linux-kernel - Re: [PATCH] uselib: default depending if libc5 was used

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Message-ID: <CAAqcGHmPDcP_CK0XTif=9YN3w51icN=8xpuXiC_CKDaBXdkrrg@mail.gmail.com>
Date:	Fri, 27 Nov 2015 12:48:29 +0200
From:	Riku Voipio <riku.voipio@...aro.org>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] uselib: default depending if libc5 was used

On 27 November 2015 at 11:33, Josh Triplett <josh@...htriplett.org> wrote:
> On Fri, Nov 27, 2015 at 11:11:26AM +0200, Riku Voipio wrote:
>> uselib hasn't been used since libc5; glibc does not use it.
>> Deprecate uselib a bit more, by making the default y only
>> if libc5 was widely used on the plaform.
>>
>> This makes arm64 kernel built with defconfig slighly smaller
>>
>> bloat-o-meter:
>> add/remove: 0/3 grow/shrink: 0/2 up/down: 0/-1390 (-1390)
>> function                                     old     new   delta
>> kernel_config_data                         18164   18162      -2
>> uselib_flags                                  20       -     -20
>> padzero                                      216     192     -24
>> sys_uselib                                   380       -    -380
>> load_elf_library                             964       -    -964
>>
>> Signed-off-by: Riku Voipio <riku.voipio@...aro.org>
>> Cc: Josh Triplett <josh@...htriplett.org>
>
> Seems sensible.  Can you also make it only "default y" on 32-bit x86,
> not 64-bit x86, since the latter never had libc5?

but running 32bit libc5 apps is possible with X86_64 kernel, so the
check would become:

|| X86_32 || (X86_64 && IA32_EMULATION)

> With that change:
> Reviewed-by: Josh Triplett <josh@...htriplett.org>
>
>>  init/Kconfig | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/init/Kconfig b/init/Kconfig
>> index c24b6f7..bef326d 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -285,7 +285,7 @@ config FHANDLE
>>
>>  config USELIB
>>       bool "uselib syscall"
>> -     default y
>> +     def_bool ALPHA || M68K || SPARC || X86
>>       help
>>         This option enables the uselib syscall, a system call used in the
>>         dynamic linker from libc5 and earlier.  glibc does not use this
>> --
>> 2.6.2
>>
--
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