netdev - Re: [PATCH bpf-next] tools/bpf: check precise {func,line,jited_line}_info_rec_size in test

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Date:   Tue, 18 Dec 2018 14:53:25 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Yonghong Song <yhs@...com>, ast@...com, netdev@...r.kernel.org
Cc:     kernel-team@...com
Subject: Re: [PATCH bpf-next] tools/bpf: check precise
 {func,line,jited_line}_info_rec_size in test_btf

On 12/18/2018 02:31 AM, Yonghong Song wrote:
> Current btf func_info, line_info and jited_line are designed to be
> extensible. The record sizes for {func,line}_info are passed to kernel,
> and the record sizes for {func,line,jited_line}_info are returned to
> userspace during bpf_prog_info query.
> 
> In bpf selftests test_btf.c, when testing whether kernel returns
> a legitimate {func,line, jited_line)_info rec_size, the test only
> compares to the minimum allowed size. If the returned rec_size is smaller
> than the minimum allowed size, it is considered incorrect.
> The minimum allowed size for these three info sizes are equal to
> current value of sizeof(struct bpf_func_info), sizeof(struct bpf_line_info)
> and sizeof(__u64).
> 
> The original thinking was that in the future when rec_size is increased
> in kernel, the same test should run correctly. But this sacrificed
> the precision of testing under the very kernel the test is shipped with,
> and bpf selftest is typically run with the same repo kernel.
> 
> So this patch changed the testing of rec_size such that the
> kernel returned value should be equal to the size defined by
> tools uapi header bpf.h which syncs with kernel uapi header.
> 
> Martin discovered a bug in one of rec_size comparisons.
> Instead of comparing to minimum func_info rec_size 8, it compares to 4.
> This patch fixed that issue as well.
> 
> Fixes: 999d82cbc044 ("tools/bpf: enhance test_btf file testing to test func info")
> Fixes: 05687352c600 ("bpf: Refactor and bug fix in test_func_type in test_btf.c")
> Fixes: 4d6304c76355 ("bpf: Add unit tests for bpf_line_info")
> Suggested-by: Martin KaFai Lau <kafai@...com>
> Acked-by: Martin KaFai Lau <kafai@...com>
> Signed-off-by: Yonghong Song <yhs@...com>

Applied to bpf-next, thanks!