diff options
| author | Daniel Borkmann <daniel@iogearbox.net> | 2016-02-19 23:05:27 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-02-21 22:07:11 -0500 |
| commit | 6205b9cf200d1c3dda5491666ddc33e7b70fe469 (patch) | |
| tree | 78c48c223c2b45253361e929a1bffc291dd16925 /net/core | |
| parent | 2f72959a9c1260ade234f353ccca91118151af66 (diff) | |
| download | linux-6205b9cf200d1c3dda5491666ddc33e7b70fe469.tar.bz2 | |
bpf: don't emit mov A,A on return
While debugging with bpf_jit_disasm I noticed emissions of 'mov %eax,%eax',
and found that this comes from BPF_RET | BPF_A translations from classic
BPF. Emitting this is unnecessary as BPF_REG_A is mapped into BPF_REG_0
already, therefore only emit a mov when immediates are used as return value.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/filter.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 8a0b8c3eb189..a3aba15a8025 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -530,12 +530,14 @@ do_pass: *insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_TMP); break; - /* RET_K, RET_A are remaped into 2 insns. */ + /* RET_K is remaped into 2 insns. RET_A case doesn't need an + * extra mov as BPF_REG_0 is already mapped into BPF_REG_A. + */ case BPF_RET | BPF_A: case BPF_RET | BPF_K: - *insn++ = BPF_MOV32_RAW(BPF_RVAL(fp->code) == BPF_K ? - BPF_K : BPF_X, BPF_REG_0, - BPF_REG_A, fp->k); + if (BPF_RVAL(fp->code) == BPF_K) + *insn++ = BPF_MOV32_RAW(BPF_K, BPF_REG_0, + 0, fp->k); *insn = BPF_EXIT_INSN(); break; |