From: Tony Ambardar <tony.ambardar@gmail.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>
Cc: Tony Ambardar <Tony.Ambardar@gmail.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-arch@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH bpf v1 3/3] libbpf: fix native endian assumption when parsing BTF
Date: Sat, 19 Sep 2020 22:01:35 -0700 [thread overview]
Message-ID: <90f81508ecc57bc0da318e0fe0f45cfe49b17ea7.1600417359.git.Tony.Ambardar@gmail.com> (raw)
In-Reply-To: <cover.1600417359.git.Tony.Ambardar@gmail.com>
Code in btf__parse_raw() fails to detect raw BTF of non-native endianness
and assumes it must be ELF data, which then fails to parse as ELF and
yields a misleading error message:
root:/# bpftool btf dump file /sys/kernel/btf/vmlinux
libbpf: failed to get EHDR from /sys/kernel/btf/vmlinux
For example, this could occur after cross-compiling a BTF-enabled kernel
for a target with non-native endianness, which is currently unsupported.
Check for correct endianness and emit a clearer error message:
root:/# bpftool btf dump file /sys/kernel/btf/vmlinux
libbpf: non-native BTF endianness is not supported
Fixes: 94a1fedd63ed ("libbpf: Add btf__parse_raw() and generic btf__parse() APIs")
Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>
---
tools/lib/bpf/btf.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 7dfca7016aaa..6bdbc389b493 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -659,6 +659,12 @@ struct btf *btf__parse_raw(const char *path)
err = -EIO;
goto err_out;
}
+ if (magic == __bswap_16(BTF_MAGIC)) {
+ /* non-native endian raw BTF */
+ pr_warn("non-native BTF endianness is not supported\n");
+ err = -LIBBPF_ERRNO__ENDIAN;
+ goto err_out;
+ }
if (magic != BTF_MAGIC) {
/* definitely not a raw BTF */
err = -EPROTO;
--
2.25.1
next prev parent reply other threads:[~2020-09-20 5:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-20 5:01 [PATCH bpf v1 0/3] fix BTF usage on embedded systems Tony Ambardar
2020-09-20 5:01 ` [PATCH bpf v1 1/3] bpf: fix sysfs export of empty BTF section Tony Ambardar
2020-09-21 15:44 ` John Fastabend
2020-09-21 19:21 ` Andrii Nakryiko
2020-09-20 5:01 ` [PATCH bpf v1 2/3] bpf: prevent .BTF section elimination Tony Ambardar
2020-09-21 15:45 ` John Fastabend
2020-09-20 5:01 ` Tony Ambardar [this message]
2020-09-21 15:46 ` [PATCH bpf v1 3/3] libbpf: fix native endian assumption when parsing BTF John Fastabend
2020-09-21 19:24 ` [PATCH bpf v1 0/3] fix BTF usage on embedded systems Andrii Nakryiko
2020-09-21 20:52 ` Daniel Borkmann
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