On Thu, Nov 29, 2018 at 04:13:37PM +0000, Will Deacon wrote:
> On Thu, Nov 29, 2018 at 09:10:39AM -0700, Nathan Chancellor wrote:
> > 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.
>
> Aha, that explains it. Thanks for clearing that up.
>
> > 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"); \
> > ^
>
> Can you try throwing another set of brackets around it, please?
>
> ((unsigned long)(v))
>
> Will
Thanks, that fixes the warning as well.
Nathan
