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Wed, 30 Sep 2026 20:43:11 -0700 (PDT) From: Luis Vieira Date: Thu, 01 Oct 2026 00:42:58 -0300 Subject: [PATCH bpf-next v2 1/2] libbpf: Fix struct and union zero detection in BTF dumper Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261001-libbpf-btf-enodata-fix-v2-1-89f6e8a0240e@gmail.com> References: <20261001-libbpf-btf-enodata-fix-v2-0-89f6e8a0240e@gmail.com> In-Reply-To: <20261001-libbpf-btf-enodata-fix-v2-0-89f6e8a0240e@gmail.com> To: Andrii Nakryiko , Eduard Zingerman , Ihor Solodrai , Alexei Starovoitov , Daniel Borkmann , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Shuah Khan Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Luis Vieira X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1790826180; l=1187; i=luisflavieira@gmail.com; s=20260913; h=from:subject:message-id; bh=oUeXwTCQbEyPdKNvTT+R4vw8lmHVoLHGeElv1oBHK1E=; b=EDnrT6kKkUuj7s1mRM9dxT3GkXe/76ILO4Zdju1bN1vq6r5P5Wc85VUWqdrME4mVNlgX8AKMN wCnS8zZzFJWBIMLZyZLaZIEwCpummvyQ9uO1Eit78HMurUNwbb3V+B/ X-Developer-Key: i=luisflavieira@gmail.com; a=ed25519; pk=98MeC/NdrC6ah7zYpPnkWiQIoyj62iUP/rNuV3esCW4= btf_dump_type_data_check_zero() uses -ENODATA to indicate that a value is zero. The array path handles this sentinel correctly, but the struct and union path compares the return value against positive ENODATA. As a result, the member loop returns after examining its first member. A nested struct or union whose first member is zero can therefore be treated as entirely zero even when a later member is non-zero. Compare against -ENODATA so zero members are skipped while looking for a non-zero member. Signed-off-by: Luis Vieira --- tools/lib/bpf/btf_dump.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index 996e61b5f11f..ad43bbd3b442 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -2564,7 +2564,7 @@ static int btf_dump_type_data_check_zero(struct btf_dump *d, bit_sz = btf_member_bitfield_size(t, i); err = btf_dump_type_data_check_zero(d, mtype, m->type, data + moffset / 8, moffset % 8, bit_sz); - if (err != ENODATA) + if (err != -ENODATA) return err; } return -ENODATA; -- 2.43.0