[PATCH v8] linux: Add openat2 (BZ 31664)

[Adhemerval Zanella Netto]

On 08/12/25 11:18, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> The openat2 syscall was added on Linux 5.6, as an extension of openat.
>> Unlike other open-like functions, the kernel only provides the LFS
>> variant (so files larger than 4GB always succeed, unlike other
>> functions with an offset larger than off_t).  Also, similar to other
>> open functions, the new symbol is a cancellable entrypoint.
>>
>> The test case added only stress tests for some of the syscalls' provided
>> functionality, and it is based on an existing kernel self-test.
>>
>> A fortify wrapper is added to verify the argument size if not larger
>> than the current support open_how struct.
>>
>> Gnulib added an openat2 module, which uses read-only for the open_how
>> argument [1].  There is no clear indication whether the kernel will
>> indeed use the argument as in-out, how it would do so, or for which
>> kind of functionality [2]. Also, adding a potentially different prototype
>> than gnulib only would add extra unnecessary friction and extra
>> wrappers to handle it.
>>
>> Checked on x86_64-linux-gnu and aarch64-linux-gnu.
>>
>> [1] https://gitweb.git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commit;h=0b97ffdf32bdab909d02449043447237273df75e
>> [2] https://sourceware.org/pipermail/libc-alpha/2025-September/169740.html
>>
>> Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> 
> Adhemerval, Carlos, is this patch accepted, or does it need further
> review?

I think it should be ok for inclusion, Carlos pointed out some minor
typos in the v7 [1] and stated that I should keep the RB.

I will commit this shortly.

[1] https://sourceware.org/pipermail/libc-alpha/2025-November/172687.html