Re: [PATCH] selftests/size: rework to use main instead of _start

[Shuah Khan]

On 03/07/2018 08:11 AM, Shuah Khan wrote:
> On 03/07/2018 06:07 AM, Anders Roxell wrote:
>> In a -ffreestanding environment without glibc, we shouldn't be able to
>> call either getenv or printf. It seems that printf() happens to work
>> fine, but it ends up using the glibc getenv(), which doesn't work unless
>> we call the glibc _start() function first.
>> Using _start() was originally meant as an optimization to reduce the
>> memory consumption of the test program itself, in order to get a more
>> accurate representation of the available RAM at system boot time.
>> However, it causes more problems than it helps, especially when run from
>> a shell script that also consumes some memory.
>>
>> get_size[2838]: segfault at ffffffffffffffd0 ip 000000000040538b
>>    sp 00007ffc41980668 error 5 in get_size[400000+b0000]
>> audit: type=1701 audit(1521532923.838:4): auid=0 uid=0 gid=0 ses=2
>>    subj=kernel pid=2838 comm=\"get_size\"
>>    exe=\"/opt/kselftests/next/size/get_size\" sig=11 res=1
>> get_size[2840]: segfault at ffffffffffffffd0 ip 000000000040538b
>>    sp 00007ffdace9b378 error 5 in get_size[400000+b0000]
>> audit: type=1701 audit(1521532932.057:5): auid=0 uid=0 gid=0 ses=2
>>    subj=kernel pid=2840 comm=\"get_size\"
>>    exe=\"/opt/kselftests/next/size/get_size\" sig=11 res=1
>>
>> Rework to get_size test to use main (and printf) instead of _start. All
>> other seftest tests uses main and not _start.
>>
>> Fixes: 0081901af95f ("selftests: size call ksft_print_header() to print TAP header")
>> Signed-off-by: Anders Roxell <anders.roxell@xxxxxxxxxx>
> 
> Andres,
> 
> Thanks for finding and reporting the problem. This patch is in linux-kselftest next
> for 4.17-rc1. I would rather revert the patch than fix it a this time.
> 
> I knew there was a reason why Tim didn't use printf() in the first, I couldn't
> remember. I won't be sending
> 
> 0081901af95f ("selftests: size call ksft_print_header() to print TAP header")
> 
> for inclusion into 4.17-rc1
> 

Okay. Dropped the problem patch
0081901af95f ("selftests: size call ksft_print_header() to print TAP header")

from linux-kselftest next.

thanks again for finding the problem so quickly.
-- Shuah