arm64/mm: fix variable 'tag' set but not used

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@lca.pw>
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index b7ba75809751e62fb10a024cff7c687721f6e652..fb04f10a78ab35c462e251d0bacce3a05da9be32 100644 (file)
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -210,7 +210,11 @@ extern u64                 vabits_user;
 #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);                                           \
 })