Re: bpf selftests and page size
From: Andrii Nakryiko <hidden>
Date: 2021-03-03 22:57:33
On Wed, Mar 3, 2021 at 2:40 AM Yauheni Kaliuta [off-list ref] wrote:
Hi! On Tue, Mar 2, 2021 at 7:08 AM Andrii Nakryiko [off-list ref] wrote:quoted
On Mon, Mar 1, 2021 at 1:02 AM Yauheni Kaliuta [off-list ref] wrote:quoted
Bunch of bpf selftests actually depends of page size and has it hardcoded to 4K. That causes failures if page shift is configured to values other than 12. It looks as a known issue since for the userspace parts sysconf(_SC_PAGE_SIZE) is used, but what would be the correct way to export it to bpf programs?Given PAGE_SIZE and PAGE_SHIFT are just #defines, the only way seems to be to pass it from the user-space as a read-only variable.Compile-time? Just to make sure we are on the same page, the tests may look like https://github.com/torvalds/linux/blob/master/tools/testing/selftests/bpf/progs/map_ptr_kern.c#L638
Oh, if it's about ringbuf, then why not just bump its size to 64KB or something even bigger. I thought that you were referring to some BPF code that needs to do some calculations based on PAGE_SIZE in runtime.
-- WBR, Yauheni