On Thu, Aug 1, 2019 at 4:47 PM Qian Cai <cai@xxxxxx> 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 the same as
> arch_kasan_set_tag() in mm/kasan/kasan.h for consistency because there
> is a macro in arch/arm64/include/asm/kasan.h,
>
> #define arch_kasan_set_tag(addr, tag) __tag_set(addr, tag)
>
> However, when CONFIG_DEBUG_VIRTUAL=n and CONFIG_SPARSEMEM_VMEMMAP=y,
> page_to_virt() will call __tag_set() with incorrect type of a
> parameter, so fix that as well. Also, still let page_to_virt() return
> "void *" instead of "const void *", so will not need to add a similar
> cast in lowmem_page_address().
>
> Signed-off-by: Qian Cai <cai@xxxxxx>
> ---
>
> v2: Fix compilation warnings of CONFIG_DEBUG_VIRTUAL=n spotted by Will.
>
> arch/arm64/include/asm/memory.h | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> index b7ba75809751..fb04f10a78ab 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;
> +}
> +
> #define __tag_reset(addr) (addr)
> #define __tag_get(addr) 0
> #endif
> @@ -301,8 +305,8 @@ static inline void *phys_to_virt(phys_addr_t x)
> #define page_to_virt(page) ({ \
> unsigned long __addr = \
> ((__page_to_voff(page)) | PAGE_OFFSET); \
> - unsigned long __addr_tag = \
> - __tag_set(__addr, page_kasan_tag(page)); \
> + const void *__addr_tag = \
> + __tag_set((void *)__addr, page_kasan_tag(page)); \
> ((void *)__addr_tag); \
> })
>
> --
> 1.8.3.1
>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
