On Thu, Nov 29, 2018 at 10:49:03AM +0000, Will Deacon wrote:
> On Thu, Nov 29, 2018 at 09:03:54AM +0000, Julien Thierry wrote:
> >
> >
> > On 29/11/18 04:19, Nick Desaulniers wrote:
> > > Fixes the warning produced from Clang:
> > > ./include/asm-generic/io.h:711:9: warning: value size does not match
> > > register size specified by the constraint and modifier
> > > [-Wasm-operand-widths]
> > > return readl(addr);
> > > ^
> > > ./arch/arm64/include/asm/io.h:149:58: note: expanded from macro 'readl'
> > > ^
> > > ./include/asm-generic/io.h:711:9: note: use constraint modifier "w"
> > > ./arch/arm64/include/asm/io.h:149:50: note: expanded from macro 'readl'
> > > ^
> > > ./arch/arm64/include/asm/io.h:118:25: note: expanded from macro '__iormb'
> > > asm volatile("eor %w0, %1, %1\n" \
> > > ^
> >
> > Why does the "eor %0, %1, %1" become "eor %w0, %1, %1" ?
> > The variable passed to the inline assembly for %0 is unsigned long, so
> > always 64-bits wide on arm64. Why is clang trying to use a 32-bit
> > register for it?
Sorry, this was my fault, I accidentally added a w during testing to see
what constraints were valid (given that my assembly knowledge is nearly
non-existence so forgive the non-sensical experimentation) and I used
that message rather than the original one. This is the unadulterated one.
In file included from arch/arm64/kernel/asm-offsets.c:24:
In file included from ./include/linux/dma-mapping.h:11:
In file included from ./include/linux/scatterlist.h:9:
In file included from ./arch/arm64/include/asm/io.h:209:
./include/asm-generic/io.h:695:9: warning: value size does not match register
size specified by the constraint and modifier [-Wasm-operand-widths]
return readb(addr);
^
./arch/arm64/include/asm/io.h:147:58: note: expanded from macro 'readb'
#define readb(c) ({ u8 __v = readb_relaxed(c); __iormb(__v);
__v; })
^
./include/asm-generic/io.h:695:9: note: use constraint modifier "w"
./arch/arm64/include/asm/io.h:147:50: note: expanded from macro 'readb'
#define readb(c) ({ u8 __v = readb_relaxed(c); __iormb(__v);
__v; })
^
./arch/arm64/include/asm/io.h:118:24: note: expanded from macro '__iormb'
asm volatile("eor %0, %1, %1\n" \
^
>
> Yeah, the message above looks bogus to me. I can see %1 being 32-bit for
> read[bwl], so maybe clang is just getting the diagnostic wrong. If so,
> I wonder if the following fixes the problem:
>
This doesn't appear to work, I get this error:
In file included from arch/arm64/kernel/asm-offsets.c:24:
In file included from ./include/linux/dma-mapping.h:11:
In file included from ./include/linux/scatterlist.h:9:
In file included from ./arch/arm64/include/asm/io.h:209:
./include/asm-generic/io.h:695:9: error: expected expression
return readb(addr);
^
./arch/arm64/include/asm/io.h:147:50: note: expanded from macro 'readb'
#define readb(c) ({ u8 __v = readb_relaxed(c); __iormb(__v);
__v; })
^
./arch/arm64/include/asm/io.h:120:28: note: expanded from macro '__iormb'
: "=r" (tmp) : "r" (unsigned long)(v) : "memory"); \
^
>
> diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
> index d42d00d8d5b6..13befec8b64e 100644
> --- a/arch/arm64/include/asm/io.h
> +++ b/arch/arm64/include/asm/io.h
> @@ -117,7 +117,7 @@ static inline u64 __raw_readq(const volatile void __iomem
> *addr)
> */ \
> asm volatile("eor %0, %1, %1\n" \
> "cbnz %0, ." \
> - : "=r" (tmp) : "r" (v) : "memory"); \
> + : "=r" (tmp) : "r" (unsigned long)(v) : "memory"); \
> })
>
> #define __iowmb() wmb()
>
>
> Will
