| commit | 606c88a86c77fa27cb4eac899ddced9092825bea | |
| author | Daniel Borkmann <daniel@iogearbox.net> | |
| Thu, 17 Dec 2015 22:51:56 +0000 (17 23:51 +0100) | ||
| committer | David S. Miller <davem@davemloft.net> | |
| Fri, 18 Dec 2015 21:04:51 +0000 (18 16:04 -0500) | ||
| tree | 6912e097e8e74ca15f8567739eb4b215845f6bc7 | treesnapshot (tar.gz zip) |
| parent | 23bf88078afdb8f9b8071dd9f32754ebab7ba3dc | commitdiff |
bpf, x86: detect/optimize loading 0 immediates
When sometimes structs or variables need to be initialized/'memset' to 0 in
an eBPF C program, the x86 BPF JIT converts this to use immediates. We can
however save a couple of bytes (f.e. even up to 7 bytes on a single emmission
of BPF_LD | BPF_IMM | BPF_DW) in the image by detecting such case and use xor
on the dst register instead.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
When sometimes structs or variables need to be initialized/'memset' to 0 in
an eBPF C program, the x86 BPF JIT converts this to use immediates. We can
however save a couple of bytes (f.e. even up to 7 bytes on a single emmission
of BPF_LD | BPF_IMM | BPF_DW) in the image by detecting such case and use xor
on the dst register instead.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
| arch/x86/net/bpf_jit_comp.c | diffblobblamehistory |