| Message ID | 1564605498-17629-1-git-send-email-cai@lca.pw (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64/mm: fix variable 'tag' set but not used | expand |
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? Will
> 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.
> On Aug 1, 2019, at 8:07 AM, Qian Cai <cai@lca.pw> wrote: > > > >> 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. If you are talking about “addr”, #define __tag_set(addr, tag) (addr) It is actually used.
On Thu, Aug 01, 2019 at 08:07:12AM -0400, Qian Cai wrote: > > > > 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. No, I mean because you're making addr 'const void *'. /me finds a toolchain. Look: In file included from ./arch/arm64/include/asm/pgtable-hwdef.h:8, from ./arch/arm64/include/asm/processor.h:35, from ./include/linux/mutex.h:19, from ./include/linux/kernfs.h:12, from ./include/linux/sysfs.h:16, from ./include/linux/kobject.h:20, from ./include/linux/of.h:17, from ./include/linux/irqdomain.h:35, from ./include/linux/acpi.h:13, from ./include/acpi/apei.h:9, from ./include/acpi/ghes.h:5, from ./include/linux/arm_sdei.h:14, from arch/arm64/kernel/asm-offsets.c:10: ./include/linux/mm.h: In function ‘lowmem_page_address’: ./arch/arm64/include/asm/memory.h:309:14: warning: passing argument 1 of ‘__tag_set’ makes pointer from integer without a cast [-Wint-conversion] __tag_set(__addr, page_kasan_tag(page)); \ ^~~~~~ ./include/linux/mm.h:1302:9: note: in expansion of macro ‘page_to_virt’ return page_to_virt(page); ^~~~~~~~~~~~ ./arch/arm64/include/asm/memory.h:213:49: note: expected ‘const void *’ but argument is of type ‘long unsigned int’ static inline const void *__tag_set(const void *addr, u8 tag) ~~~~~~~~~~~~^~~~ ./arch/arm64/include/asm/memory.h:309:4: warning: initialization of ‘long unsigned int’ from ‘const void *’ makes integer from pointer without a cast [-Wint-conversion] __tag_set(__addr, page_kasan_tag(page)); \ ^~~~~~~~~ ./include/linux/mm.h:1302:9: note: in expansion of macro ‘page_to_virt’ return page_to_virt(page); ^~~~~~~~~~~~ If you're going to send patches removing compiler warnings, please have the courtesy to test them first. Will
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; +} + #define __tag_reset(addr) (addr) #define __tag_get(addr) 0 #endif
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(-)