[PATCH v2 6/8] arm64: alternatives: have callbacks take a cap

[Mark Rutland]

On Thu, Sep 29, 2022 at 12:01:24PM +0100, Jon Hunter wrote:
> 
> On 29/09/2022 11:47, Mark Rutland wrote:
> > On Thu, Sep 29, 2022 at 10:53:56AM +0100, Jon Hunter wrote:
> > > 
> > > On 27/09/2022 10:31, Jon Hunter wrote:
> > > 
> > > ...
> > > 
> > > > > diff --git a/arch/arm64/include/asm/alternative-macros.h
> > > > > b/arch/arm64/include/asm/alternative-macros.h
> > > > > index 7e157ab6cd505..189c31be163ce 100644
> > > > > --- a/arch/arm64/include/asm/alternative-macros.h
> > > > > +++ b/arch/arm64/include/asm/alternative-macros.h
> > > > > @@ -2,10 +2,16 @@
> > > > >    #ifndef __ASM_ALTERNATIVE_MACROS_H
> > > > >    #define __ASM_ALTERNATIVE_MACROS_H
> > > > > +#include <linux/const.h>
> > > > > +
> > > > >    #include <asm/cpucaps.h>
> > > > >    #include <asm/insn-def.h>
> > > > > -#define ARM64_CB_PATCH ARM64_NCAPS
> > > > > +#define ARM64_CB_BIT    (UL(1) << 15)
> > > > > +
> > > > > +#if ARM64_NCAPS >= ARM64_CB_BIT
> > > > > +#error "cpucaps have overflown ARM64_CB_BIT"
> > > > > +#endif
> > > > 
> > > > 
> > > > Some of our builders are failing and bisect is pointing to this commit.
> > > > Looks like they don't like the above and I see the following errors ...
> > > > 
> > > >     CC      arch/arm64/kvm/hyp/vhe/debug-sr.o
> > > > /tmp/ccY3kbki.s: Assembler messages:
> > > > /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
> > > > /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
> > > > /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
> > > > /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
> > > > /tmp/ccY3kbki.s:1600: Error: junk at end of line, first unrecognized
> > > > character is `L'
> > > > /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
> > > > /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
> > > > /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
> > > > /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
> > > > /tmp/ccY3kbki.s:1723: Error: junk at end of line, first unrecognized
> > > > character is `L'
> > > > scripts/Makefile.build:249: recipe for target
> > > > 'arch/arm64/kvm/hyp/vhe/debug-sr.o' failed
> > > > 
> > > > Seems that it does not like the 'UL' macro for some reason. Any thoughts?
> > > 
> > > 
> > > FYI, this issue is seen with GCC6 but GCC7 and beyond appear to work fine.
> > 
> > Hmm... IIRC there was an issue with some older binutils here not liking the UL
> > suffix, but I thought we'd moved beyond those versions now; can you tell me
> > exactly which binutils version you're using?
> > 
> > I currently can't run the kernel.org crosstool GCC 5.5.0 release on my machine
> > since something's going wrong looking for an older version of libisl.so than my
> > system provides; I'll see if I can get that going and test locally.
> > 
> > I suspect we can bodge around this with something like the diff below.
> > 
> > Thanks,
> > Mark.
> > 
> > ---->8----
> > diff --git a/arch/arm64/include/asm/alternative-macros.h b/arch/arm64/include/asm/alternative-macros.h
> > index 966767debaa3..4dd23bdbfb9e 100644
> > --- a/arch/arm64/include/asm/alternative-macros.h
> > +++ b/arch/arm64/include/asm/alternative-macros.h
> > @@ -2,12 +2,14 @@
> >   #ifndef __ASM_ALTERNATIVE_MACROS_H
> >   #define __ASM_ALTERNATIVE_MACROS_H
> > +#include <linux/bits.h>
> >   #include <linux/const.h>
> >   #include <asm/cpucaps.h>
> >   #include <asm/insn-def.h>
> > -#define ARM64_CB_BIT	(UL(1) << 15)
> > +#define ARM64_CB_SHIFT	15
> > +#define ARM64_CB_BIT	BIT(ARM64_CB_SHIFT)
> >   #if ARM64_NCAPS >= ARM64_CB_BIT
> >   #error "cpucaps have overflown ARM64_CB_BIT"
> > @@ -80,7 +82,7 @@
> >   	__ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))
> >   #define ALTERNATIVE_CB(oldinstr, feature, cb) \
> > -	__ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_BIT | (feature), 1, cb)
> > +	__ALTERNATIVE_CFG_CB(oldinstr, (1 << ARM64_CB_SHIFT) | (feature), 1, cb)
> >   #else
> >   #include <asm/assembler.h>
> > @@ -150,7 +152,7 @@
> >   .macro alternative_cb cap, cb
> >   	.set .Lasm_alt_mode, 0
> >   	.pushsection .altinstructions, "a"
> > -	altinstruction_entry 661f, \cb, ARM64_CB_BIT | \cap, 662f-661f, 0
> > +	altinstruction_entry 661f, \cb, (1 << ARM64_CB_SHIFT) | \cap, 662f-661f, 0
> >   	.popsection
> >   661:
> >   .endm
> 
> 
> Yes that fixes it.
> 
> Tested-by: Jon Hunter <jonathanh at nvidia.com>

Great!

Could you please let me know which version of binutils, so that we can add
something regarding that in a comment and in the commit message?

The output of ${CROSS_COMPILE}as --version would suffice.

With that, I can clean this up and send as a proper patch.

Thanks,
Mark.