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authorEric Dumazet <edumazet@google.com>2017-08-31 04:53:42 -0700
committerDavid S. Miller <davem@davemloft.net>2017-08-31 11:57:37 -0700
commit84ccac6e7854ebbfb56d2fc6d5bef9be49bb304c (patch)
tree86577241d7a33a02dc714cbfd0c32fa7c19ebd8d /arch/x86
parent3edcf18ec2a8665fec060a05535fca6be16a61de (diff)
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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>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/net/bpf_jit_comp.c9
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;