[PATCH 5.15 157/177] bpf, x64: Factor out emission of REX byte in more cases

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Jie Meng <jmeng@xxxxxx>

commit 6364d7d75a0e015a405d1f8a07f267f076c36ca6 upstream.

Introduce a single reg version of maybe_emit_mod() and factor out
common code in more cases.

Signed-off-by: Jie Meng <jmeng@xxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
Link: https://lore.kernel.org/bpf/20211006194135.608932-1-jmeng@xxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/net/bpf_jit_comp.c |   50 ++++++++++++++++++++++----------------------
 1 file changed, 26 insertions(+), 24 deletions(-)

--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -721,6 +721,20 @@ static void maybe_emit_mod(u8 **pprog, u
 	*pprog = prog;
 }
 
+/*
+ * Similar version of maybe_emit_mod() for a single register
+ */
+static void maybe_emit_1mod(u8 **pprog, u32 reg, bool is64)
+{
+	u8 *prog = *pprog;
+
+	if (is64)
+		EMIT1(add_1mod(0x48, reg));
+	else if (is_ereg(reg))
+		EMIT1(add_1mod(0x40, reg));
+	*pprog = prog;
+}
+
 /* LDX: dst_reg = *(u8*)(src_reg + off) */
 static void emit_ldx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
 {
@@ -951,10 +965,8 @@ static int do_jit(struct bpf_prog *bpf_p
 			/* neg dst */
 		case BPF_ALU | BPF_NEG:
 		case BPF_ALU64 | BPF_NEG:
-			if (BPF_CLASS(insn->code) == BPF_ALU64)
-				EMIT1(add_1mod(0x48, dst_reg));
-			else if (is_ereg(dst_reg))
-				EMIT1(add_1mod(0x40, dst_reg));
+			maybe_emit_1mod(&prog, dst_reg,
+					BPF_CLASS(insn->code) == BPF_ALU64);
 			EMIT2(0xF7, add_1reg(0xD8, dst_reg));
 			break;
 
@@ -968,10 +980,8 @@ static int do_jit(struct bpf_prog *bpf_p
 		case BPF_ALU64 | BPF_AND | BPF_K:
 		case BPF_ALU64 | BPF_OR | BPF_K:
 		case BPF_ALU64 | BPF_XOR | BPF_K:
-			if (BPF_CLASS(insn->code) == BPF_ALU64)
-				EMIT1(add_1mod(0x48, dst_reg));
-			else if (is_ereg(dst_reg))
-				EMIT1(add_1mod(0x40, dst_reg));
+			maybe_emit_1mod(&prog, dst_reg,
+					BPF_CLASS(insn->code) == BPF_ALU64);
 
 			/*
 			 * b3 holds 'normal' opcode, b2 short form only valid
@@ -1112,10 +1122,8 @@ static int do_jit(struct bpf_prog *bpf_p
 		case BPF_ALU64 | BPF_LSH | BPF_K:
 		case BPF_ALU64 | BPF_RSH | BPF_K:
 		case BPF_ALU64 | BPF_ARSH | BPF_K:
-			if (BPF_CLASS(insn->code) == BPF_ALU64)
-				EMIT1(add_1mod(0x48, dst_reg));
-			else if (is_ereg(dst_reg))
-				EMIT1(add_1mod(0x40, dst_reg));
+			maybe_emit_1mod(&prog, dst_reg,
+					BPF_CLASS(insn->code) == BPF_ALU64);
 
 			b3 = simple_alu_opcodes[BPF_OP(insn->code)];
 			if (imm32 == 1)
@@ -1146,10 +1154,8 @@ static int do_jit(struct bpf_prog *bpf_p
 			}
 
 			/* shl %rax, %cl | shr %rax, %cl | sar %rax, %cl */
-			if (BPF_CLASS(insn->code) == BPF_ALU64)
-				EMIT1(add_1mod(0x48, dst_reg));
-			else if (is_ereg(dst_reg))
-				EMIT1(add_1mod(0x40, dst_reg));
+			maybe_emit_1mod(&prog, dst_reg,
+					BPF_CLASS(insn->code) == BPF_ALU64);
 
 			b3 = simple_alu_opcodes[BPF_OP(insn->code)];
 			EMIT2(0xD3, add_1reg(b3, dst_reg));
@@ -1459,10 +1465,8 @@ st:			if (is_imm8(insn->off))
 		case BPF_JMP | BPF_JSET | BPF_K:
 		case BPF_JMP32 | BPF_JSET | BPF_K:
 			/* test dst_reg, imm32 */
-			if (BPF_CLASS(insn->code) == BPF_JMP)
-				EMIT1(add_1mod(0x48, dst_reg));
-			else if (is_ereg(dst_reg))
-				EMIT1(add_1mod(0x40, dst_reg));
+			maybe_emit_1mod(&prog, dst_reg,
+					BPF_CLASS(insn->code) == BPF_JMP);
 			EMIT2_off32(0xF7, add_1reg(0xC0, dst_reg), imm32);
 			goto emit_cond_jmp;
 
@@ -1495,10 +1499,8 @@ st:			if (is_imm8(insn->off))
 			}
 
 			/* cmp dst_reg, imm8/32 */
-			if (BPF_CLASS(insn->code) == BPF_JMP)
-				EMIT1(add_1mod(0x48, dst_reg));
-			else if (is_ereg(dst_reg))
-				EMIT1(add_1mod(0x40, dst_reg));
+			maybe_emit_1mod(&prog, dst_reg,
+					BPF_CLASS(insn->code) == BPF_JMP);
 
 			if (is_imm8(imm32))
 				EMIT3(0x83, add_1reg(0xF8, dst_reg), imm32);