (__u8)((u64)(addr) >> 56) >> #else >> -#define __tag_set(addr, tag) (addr) >> +static inline const void *__tag_set(const void *addr, u8 tag) >> +{ >> + return addr; >> +} > > Why doesn't this trigger a warning in page_to_virt(), which passes an > unsigned long for the address parameter?
#define page_to_virt(page) … __tag_set(__addr, page_kasan_tag(page)); …
static inline u8 page_kasan_tag(const struct page *page) { return 0xff; }
GCC will see that “page” is used.
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