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Marchesi" , Vineet Gupta , Yonghong Song Subject: [PATCH bpf-next v4 05/17] selftests/bpf: Cover unknown BTF header-extension bytes in bpftool C dumps Date: Thu, 5 Nov 2026 10:58:33 -0700 Message-ID: <20261105175845.30357-6-ihor.solodrai@linux.dev> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261105175845.30357-1-ihor.solodrai@linux.dev> References: <20261105175845.30357-1-ihor.solodrai@linux.dev> X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit libbpf can parse BTF whose header carries unknown nonzero extension bytes, such as BTF from a newer kernel, but refuses to modify it. bpftool dumps C through a split BTF over the input, so that it can annotate the dump without modifying the input. Check that a C dump of such BTF matches the dump of the same BTF without the extension bytes. Signed-off-by: Ihor Solodrai --- .../bpf/prog_tests/bpftool_btf_dump.c | 42 +++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/bpftool_btf_dump.c b/tools/testing/selftests/bpf/prog_tests/bpftool_btf_dump.c index 80e8e435d702..0cfff1b96666 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpftool_btf_dump.c +++ b/tools/testing/selftests/bpf/prog_tests/bpftool_btf_dump.c @@ -57,6 +57,42 @@ static struct btf *mk_btf(void) return btf; } +/* mk_btf() with a nonzero byte in an unknown header extension */ +static struct btf *mk_hdr_extra_btf(void) +{ + struct btf *btf, *ext_btf = NULL; + const __u32 extra_sz = 4; + __u32 hdr_len, sz; + const void *raw; + char *ext; + + btf = mk_btf(); + if (!btf) + return NULL; + + raw = btf__raw_data(btf, &sz); + if (!ASSERT_OK_PTR(raw, "raw_data")) + goto out; + + hdr_len = ((const struct btf_header *)raw)->hdr_len; + + ext = calloc(1, sz + extra_sz); + if (!ASSERT_OK_PTR(ext, "alloc_ext")) + goto out; + + memcpy(ext, raw, hdr_len); + ext[hdr_len] = 0xA5; /* any nonzero value */ + memcpy(ext + hdr_len + extra_sz, raw + hdr_len, sz - hdr_len); + ((struct btf_header *)ext)->hdr_len = hdr_len + extra_sz; + + ext_btf = btf__new(ext, sz + extra_sz); + ASSERT_OK_PTR(ext_btf, "btf_new_ext"); + free(ext); +out: + btf__free(btf); + return ext_btf; +} + static struct btf *mk_loc_btf(void) { struct btf *btf; @@ -283,6 +319,12 @@ void test_bpftool_btf_dump(void) unlink(path); } + if (!btf_to_tmpfile(mk_hdr_extra_btf, path)) { + if (test__start_subtest("hdr_extra")) + test_dump(path, true); + unlink(path); + } + if (!btf_to_tmpfile(mk_loc_btf, path)) { if (test__start_subtest("loc_dump")) test_loc_dump(path); -- 2.56.0