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| author | Alexei Starovoitov <[email protected]> | 2020-03-11 00:39:06 +0000 |
|---|---|---|
| committer | Daniel Borkmann <[email protected]> | 2020-03-11 13:07:32 +0000 |
| commit | 13fac1d851e09109096b5862bf37c3da6908fb48 (patch) | |
| tree | 927815f0128976e44e7f0435f52b91dd348ca4ea /tools/bpf/bpftool/prog.c | |
| parent | bpf: Add bpf_link_new_file that doesn't install FD (diff) | |
| download | kernel-13fac1d851e09109096b5862bf37c3da6908fb48.tar.gz kernel-13fac1d851e09109096b5862bf37c3da6908fb48.zip | |
bpf: Fix trampoline generation for fmod_ret programs
fmod_ret progs are emitted as:
start = __bpf_prog_enter();
call fmod_ret
*(u64 *)(rbp - 8) = rax
__bpf_prog_exit(, start);
test eax, eax
jne do_fexit
That 'test eax, eax' is working by accident. The compiler is free to use rax
inside __bpf_prog_exit() or inside functions that __bpf_prog_exit() is calling.
Which caused "test_progs -t modify_return" to sporadically fail depending on
compiler version and kconfig. Fix it by using 'cmp [rbp - 8], 0' instead of
'test eax, eax'.
Fixes: ae24082331d9 ("bpf: Introduce BPF_MODIFY_RETURN")
Reported-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Acked-by: KP Singh <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
Diffstat (limited to 'tools/bpf/bpftool/prog.c')
0 files changed, 0 insertions, 0 deletions