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

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Message-ID: <497d96a1-0532-ca18-8eaa-79fbcfd0b87d@arm.com>
Date:   Mon, 30 Mar 2020 17:13:44 +0530
From:   Amit Kachhap <amit.kachhap@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Will Deacon <will@...nel.org>,
        Vincenzo Frascino <Vincenzo.Frascino@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] arm64: Kconfig: ptrauth: Add binutils version check
 to fix mismatch



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@...el.com>
>> Suggested-by: Vincenzo Frascino <Vincenzo.Frascino@....com>
>> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
>> ---
>>   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
>