{"id":808217,"url":"http://patchwork.ozlabs.org/api/patches/808217/?format=json","web_url":"http://patchwork.ozlabs.org/project/netdev/patch/1504180422.15310.12.camel@edumazet-glaptop3.roam.corp.google.com/","project":{"id":7,"url":"http://patchwork.ozlabs.org/api/projects/7/?format=json","name":"Linux network development","link_name":"netdev","list_id":"netdev.vger.kernel.org","list_email":"netdev@vger.kernel.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<1504180422.15310.12.camel@edumazet-glaptop3.roam.corp.google.com>","list_archive_url":null,"date":"2017-08-31T11:53:42","name":"[net-next] x86: bpf_jit: small optimization in emit_bpf_tail_call()","commit_ref":null,"pull_url":null,"state":"accepted","archived":true,"hash":"05407d8143fc850a1d94c72d430e6dc2ab83f80e","submitter":{"id":2404,"url":"http://patchwork.ozlabs.org/api/people/2404/?format=json","name":"Eric Dumazet","email":"eric.dumazet@gmail.com"},"delegate":{"id":34,"url":"http://patchwork.ozlabs.org/api/users/34/?format=json","username":"davem","first_name":"David","last_name":"Miller","email":"davem@davemloft.net"},"mbox":"http://patchwork.ozlabs.org/project/netdev/patch/1504180422.15310.12.camel@edumazet-glaptop3.roam.corp.google.com/mbox/","series":[{"id":808,"url":"http://patchwork.ozlabs.org/api/series/808/?format=json","web_url":"http://patchwork.ozlabs.org/project/netdev/list/?series=808","date":"2017-08-31T11:53:42","name":"[net-next] x86: bpf_jit: small optimization in emit_bpf_tail_call()","version":1,"mbox":"http://patchwork.ozlabs.org/series/808/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/808217/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/808217/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":"patchwork-incoming@ozlabs.org","Delivered-To":"patchwork-incoming@ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=none (mailfrom) smtp.mailfrom=vger.kernel.org\n\t(client-ip=209.132.180.67; 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\n\tThu, 31 Aug 2017 04:53:45 -0700 (PDT)","Message-ID":"<1504180422.15310.12.camel@edumazet-glaptop3.roam.corp.google.com>","Subject":"[PATCH net-next] x86: bpf_jit: small optimization in\n\temit_bpf_tail_call()","From":"Eric Dumazet ","To":"David Miller ","Cc":"netdev , Alexei Starovoitov ,\n\tDaniel Borkmann ","Date":"Thu, 31 Aug 2017 04:53:42 -0700","Content-Type":"text/plain; charset=\"UTF-8\"","X-Mailer":"Evolution 3.10.4-0ubuntu2 ","Mime-Version":"1.0","Content-Transfer-Encoding":"7bit","Sender":"netdev-owner@vger.kernel.org","Precedence":"bulk","List-ID":"","X-Mailing-List":"netdev@vger.kernel.org"},"content":"From: Eric Dumazet \n\nSaves 4 bytes replacing following instructions :\n\nlea rax, [rsi + rdx * 8 + offsetof(...)] \nmov rax, qword ptr [rax]\ncmp rax, 0\n\nby :\n\nmov rax, [rsi + rdx * 8 + offsetof(...)] \ntest rax, rax\n\nSigned-off-by: Eric Dumazet \nCc: Alexei Starovoitov \nCc: Daniel Borkmann \n---\n arch/x86/net/bpf_jit_comp.c | 9 ++++-----\n 1 file changed, 4 insertions(+), 5 deletions(-)","diff":"diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c\nindex 8194696e2805852a8246bf1db2a5862d5758f76b..7af5ee584bf8546f3c1b92df9d9f513416f2089d 100644\n--- a/arch/x86/net/bpf_jit_comp.c\n+++ b/arch/x86/net/bpf_jit_comp.c\n@@ -287,7 +287,7 @@ static void emit_bpf_tail_call(u8 **pprog)\n \tEMIT4(0x48, 0x8B, 0x46, /* mov rax, qword ptr [rsi + 16] */\n \t offsetof(struct bpf_array, map.max_entries));\n \tEMIT3(0x48, 0x39, 0xD0); /* cmp rax, rdx */\n-#define OFFSET1 47 /* number of bytes to jump */\n+#define OFFSET1 43 /* number of bytes to jump */\n \tEMIT2(X86_JBE, OFFSET1); /* jbe out */\n \tlabel1 = cnt;\n \n@@ -296,21 +296,20 @@ static void emit_bpf_tail_call(u8 **pprog)\n \t */\n \tEMIT2_off32(0x8B, 0x85, 36); /* mov eax, dword ptr [rbp + 36] */\n \tEMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */\n-#define OFFSET2 36\n+#define OFFSET2 32\n \tEMIT2(X86_JA, OFFSET2); /* ja out */\n \tlabel2 = cnt;\n \tEMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */\n \tEMIT2_off32(0x89, 0x85, 36); /* mov dword ptr [rbp + 36], eax */\n \n \t/* prog = array->ptrs[index]; */\n-\tEMIT4_off32(0x48, 0x8D, 0x84, 0xD6, /* lea rax, [rsi + rdx * 8 + offsetof(...)] */\n+\tEMIT4_off32(0x48, 0x8B, 0x84, 0xD6, /* mov rax, [rsi + rdx * 8 + offsetof(...)] */\n \t\t offsetof(struct bpf_array, ptrs));\n-\tEMIT3(0x48, 0x8B, 0x00); /* mov rax, qword ptr [rax] */\n \n \t/* if (prog == NULL)\n \t * goto out;\n \t */\n-\tEMIT4(0x48, 0x83, 0xF8, 0x00); /* cmp rax, 0 */\n+\tEMIT3(0x48, 0x85, 0xC0);\t\t /* test rax,rax */\n #define OFFSET3 10\n \tEMIT2(X86_JE, OFFSET3); /* je out */\n \tlabel3 = cnt;\n","prefixes":["net-next"]}