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From: Brendan Jackman <jackmanb@google.com>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>, Yonghong Song <yhs@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	KP Singh <kpsingh@chromium.org>,
	Florent Revest <revest@chromium.org>,
	linux-kernel@vger.kernel.org, Jann Horn <jannh@google.com>,
	Brendan Jackman <jackmanb@google.com>
Subject: [PATCH bpf-next v4 03/11] bpf: x86: Factor out a lookup table for some ALU opcodes
Date: Mon,  7 Dec 2020 16:07:26 +0000	[thread overview]
Message-ID: <20201207160734.2345502-4-jackmanb@google.com> (raw)
In-Reply-To: <20201207160734.2345502-1-jackmanb@google.com>

A later commit will need to lookup a subset of these opcodes. To
avoid duplicating code, pull out a table.

The shift opcodes won't be needed by that later commit, but they're
already duplicated, so fold them into the table anyway.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 arch/x86/net/bpf_jit_comp.c | 33 +++++++++++++++------------------
 1 file changed, 15 insertions(+), 18 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 7106cfd10ba6..f0c98fd275e5 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -205,6 +205,18 @@ static u8 add_2reg(u8 byte, u32 dst_reg, u32 src_reg)
 	return byte + reg2hex[dst_reg] + (reg2hex[src_reg] << 3);
 }
 
+/* Some 1-byte opcodes for binary ALU operations */
+static u8 simple_alu_opcodes[] = {
+	[BPF_ADD] = 0x01,
+	[BPF_SUB] = 0x29,
+	[BPF_AND] = 0x21,
+	[BPF_OR] = 0x09,
+	[BPF_XOR] = 0x31,
+	[BPF_LSH] = 0xE0,
+	[BPF_RSH] = 0xE8,
+	[BPF_ARSH] = 0xF8,
+};
+
 static void jit_fill_hole(void *area, unsigned int size)
 {
 	/* Fill whole space with INT3 instructions */
@@ -862,15 +874,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 		case BPF_ALU64 | BPF_AND | BPF_X:
 		case BPF_ALU64 | BPF_OR | BPF_X:
 		case BPF_ALU64 | BPF_XOR | BPF_X:
-			switch (BPF_OP(insn->code)) {
-			case BPF_ADD: b2 = 0x01; break;
-			case BPF_SUB: b2 = 0x29; break;
-			case BPF_AND: b2 = 0x21; break;
-			case BPF_OR: b2 = 0x09; break;
-			case BPF_XOR: b2 = 0x31; break;
-			}
 			maybe_emit_mod(&prog, dst_reg, src_reg,
 				       BPF_CLASS(insn->code) == BPF_ALU64);
+			b2 = simple_alu_opcodes[BPF_OP(insn->code)];
 			EMIT2(b2, add_2reg(0xC0, dst_reg, src_reg));
 			break;
 
@@ -1050,12 +1056,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 			else if (is_ereg(dst_reg))
 				EMIT1(add_1mod(0x40, dst_reg));
 
-			switch (BPF_OP(insn->code)) {
-			case BPF_LSH: b3 = 0xE0; break;
-			case BPF_RSH: b3 = 0xE8; break;
-			case BPF_ARSH: b3 = 0xF8; break;
-			}
-
+			b3 = simple_alu_opcodes[BPF_OP(insn->code)];
 			if (imm32 == 1)
 				EMIT2(0xD1, add_1reg(b3, dst_reg));
 			else
@@ -1089,11 +1090,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 			else if (is_ereg(dst_reg))
 				EMIT1(add_1mod(0x40, dst_reg));
 
-			switch (BPF_OP(insn->code)) {
-			case BPF_LSH: b3 = 0xE0; break;
-			case BPF_RSH: b3 = 0xE8; break;
-			case BPF_ARSH: b3 = 0xF8; break;
-			}
+			b3 = simple_alu_opcodes[BPF_OP(insn->code)];
 			EMIT2(0xD3, add_1reg(b3, dst_reg));
 
 			if (src_reg != BPF_REG_4)
-- 
2.29.2.576.ga3fc446d84-goog


  parent reply	other threads:[~2020-12-07 16:09 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-07 16:07 [PATCH bpf-next v4 00/11] Atomics for eBPF Brendan Jackman
2020-12-07 16:07 ` [PATCH bpf-next v4 01/11] bpf: x86: Factor out emission of ModR/M for *(reg + off) Brendan Jackman
2020-12-07 21:04   ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 02/11] bpf: x86: Factor out emission of REX byte Brendan Jackman
2020-12-07 21:07   ` John Fastabend
2020-12-07 16:07 ` Brendan Jackman [this message]
2020-12-07 21:08   ` [PATCH bpf-next v4 03/11] bpf: x86: Factor out a lookup table for some ALU opcodes John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 04/11] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm Brendan Jackman
2020-12-07 21:56   ` John Fastabend
2020-12-08  9:26     ` Brendan Jackman
2020-12-09  5:40       ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 05/11] bpf: Move BPF_STX reserved field check into BPF_STX verifier code Brendan Jackman
2020-12-08  1:35   ` Yonghong Song
2020-12-08  5:13   ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 06/11] bpf: Add BPF_FETCH field / create atomic_fetch_add instruction Brendan Jackman
2020-12-08  1:41   ` Yonghong Song
2020-12-08  9:31     ` Brendan Jackman
2020-12-08  5:31   ` John Fastabend
2020-12-08  9:59     ` Brendan Jackman
2020-12-07 16:07 ` [PATCH bpf-next v4 07/11] bpf: Add instructions for atomic_[cmp]xchg Brendan Jackman
2020-12-08  1:44   ` Yonghong Song
2020-12-08  6:37   ` John Fastabend
2020-12-14 15:39     ` Brendan Jackman
2020-12-08  6:42   ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 08/11] bpf: Pull out a macro for interpreting atomic ALU operations Brendan Jackman
2020-12-07 16:07 ` [PATCH bpf-next v4 09/11] bpf: Add bitwise atomic instructions Brendan Jackman
2020-12-08  1:47   ` Yonghong Song
2020-12-10  0:22   ` kernel test robot
2020-12-07 16:07 ` [PATCH bpf-next v4 10/11] bpf: Add tests for new BPF atomic operations Brendan Jackman
2020-12-08  3:18   ` Yonghong Song
2020-12-08 12:41     ` Brendan Jackman
2020-12-08 16:38       ` Yonghong Song
2020-12-08 16:59         ` Brendan Jackman
2020-12-08 18:15           ` Yonghong Song
2020-12-15 11:12             ` Brendan Jackman
2020-12-16  7:18               ` Yonghong Song
2020-12-16 11:51                 ` Brendan Jackman
2020-12-16 20:00                   ` Yonghong Song
2020-12-07 16:07 ` [PATCH bpf-next v4 11/11] bpf: Document new atomic instructions Brendan Jackman
2020-12-08  3:25   ` Yonghong Song

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