diff options
| author | Eric Dumazet <edumazet@google.com> | 2017-08-31 04:53:42 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-08-31 11:57:37 -0700 |
| commit | 84ccac6e7854ebbfb56d2fc6d5bef9be49bb304c (patch) | |
| tree | 86577241d7a33a02dc714cbfd0c32fa7c19ebd8d | |
| parent | 3edcf18ec2a8665fec060a05535fca6be16a61de (diff) | |
| download | linux-next-84ccac6e7854ebbfb56d2fc6d5bef9be49bb304c.tar.gz | |
x86: bpf_jit: small optimization in emit_bpf_tail_call()
Saves 4 bytes replacing following instructions :
lea rax, [rsi + rdx * 8 + offsetof(...)]
mov rax, qword ptr [rax]
cmp rax, 0
by :
mov rax, [rsi + rdx * 8 + offsetof(...)]
test rax, rax
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 8194696e2805..8c9573660d51 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -287,7 +287,7 @@ static void emit_bpf_tail_call(u8 **pprog) EMIT4(0x48, 0x8B, 0x46, /* mov rax, qword ptr [rsi + 16] */ offsetof(struct bpf_array, map.max_entries)); EMIT3(0x48, 0x39, 0xD0); /* cmp rax, rdx */ -#define OFFSET1 47 /* number of bytes to jump */ +#define OFFSET1 43 /* number of bytes to jump */ EMIT2(X86_JBE, OFFSET1); /* jbe out */ label1 = cnt; @@ -296,21 +296,20 @@ static void emit_bpf_tail_call(u8 **pprog) */ EMIT2_off32(0x8B, 0x85, 36); /* mov eax, dword ptr [rbp + 36] */ EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */ -#define OFFSET2 36 +#define OFFSET2 32 EMIT2(X86_JA, OFFSET2); /* ja out */ label2 = cnt; EMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */ EMIT2_off32(0x89, 0x85, 36); /* mov dword ptr [rbp + 36], eax */ /* prog = array->ptrs[index]; */ - EMIT4_off32(0x48, 0x8D, 0x84, 0xD6, /* lea rax, [rsi + rdx * 8 + offsetof(...)] */ + EMIT4_off32(0x48, 0x8B, 0x84, 0xD6, /* mov rax, [rsi + rdx * 8 + offsetof(...)] */ offsetof(struct bpf_array, ptrs)); - EMIT3(0x48, 0x8B, 0x00); /* mov rax, qword ptr [rax] */ /* if (prog == NULL) * goto out; */ - EMIT4(0x48, 0x83, 0xF8, 0x00); /* cmp rax, 0 */ + EMIT3(0x48, 0x85, 0xC0); /* test rax,rax */ #define OFFSET3 10 EMIT2(X86_JE, OFFSET3); /* je out */ label3 = cnt; |