Building an arm64 defconfig with clang's integrated assembler, this error
occurs:
<instantiation>:2:2: error: unrecognized instruction mnemonic
_ASM_EXTABLE 9999b, 9f
^
arch/arm64/mm/cache.S:50:1: note: while in macro instantiation
user_alt 9f, "dc cvau, x4", "dc civac, x4", 0
^
While GNU as seems fine with case-sensitive macro instantiations, clang
doesn't, so use the actual macro name (_asm_extable) as in the rest of
the file.
Also checked that the generated assembly matches the GCC output.
Fixes: 290622efc76e ("arm64: fix "dc cvau" cache operation on errata-affected core")
Link: https://github.com/ClangBuiltLinux/linux/issues/924
Signed-off-by: Ilie Halip <[email protected]>
---
arch/arm64/include/asm/alternative.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
index 324e7d5ab37e..5e5dc05d63a0 100644
--- a/arch/arm64/include/asm/alternative.h
+++ b/arch/arm64/include/asm/alternative.h
@@ -221,7 +221,7 @@ alternative_endif
.macro user_alt, label, oldinstr, newinstr, cond
9999: alternative_insn "\oldinstr", "\newinstr", \cond
- _ASM_EXTABLE 9999b, \label
+ _asm_extable 9999b, \label
.endm
/*
--
2.17.1
On Thu, Mar 19, 2020 at 2:45 PM Ilie Halip <[email protected]> wrote:
>
> Building an arm64 defconfig with clang's integrated assembler, this error
> occurs:
> <instantiation>:2:2: error: unrecognized instruction mnemonic
> _ASM_EXTABLE 9999b, 9f
> ^
> arch/arm64/mm/cache.S:50:1: note: while in macro instantiation
> user_alt 9f, "dc cvau, x4", "dc civac, x4", 0
> ^
>
> While GNU as seems fine with case-sensitive macro instantiations, clang
> doesn't, so use the actual macro name (_asm_extable) as in the rest of
> the file.
>
> Also checked that the generated assembly matches the GCC output.
>
> Fixes: 290622efc76e ("arm64: fix "dc cvau" cache operation on errata-affected core")
> Link: https://github.com/ClangBuiltLinux/linux/issues/924
> Signed-off-by: Ilie Halip <[email protected]>
> ---
> arch/arm64/include/asm/alternative.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
> index 324e7d5ab37e..5e5dc05d63a0 100644
> --- a/arch/arm64/include/asm/alternative.h
> +++ b/arch/arm64/include/asm/alternative.h
> @@ -221,7 +221,7 @@ alternative_endif
>
> .macro user_alt, label, oldinstr, newinstr, cond
> 9999: alternative_insn "\oldinstr", "\newinstr", \cond
> - _ASM_EXTABLE 9999b, \label
> + _asm_extable 9999b, \label
> .endm
Testing a -next defconfig build, if I apply this, apply fixes for
https://github.com/ClangBuiltLinux/linux/issues/913, then disable
CONFIG_KVM, I can assemble (with Clang's integrated assembler) and
boot an aarch64 kernel. I think that's a first for Clang. Wow.
For CONFIG_KVM, I see:
arch/arm64/kvm/hyp/entry.S:112:87: error: too many positional arguments
alternative_insn nop, .inst (0xd500401f | ((0) << 16 | (4) << 5) |
((!!1) << 8)), 4, 1
^
which also uses `alternative_insn`, but not `user_alt`, so another bug
for us to look into, filed:
https://github.com/ClangBuiltLinux/linux/issues/939
Looks like `_asm_extable` itself is a macro, defined in
arch/arm64/include/asm/assembler.h on line 125. It's probably easy to
fix this in clang, but from a consistency with the rest of the file
(arch/arm64/include/asm/alternative.h) this patch should be accepted.
Reviewed-by: Nick Desaulniers <[email protected]>
Tested-by: Nick Desaulniers <[email protected]>
Should be easy to fix in Clang, too. Filed:
https://bugs.llvm.org/show_bug.cgi?id=45257
Thanks for the patch!
--
Thanks,
~Nick Desaulniers
On Thu, Mar 19, 2020 at 04:43:56PM -0700, Nick Desaulniers wrote:
> On Thu, Mar 19, 2020 at 2:45 PM Ilie Halip <[email protected]> wrote:
> >
> > Building an arm64 defconfig with clang's integrated assembler, this error
> > occurs:
> > <instantiation>:2:2: error: unrecognized instruction mnemonic
> > _ASM_EXTABLE 9999b, 9f
> > ^
> > arch/arm64/mm/cache.S:50:1: note: while in macro instantiation
> > user_alt 9f, "dc cvau, x4", "dc civac, x4", 0
> > ^
> >
> > While GNU as seems fine with case-sensitive macro instantiations, clang
> > doesn't, so use the actual macro name (_asm_extable) as in the rest of
> > the file.
> >
> > Also checked that the generated assembly matches the GCC output.
> >
> > Fixes: 290622efc76e ("arm64: fix "dc cvau" cache operation on errata-affected core")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/924
> > Signed-off-by: Ilie Halip <[email protected]>
> > ---
> > arch/arm64/include/asm/alternative.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
> > index 324e7d5ab37e..5e5dc05d63a0 100644
> > --- a/arch/arm64/include/asm/alternative.h
> > +++ b/arch/arm64/include/asm/alternative.h
> > @@ -221,7 +221,7 @@ alternative_endif
> >
> > .macro user_alt, label, oldinstr, newinstr, cond
> > 9999: alternative_insn "\oldinstr", "\newinstr", \cond
> > - _ASM_EXTABLE 9999b, \label
> > + _asm_extable 9999b, \label
> > .endm
>
> Testing a -next defconfig build, if I apply this, apply fixes for
> https://github.com/ClangBuiltLinux/linux/issues/913, then disable
> CONFIG_KVM, I can assemble (with Clang's integrated assembler) and
> boot an aarch64 kernel. I think that's a first for Clang. Wow.
>
> For CONFIG_KVM, I see:
> arch/arm64/kvm/hyp/entry.S:112:87: error: too many positional arguments
> alternative_insn nop, .inst (0xd500401f | ((0) << 16 | (4) << 5) |
> ((!!1) << 8)), 4, 1
>
> ^
> which also uses `alternative_insn`, but not `user_alt`, so another bug
> for us to look into, filed:
> https://github.com/ClangBuiltLinux/linux/issues/939
>
> Looks like `_asm_extable` itself is a macro, defined in
> arch/arm64/include/asm/assembler.h on line 125. It's probably easy to
> fix this in clang, but from a consistency with the rest of the file
> (arch/arm64/include/asm/alternative.h) this patch should be accepted.
>
> Reviewed-by: Nick Desaulniers <[email protected]>
> Tested-by: Nick Desaulniers <[email protected]>
Thanks, I'll pick this up as a fix.
Will