[LTP] [PATCH v2] syscalls: add syscall syncfs test

Steve Muckle smuckle@google.com
Wed Feb 20 00:15:40 CET 2019

On 02/18/2019 03:57 AM, Cyril Hrubis wrote:
>> For tests in testcases/kernel/syscalls, should the tests typically
>> directly call the syscall? I'd think this is preferable to the use of C
>> library wrappers as these tests (by their location in the tree) seem to
>> be focused on the syscall functionality in the kernel.
> My take on this is that for a functional testing we really have to test
> the kernel together with the library that wraps the syscalls because
> otherwise bugs are bound to happen such as these:
> https://sourceware.org/bugzilla/show_bug.cgi?id=23069
> https://sourceware.org/bugzilla/show_bug.cgi?id=23579
> And I always cared about syscalls being correct on the C library level.
> I guess that for most of the syscalls that are just thin wrappers it
> does not matter since these just prepare the parameters and jump to the
> kernel, but in certain cases libc does quite a lot of work which is
> sometimes complex code I do not want to replicate that unless really
> needed. And with that I think that it's actually much easier to go with
> the libc API whenever possible rather than reviewing the libc code each
> time we write a testcase.
> Does that sound reasonable to you?

Sure. My concern is being able to test syscalls in Android where the C 
library may not have some wrappers. So far these have all been cases 
where one can just replace the library call with the direct syscall, as 
a number of recent patches have done. If I run into a case where more 
substantial library support is needed maybe we'll just have to focus on 
getting that into bionic or look at other options.


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