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author | Stanislav Fomichev <sdf@google.com> | 2019-11-27 14:57:59 -0800 |
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committer | Daniel Borkmann <daniel@iogearbox.net> | 2019-11-29 10:18:57 +0100 |
commit | df786c9b947639aedbc7bb44b5dae2a7824af360 (patch) | |
tree | c47ad5f82c960333514486f3b0b3572ffae569f5 /tools | |
parent | ce27709b8162e5c501bc54292b8bf6bdecc4bbd4 (diff) | |
download | linux-df786c9b947639aedbc7bb44b5dae2a7824af360.tar.bz2 |
bpf: Force .BTF section start to zero when dumping from vmlinux
While trying to figure out why fentry_fexit selftest doesn't pass for me
(old pahole, broken BTF), I found out that my latest patch can break vmlinux
.BTF generation. objcopy preserves section start when doing --only-section,
so there is a chance (depending on where pahole inserts .BTF section) to
have leading empty zeroes. Let's explicitly force section offset to zero.
Before:
$ objcopy --set-section-flags .BTF=alloc -O binary \
--only-section=.BTF vmlinux .btf.vmlinux.bin
$ xxd .btf.vmlinux.bin | head -n1
00000000: 0000 0000 0000 0000 0000 0000 0000 0000 ................
After:
$ objcopy --change-section-address .BTF=0 \
--set-section-flags .BTF=alloc -O binary \
--only-section=.BTF vmlinux .btf.vmlinux.bin
$ xxd .btf.vmlinux.bin | head -n1
00000000: 9feb 0100 1800 0000 0000 0000 80e1 1c00 ................
^BTF magic
As part of this change, I'm also dropping '2>/dev/null' from objcopy
invocation to be able to catch possible other issues (objcopy doesn't
produce any warnings for me anymore, it did before with --dump-section).
Fixes: da5fb18225b4 ("bpf: Support pre-2.25-binutils objcopy for vmlinux BTF")
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191127225759.39923-1-sdf@google.com
Diffstat (limited to 'tools')
0 files changed, 0 insertions, 0 deletions