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From:   Sergei Trofimovich <slyich@gmail.com>
To:     bpf@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org,
        Sergei Trofimovich <slyich@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>,
        Yonghong Song <yonghong.song@linux.dev>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>
Subject: [PATCH] tools/lib/bpf: add pr_warn() to more -EINVAL cases
Date:   Thu,  7 Dec 2023 18:09:19 +0000
Message-ID: <20231207180919.2379718-1-slyich@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Before the change on `i686-linux` `systemd` build failed as:

    $ bpftool gen object src/core/bpf/socket_bind/socket-bind.bpf.o src/core/bpf/socket_bind/socket-bind.bpf.unstripped.o
    Error: failed to link 'src/core/bpf/socket_bind/socket-bind.bpf.unstripped.o': Invalid argument (22)

After the change it fails as:

    $ bpftool gen object src/core/bpf/socket_bind/socket-bind.bpf.o src/core/bpf/socket_bind/socket-bind.bpf.unstripped.o
    libbpf: ELF section #9 has inconsistent alignment in src/core/bpf/socket_bind/socket-bind.bpf.unstripped.o
    Error: failed to link 'src/core/bpf/socket_bind/socket-bind.bpf.unstripped.o': Invalid argument (22)

Now it's slightly easier to figure out what is wrong with an ELF file.

CC: Alexei Starovoitov <ast@kernel.org>
CC: Daniel Borkmann <daniel@iogearbox.net>
CC: Andrii Nakryiko <andrii@kernel.org>
CC: Martin KaFai Lau <martin.lau@linux.dev>
CC: Song Liu <song@kernel.org>
CC: Yonghong Song <yonghong.song@linux.dev>
CC: John Fastabend <john.fastabend@gmail.com>
CC: KP Singh <kpsingh@kernel.org>
CC: Stanislav Fomichev <sdf@google.com>
CC: Hao Luo <haoluo@google.com>
CC: Jiri Olsa <jolsa@kernel.org>
CC: bpf@vger.kernel.org
Signed-off-by: Sergei Trofimovich <slyich@gmail.com>
---
 tools/lib/bpf/linker.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index 5ced96d99f8c..71bb4916b762 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -719,13 +719,22 @@ static int linker_sanity_check_elf(struct src_obj *obj)
 			return -EINVAL;
 		}
 
-		if (sec->shdr->sh_addralign && !is_pow_of_2(sec->shdr->sh_addralign))
+		if (sec->shdr->sh_addralign && !is_pow_of_2(sec->shdr->sh_addralign)) {
+			pr_warn("ELF section #%zu alignment is non pow-of-2 alignment in %s\n",
+				sec->sec_idx, obj->filename);
 			return -EINVAL;
-		if (sec->shdr->sh_addralign != sec->data->d_align)
+		}
+		if (sec->shdr->sh_addralign != sec->data->d_align) {
+			pr_warn("ELF section #%zu has inconsistent alignment in %s\n",
+				sec->sec_idx, obj->filename);
 			return -EINVAL;
+		}
 
-		if (sec->shdr->sh_size != sec->data->d_size)
+		if (sec->shdr->sh_size != sec->data->d_size) {
+			pr_warn("ELF section #%zu has inconsistent section size in %s\n",
+				sec->sec_idx, obj->filename);
 			return -EINVAL;
+		}
 
 		switch (sec->shdr->sh_type) {
 		case SHT_SYMTAB:
-- 
2.42.0