linux-kernel - Re: [PATCH v2 1/4] x86: Use the default ABI for the 32-bit vDSO

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Message-ID: <e33a0c21-5d74-4584-ac35-8cd45a905310@email.android.com>
Date:	Fri, 28 Feb 2014 07:06:29 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Stefani Seibold <stefani@...bold.net>,
	Andy Lutomirski <luto@...capital.net>
CC:	X86 ML <x86@...nel.org>, Greg KH <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	John Stultz <john.stultz@...aro.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	andriy.shevchenko@...ux.intel.com, Martin.Runge@...de-schwarz.com,
	Andreas.Brief@...de-schwarz.com
Subject: Re: [PATCH v2 1/4] x86: Use the default ABI for the 32-bit vDSO

How many internal function calls are there? It seems we should try to avoid those as much as possible by suitable inlining.

On February 27, 2014 11:28:25 PM PST, Stefani Seibold <stefani@...bold.net> wrote:
>Am Donnerstag, den 27.02.2014, 16:18 -0800 schrieb Andy Lutomirski:
>> There's no reason for the vDSO to use a special function call ABI. 
>Use
>> the platform defaults.
>> 
>
>The only reason was performance. What is good for the kernel should be
>also good for the VDSO. Now all functions inside the VDSO will pass the
>arguments by stack.
>
>> Signed-off-by: Andy Lutomirski <luto@...capital.net>
>> ---
>>  arch/x86/vdso/Makefile | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile
>> index 92daaa6..80584f5 100644
>> --- a/arch/x86/vdso/Makefile
>> +++ b/arch/x86/vdso/Makefile
>> @@ -149,7 +149,7 @@ KBUILD_CFLAGS_32 := $(filter-out
>-m64,$(KBUILD_CFLAGS))
>>  KBUILD_CFLAGS_32 := $(filter-out
>-mcmodel=kernel,$(KBUILD_CFLAGS_32))
>>  KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
>>  KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
>> -KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=3
>-freg-struct-return -fpic
>> +KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
>>  $(vdso32-images:%=$(obj)/%.dbg): KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)
>>  
>>  $(vdso32-images:%=$(obj)/%.dbg): $(obj)/vdso32-%.so.dbg: FORCE \

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
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