* [PATCH v2] arm64/mm: fix variable 'tag' set but not used
@ 2019-08-01 14:47 Qian Cai
2019-08-01 16:00 ` Matthew Wilcox
2019-08-05 15:37 ` Andrey Konovalov
0 siblings, 2 replies; 4+ messages in thread
From: Qian Cai @ 2019-08-01 14:47 UTC (permalink / raw)
To: catalin.marinas, will
Cc: andreyknvl, aryabinin, glider, dvyukov, linux-arm-kernel,
kasan-dev, linux-mm, linux-kernel, Qian Cai
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>
---
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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] arm64/mm: fix variable 'tag' set but not used
2019-08-01 14:47 [PATCH v2] arm64/mm: fix variable 'tag' set but not used Qian Cai
@ 2019-08-01 16:00 ` Matthew Wilcox
2019-08-01 16:20 ` Qian Cai
2019-08-05 15:37 ` Andrey Konovalov
1 sibling, 1 reply; 4+ messages in thread
From: Matthew Wilcox @ 2019-08-01 16:00 UTC (permalink / raw)
To: Qian Cai
Cc: catalin.marinas, will, andreyknvl, aryabinin, glider, dvyukov,
linux-arm-kernel, kasan-dev, linux-mm, linux-kernel
On Thu, Aug 01, 2019 at 10:47:05AM -0400, Qian Cai wrote:
Given this:
> -#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); \
> })
Can't you simplify that macro to:
#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)); \
- ((void *)__addr_tag); \
+ __tag_set((void *)__addr, page_kasan_tag(page)); \
})
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] arm64/mm: fix variable 'tag' set but not used
2019-08-01 16:00 ` Matthew Wilcox
@ 2019-08-01 16:20 ` Qian Cai
0 siblings, 0 replies; 4+ messages in thread
From: Qian Cai @ 2019-08-01 16:20 UTC (permalink / raw)
To: Matthew Wilcox
Cc: catalin.marinas, will, andreyknvl, aryabinin, glider, dvyukov,
linux-arm-kernel, kasan-dev, linux-mm, linux-kernel
On Thu, 2019-08-01 at 09:00 -0700, Matthew Wilcox wrote:
> On Thu, Aug 01, 2019 at 10:47:05AM -0400, Qian Cai wrote:
>
> Given this:
>
> > -#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);
> > \
> > })
>
> Can't you simplify that macro to:
>
> #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)); \
> - ((void *)__addr_tag);
> \
> + __tag_set((void *)__addr, page_kasan_tag(page)); \
> })
It still need a cast or lowmem_page_address() will complain of a discarded
"const". It might be a bit harder to read when adding a cast as in,
((void *)__tag_set((void *)__addr, page_kasan_tag(page)));
But, that feel like more of a followup patch for me if ever needed.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] arm64/mm: fix variable 'tag' set but not used
2019-08-01 14:47 [PATCH v2] arm64/mm: fix variable 'tag' set but not used Qian Cai
2019-08-01 16:00 ` Matthew Wilcox
@ 2019-08-05 15:37 ` Andrey Konovalov
1 sibling, 0 replies; 4+ messages in thread
From: Andrey Konovalov @ 2019-08-05 15:37 UTC (permalink / raw)
To: Qian Cai
Cc: Catalin Marinas, Will Deacon, Andrey Ryabinin,
Alexander Potapenko, Dmitry Vyukov, Linux ARM, kasan-dev,
Linux Memory Management List, LKML
On Thu, Aug 1, 2019 at 4:47 PM Qian Cai <cai@lca.pw> 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@lca.pw>
> ---
>
> 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@google.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-08-01 14:47 [PATCH v2] arm64/mm: fix variable 'tag' set but not used Qian Cai
2019-08-01 16:00 ` Matthew Wilcox
2019-08-01 16:20 ` Qian Cai
2019-08-05 15:37 ` Andrey Konovalov
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