On 2020-04-28, Cyril Hrubis wrote: > Hi! > > > > commit: ce436509a8e109330c56bb4d8ec87d258788f5f4 ("[PATCH v4 2/3] fs: openat2: Extend open_how to allow userspace-selected fds") > > > > url: https://github.com/0day-ci/linux/commits/Josh-Triplett/Support-userspace-selected-fds/20200414-102939 > > > > base: https://git.kernel.org/cgit/linux/kernel/git/shuah/linux-kselftest.git next > > > > > > This commit adds fd parameter to the how structure where LTP test was > > > previously passing garbage, which obviously causes the difference in > > > errno. > > > > > > This could be safely ignored for now, if the patch gets merged the test > > > needs to be updated. > > > > It wouldn't be a bad idea to switch the test to figure out the ksize of > > the struct, so that you only add bad padding after that. But then again, > > this would be a bit ugly -- having CHECK_FIELDS would make this simpler. > > Any pointers how can be the size figured out without relying on the > E2BIG we are testing for? Does the kernel export it somewhere? No, you would have to effectively binary search on -E2BIG at the moment. CHECK_FIELDS is a proposal I have which would allow you to get get the size of the in-kernel struct, but it's still a proposal. In theory you could get the size through BTF, but it's probably more effort than it's worth to implement that. -- Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH