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Date: Sat, 19 Sep 2020 22:01:35 -0700 From: Tony Ambardar <tony.ambardar@...il.com> To: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net> Cc: Tony Ambardar <Tony.Ambardar@...il.com>, netdev@...r.kernel.org, bpf@...r.kernel.org, linux-arch@...r.kernel.org, Arnd Bergmann <arnd@...db.de> Subject: [PATCH bpf v1 3/3] libbpf: fix native endian assumption when parsing BTF 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@...il.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
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