linux-kernel - Re: [Patch v2] x86/build: require only gcc use -maccumulate-outgoing-args

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 04 May 2017 23:38:57 -0700
From:   hpa@...or.com
To:     Ingo Molnar <mingo@...nel.org>,
        Nick Desaulniers <nick.desaulniers@...il.com>
CC:     jpoimboe@...hat.com, tglx@...utronix.de, mingo@...hat.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v2] x86/build: require only gcc use -maccumulate-outgoing-args

On May 4, 2017 11:23:33 PM PDT, Ingo Molnar <mingo@...nel.org> wrote:
>
>* Nick Desaulniers <nick.desaulniers@...il.com> wrote:
>
>> Other compilers, like clang, treat unknown compiler flags as errors.
>> 
>> Signed-off-by: Nick Desaulniers <nick.desaulniers@...il.com>
>> ---
>>  arch/x86/Makefile | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
>> index 4430dd489620..12757a252e6b 100644
>> --- a/arch/x86/Makefile
>> +++ b/arch/x86/Makefile
>> @@ -179,7 +179,7 @@ ifdef CONFIG_JUMP_LABEL
>>  endif
>>  
>>  ifeq ($(ACCUMULATE_OUTGOING_ARGS), 1)
>> -	KBUILD_CFLAGS += -maccumulate-outgoing-args
>> +	KBUILD_CFLAGS += $(if $(filter
>gcc,$(cc-name)),-maccumulate-outgoing-args)
>>  endif
>>  
>>  # Stackpointer is addressed different for 32 bit and 64 bit x86
>
>The justification Josh gave for this pattern should be put into a
>comment and into 
>the changelog as well.
>
>Thanks,
>
>	Ingo

However, I don't think Josh's explanation is correct.  I am pretty sure it is a performance issue, not a correctness issue, and besides, a version of gcc that old won't be able to compile the kernel for other reasons, as evidenced by the fact that noone has complained about this option being mandatory.
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.