Re: [PATCH 2/2] arm64: Kconfig: ptrauth: Add binutils version check to fix mismatch

[Amit Kachhap]

On 3/27/20 6:25 PM, Catalin Marinas wrote:
> On Thu, Mar 26, 2020 at 09:02:00PM +0530, Amit Daniel Kachhap wrote:
> > Recent addition of ARM64_PTR_AUTH exposed a mismatch issue with binutils.
> > 9.1+ versions of gcc inserts a section note .note.gnu.property but this
> > can be used properly by binutils version greater than 2.33.1. If older
> > binutils are used then the following warnings are generated,
> >
> > aarch64-linux-ld: warning: arch/arm64/kernel/vdso/vgettimeofday.o: unsupported GNU_PROPERTY_TYPE (5) type: 0xc0000000
> > aarch64-linux-objdump: warning: arch/arm64/lib/csum.o: unsupported GNU_PROPERTY_TYPE (5) type: 0xc0000000
> > aarch64-linux-nm: warning: .tmp_vmlinux1: unsupported GNU_PROPERTY_TYPE (5) type: 0xc0000000
> >
> > This patch enables ARM64_PTR_AUTH when gcc and binutils versions are
> > compatible with each other. Older gcc which do not insert such section
> > continue to work as before.
> >
> > This scenario may not occur with clang as a recent commit 3b446c7d27ddd06
> > ("arm64: Kconfig: verify binutils support for ARM64_PTR_AUTH") masks
> > binutils version lesser then 2.34.
> >
> > Reported-by: kbuild test robot <lkp@xxxxxxxxx>
> > Suggested-by: Vincenzo Frascino <Vincenzo.Frascino@xxxxxxx>
> > Signed-off-by: Amit Daniel Kachhap <amit.kachhap@xxxxxxx>
> > ---
> >   arch/arm64/Kconfig | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index e6712b6..73135da 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -1503,7 +1503,7 @@ config ARM64_PTR_AUTH
> >   	default y
> >   	depends on !KVM || ARM64_VHE
> >   	depends on (CC_HAS_SIGN_RETURN_ADDRESS || CC_HAS_BRANCH_PROT_PAC_RET) && AS_HAS_PAC
> > -	depends on CC_IS_GCC || (CC_IS_CLANG && AS_HAS_CFI_NEGATE_RA_STATE)
> > +	depends on (CC_IS_GCC && (GCC_VERSION < 90100 || LD_VERSION >= 233010000)) || (CC_IS_CLANG && AS_HAS_CFI_NEGATE_RA_STATE)
>
> We should add some of the comments in the commit log to the Kconfig
> entry. I would also split this in two (equivalent to CC_IS_ implies):
>
> 	depends on !CC_IS_GCC || GCC_VERSION < 90100 || LD_VERSION >= 233010000
> 	depends on !CC_IS_CLANG || AS_HAS_CFI_NEGATE_RA_STATE
>
> and add a comment above the gcc/ld version checking.
>
> (not entirely identical to the original if CC is neither of them but I
> don't think we have this problem)

Re-posted v2 as per the suggestions.

Thanks,
Amit
>