From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Alexei Starovoitov , Daniel Borkmann , "David S. Miller" Subject: [PATCH 4.9 59/66] x86: bpf_jit: small optimization in emit_bpf_tail_call() Date: Mon, 29 Jan 2018 13:57:23 +0100 Message-Id: <20180129123842.996759510@linuxfoundation.org> In-Reply-To: <20180129123839.842860149@linuxfoundation.org> References: <20180129123839.842860149@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ upstream commit 84ccac6e7854ebbfb56d2fc6d5bef9be49bb304c ] 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 Cc: Alexei Starovoitov Cc: Daniel Borkmann Acked-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- arch/x86/net/bpf_jit_comp.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -281,7 +281,7 @@ static void emit_bpf_tail_call(u8 **ppro 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; @@ -290,21 +290,20 @@ static void emit_bpf_tail_call(u8 **ppro */ EMIT2_off32(0x8B, 0x85, -STACKSIZE + 36); /* mov eax, dword ptr [rbp - 516] */ 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, -STACKSIZE + 36); /* mov dword ptr [rbp - 516], 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;