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Commit 4c38e2f3 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Alexei Starovoitov
Browse files

bpf, x64: save few bytes when mul is in alu32 



Add a generic emit_mov_reg() helper in order to reuse it in BPF
multiplication to load the src into rax, we can save a few bytes
in alu32 while doing so.

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent d806a0cf

arch/x86/net/bpf_jit_comp.c

+28 −15
Original line number Diff line number Diff line
@@ -422,6 +422,24 @@ static void emit_mov_imm64(u8 **pprog, u32 dst_reg, 
	*pprog = prog;

}



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

{

	u8 *prog = *pprog;

	int cnt = 0;



	if (is64) {

		/* mov dst, src */

		EMIT_mov(dst_reg, src_reg);

	} else {

		/* mov32 dst, src */

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

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

		EMIT2(0x89, add_2reg(0xC0, dst_reg, src_reg));

	}



	*pprog = prog;

}



static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,

		  int oldproglen, struct jit_context *ctx)

{
@@ -480,16 +498,11 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, 
			EMIT2(b2, add_2reg(0xC0, dst_reg, src_reg));

			break;



			/* mov dst, src */

		case BPF_ALU64 | BPF_MOV | BPF_X:

			EMIT_mov(dst_reg, src_reg);

			break;



			/* mov32 dst, src */

		case BPF_ALU | BPF_MOV | BPF_X:

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

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

			EMIT2(0x89, add_2reg(0xC0, dst_reg, src_reg));

			emit_mov_reg(&prog,

				     BPF_CLASS(insn->code) == BPF_ALU64,

				     dst_reg, src_reg);

			break;



			/* neg dst */
@@ -615,6 +628,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, 
		case BPF_ALU | BPF_MUL | BPF_X:

		case BPF_ALU64 | BPF_MUL | BPF_K:

		case BPF_ALU64 | BPF_MUL | BPF_X:

		{

			bool is64 = BPF_CLASS(insn->code) == BPF_ALU64;



			if (dst_reg != BPF_REG_0)

				EMIT1(0x50); /* push rax */

			if (dst_reg != BPF_REG_3)
@@ -624,14 +640,11 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, 
			EMIT_mov(AUX_REG, dst_reg);



			if (BPF_SRC(insn->code) == BPF_X)

				/* mov rax, src_reg */

				EMIT_mov(BPF_REG_0, src_reg);

				emit_mov_reg(&prog, is64, BPF_REG_0, src_reg);

			else

				/* mov rax, imm32 */

				emit_mov_imm32(&prog, true,

					       BPF_REG_0, imm32);

				emit_mov_imm32(&prog, is64, BPF_REG_0, imm32);



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

			if (is64)

				EMIT1(add_1mod(0x48, AUX_REG));

			else if (is_ereg(AUX_REG))

				EMIT1(add_1mod(0x40, AUX_REG));
@@ -646,7 +659,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, 
				EMIT1(0x58); /* pop rax */

			}

			break;



		}

			/* shifts */

		case BPF_ALU | BPF_LSH | BPF_K:

		case BPF_ALU | BPF_RSH | BPF_K: