Linux Extended-stat system call

[Florian Weimer]

On 06/22/2016 06:03 PM, Arnd Bergmann wrote:
> On Wednesday, June 22, 2016 5:03:43 PM CEST Florian Weimer wrote:
>> On 06/22/2016 04:08 PM, David Howells wrote:
>>
>>> One thing I would like to do is make it so that stat() can use it with minimal
>>> effort.
>>
>> Why is this an important goal?
>>
>> Existing architectures will keep using the old system call for the
>> legacy stat interfaces.  New architectures can use the new system call,
>> but will probably have a different definition of struct stat (which
>> might well be guided by our experience with the extended stat interface).
>
> For the y2038 work, we have to replace the stat system call on all 32-bit
> architectures (and mips64, which uses 32-bit st_mtime). We can do this
> by adding just a new version of the fstatat() syscall to the kernel that
> matches the ABI of the 64-bit architectures, or by mapping everything
> onto the new xstat.
>
> Adding just one new syscall entry point instead of two simplifies the
> kernel implementation quite a bit, but if there are good reasons for
> still providing a new fstatat version, we could do that too.

Thanks for providing the background.

If we can get all the data with a single system call, I don't think it 
matters much were we do the translation.  A single new system call is 
less work for strace, so I assume that's the way to go.

Florian