Commit 74007cfc authored by Brendan Jackman's avatar Brendan Jackman Committed by Alexei Starovoitov
Browse files

bpf: x86: Factor out emission of REX byte 



The JIT case for encoding atomic ops is about to get more
complicated. In order to make the review & resulting code easier,
let's factor out some shared helpers.

Signed-off-by: default avatarBrendan Jackman <jackmanb@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-3-jackmanb@google.com
parent 11c11d07

arch/x86/net/bpf_jit_comp.c

+23 −16
Original line number Diff line number Diff line
@@ -702,6 +702,21 @@ static void emit_insn_suffix(u8 **pprog, u32 ptr_reg, u32 val_reg, int off) 
	*pprog = prog;

}



/*

 * Emit a REX byte if it will be necessary to address these registers

 */

static void maybe_emit_mod(u8 **pprog, u32 dst_reg, u32 src_reg, bool is64)

{

	u8 *prog = *pprog;

	int cnt = 0;



	if (is64)

		EMIT1(add_2mod(0x48, dst_reg, src_reg));

	else if (is_ereg(dst_reg) || is_ereg(src_reg))

		EMIT1(add_2mod(0x40, dst_reg, src_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)

{
@@ -854,10 +869,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, 
			case BPF_OR: b2 = 0x09; break;

			case BPF_XOR: b2 = 0x31; break;

			}

			if (BPF_CLASS(insn->code) == BPF_ALU64)

				EMIT1(add_2mod(0x48, dst_reg, src_reg));

			else if (is_ereg(dst_reg) || is_ereg(src_reg))

				EMIT1(add_2mod(0x40, dst_reg, src_reg));

			maybe_emit_mod(&prog, dst_reg, src_reg,

				       BPF_CLASS(insn->code) == BPF_ALU64);

			EMIT2(b2, add_2reg(0xC0, dst_reg, src_reg));

			break;
@@ -1302,20 +1315,16 @@ st: if (is_imm8(insn->off)) 
		case BPF_JMP32 | BPF_JSGE | BPF_X:

		case BPF_JMP32 | BPF_JSLE | BPF_X:

			/* cmp dst_reg, src_reg */

			if (BPF_CLASS(insn->code) == BPF_JMP)

				EMIT1(add_2mod(0x48, dst_reg, src_reg));

			else if (is_ereg(dst_reg) || is_ereg(src_reg))

				EMIT1(add_2mod(0x40, dst_reg, src_reg));

			maybe_emit_mod(&prog, dst_reg, src_reg,

				       BPF_CLASS(insn->code) == BPF_JMP);

			EMIT2(0x39, add_2reg(0xC0, dst_reg, src_reg));

			goto emit_cond_jmp;



		case BPF_JMP | BPF_JSET | BPF_X:

		case BPF_JMP32 | BPF_JSET | BPF_X:

			/* test dst_reg, src_reg */

			if (BPF_CLASS(insn->code) == BPF_JMP)

				EMIT1(add_2mod(0x48, dst_reg, src_reg));

			else if (is_ereg(dst_reg) || is_ereg(src_reg))

				EMIT1(add_2mod(0x40, dst_reg, src_reg));

			maybe_emit_mod(&prog, dst_reg, src_reg,

				       BPF_CLASS(insn->code) == BPF_JMP);

			EMIT2(0x85, add_2reg(0xC0, dst_reg, src_reg));

			goto emit_cond_jmp;
@@ -1351,10 +1360,8 @@ st: if (is_imm8(insn->off)) 
		case BPF_JMP32 | BPF_JSLE | BPF_K:

			/* test dst_reg, dst_reg to save one extra byte */

			if (imm32 == 0) {

				if (BPF_CLASS(insn->code) == BPF_JMP)

					EMIT1(add_2mod(0x48, dst_reg, dst_reg));

				else if (is_ereg(dst_reg))

					EMIT1(add_2mod(0x40, dst_reg, dst_reg));

				maybe_emit_mod(&prog, dst_reg, dst_reg,

					       BPF_CLASS(insn->code) == BPF_JMP);

				EMIT2(0x85, add_2reg(0xC0, dst_reg, dst_reg));

				goto emit_cond_jmp;

			}