Re: [PATCH v4] Fix Linux fcntl OFD locks for non-LFS architectures (BZ#20251)

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

On 05/07/2018 16:56, Carlos O'Donell wrote:
> On 07/02/2018 08:44 AM, Adhemerval Zanella wrote:
>>
>>
>> On 30/06/2018 09:26, Szabolcs Nagy wrote:
>>> * Adhemerval Zanella <adhemerval.zanella@linaro.org> [2018-06-20 18:43:13 -0300]:
>>>> This patch fixes the OFD ("file private") locks for architectures that
>>>> support non-LFS flock definition (__USE_FILE_OFFSET64 not defined). The
>>>> issue in this case is both F_OFD_{GETLK,SETLK,SETLKW} and
>>>> F_{SET,GET}L{W}K64 expects a flock64 argument and when using old
>>>> F_OFD_* flags with a non LFS flock argument the kernel might interpret
>>>> the underlying data wrongly.  Kernel idea originally was to avoid using
>>>> such flags in non-LFS syscall, but since GLIBC uses fcntl with LFS
>>>> semantic as default it is possible to provide the functionality and
>>>> avoid the bogus struct kernel passing by adjusting the struct manually
>>>> for the required flags.
>>>>
>>>> The idea follows other LFS interfaces that provide two symbols:
>>>>
>>>>   1. A new LFS fcntl64 is added on default ABI with the usual macros to
>>>>      select it for FILE_OFFSET_BITS=64.
>>>>
>>>>   2. The Linux non-LFS fcntl use a stack allocated struct flock64 for
>>>>      F_OFD_{GETLK,SETLK,SETLKW} copy the results on the user provided
>>>>      struct.
>>>>
>>>>   3. Keep a compat symbol with old broken semantic for architectures
>>>>      that do not define __OFF_T_MATCHES_OFF64_T.
>>>>
>>>> So for architectures which defines __USE_FILE_OFFSET64, fcntl64 will
>>>> aliased to fcntl and no adjustment would be required.  So to actually
>>>> use F_OFD_* with LFS support the source must be built with LFS support
>>>> (_FILE_OFFSET_BITS=64).
>>>>
>>>> Also F_OFD_SETLKW command is handled a cancellation point, as for
>>>> F_SETLKW{64}.
>>>>
>>>> Checked on x86_64-linux-gnu and i686-linux-gnu.
>>>>
>>>
>>> build-many-glibcs fails for me on i686
>>> in logs/glibcs/i686-gnu/010-glibcs-i686-gnu-check-log.txt i see
>>>
>>> FAIL: elf/check-abi-libc
>>> FAIL: elf/check-execstack
>>> FAIL: hurd/check-installed-headers-c
>>> FAIL: hurd/check-installed-headers-cxx
>>> FAIL: mach/check-installed-headers-c
>>> FAIL: mach/check-installed-headers-cxx
>>>
>>> the libc abi failure is
>>>
>>> --- ../sysdeps/mach/hurd/i386/libc.abilist      2018-06-29 18:53:06.105524353 +0100
>>> +++ /B/build/glibcs/i686-gnu/glibc/libc.symlist        2018-06-30 13:02:53.044456983 +0100
>>> @@ -2036 +2035,0 @@ GLIBC_2.27 wcstof64x_l F
>>> -GLIBC_2.28 fcntl F
>>>
>>> but i don't know if hurd is supposed to work...
>>>
>>
>> I will look into it.
>>
> 
> If you don't have time to look into this please put this on the
> release blocker list for 2.28 so we can look into this.
> 
> Having an ABI failure like this for release would be bad.
> 
> Thanks!
> 
> Cheers,
> Carlos.
> 

Sorry, I forgot to sent a [committed] message.  I already fixed it 
upstream [1].

[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=7279af007c420a9d5f88a6909d11e7cb712c16a4