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Commit f9ff5018 authored by Russell King's avatar Russell King Committed by Daniel Borkmann
Browse files

ARM: net: bpf: improve 64-bit load immediate implementation 



Rather than writing each 32-bit half of the 64-bit immediate value
separately when the register is on the stack:

  movw    r6, #45056      ; 0xb000
  movt    r6, #60979      ; 0xee33
  str     r6, [fp, #-44]  ; 0xffffffd4
  mov     r6, #0
  str     r6, [fp, #-40]  ; 0xffffffd8

arrange to use the double-word store when available instead:

  movw    r6, #45056      ; 0xb000
  movt    r6, #60979      ; 0xee33
  mov     r7, #0
  strd    r6, [fp, #-44]  ; 0xffffffd4

Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 6fd06660

arch/arm/net/bpf_jit_32.c

+20 −12
Original line number Diff line number Diff line
@@ -599,8 +599,19 @@ static inline void emit_a32_mov_i(const s8 dst, const u32 val, 
	}

}



static void emit_a32_mov_i64(const s8 dst[], u64 val, struct jit_ctx *ctx)

{

	const s8 *tmp = bpf2a32[TMP_REG_1];

	const s8 *rd = is_stacked(dst_lo) ? tmp : dst;



	emit_mov_i(rd[1], (u32)val, ctx);

	emit_mov_i(rd[0], val >> 32, ctx);



	arm_bpf_put_reg64(dst, rd, ctx);

}



/* Sign extended move */

static inline void emit_a32_mov_i64(const bool is64, const s8 dst[],

static inline void emit_a32_mov_se_i64(const bool is64, const s8 dst[],

				       const u32 val, struct jit_ctx *ctx) {

	u32 hi = 0;
@@ -1309,7 +1320,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) 
			break;

		case BPF_K:

			/* Sign-extend immediate value to destination reg */

			emit_a32_mov_i64(is64, dst, imm, ctx);

			emit_a32_mov_se_i64(is64, dst, imm, ctx);

			break;

		}

		break;
@@ -1358,7 +1369,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) 
			 * value into temporary reg and then it would be

			 * safe to do the operation on it.

			 */

			emit_a32_mov_i64(is64, tmp2, imm, ctx);

			emit_a32_mov_se_i64(is64, tmp2, imm, ctx);

			emit_a32_alu_r64(is64, dst, tmp2, ctx, BPF_OP(code));

			break;

		}
@@ -1454,7 +1465,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) 
			 * reg then it would be safe to do the operation

			 * on it.

			 */

			emit_a32_mov_i64(is64, tmp2, imm, ctx);

			emit_a32_mov_se_i64(is64, tmp2, imm, ctx);

			emit_a32_mul_r64(dst, tmp2, ctx);

			break;

		}
@@ -1506,12 +1517,9 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) 
	/* dst = imm64 */

	case BPF_LD | BPF_IMM | BPF_DW:

	{

		const struct bpf_insn insn1 = insn[1];

		u32 hi, lo = imm;

		u64 val = (u32)imm | (u64)insn[1].imm << 32;



		hi = insn1.imm;

		emit_a32_mov_i(dst_lo, lo, ctx);

		emit_a32_mov_i(dst_hi, hi, ctx);

		emit_a32_mov_i64(dst, val, ctx);



		return 1;

	}
@@ -1531,7 +1539,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) 
		switch (BPF_SIZE(code)) {

		case BPF_DW:

			/* Sign-extend immediate value into temp reg */

			emit_a32_mov_i64(true, tmp2, imm, ctx);

			emit_a32_mov_se_i64(true, tmp2, imm, ctx);

			emit_str_r(dst_lo, tmp2[1], off, ctx, BPF_W);

			emit_str_r(dst_lo, tmp2[0], off+4, ctx, BPF_W);

			break;
@@ -1620,7 +1628,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) 
		rm = tmp2[0];

		rn = tmp2[1];

		/* Sign-extend immediate value */

		emit_a32_mov_i64(true, tmp2, imm, ctx);

		emit_a32_mov_se_i64(true, tmp2, imm, ctx);

go_jmp:

		/* Setup destination register */

		rd = arm_bpf_get_reg64(dst, tmp, ctx);