Commit b5045229 authored by Russell King's avatar Russell King Committed by Daniel Borkmann
Browse files

ARM: net: bpf: avoid reloading 'array' 



Rearranging the order of the initial tail call code a little allows is
to avoid reloading the 'array' pointer.

Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent aaffd2f5

arch/arm/net/bpf_jit_32.c

+4 −5
Original line number Diff line number Diff line
@@ -1064,16 +1064,16 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx) 
	BUILD_BUG_ON(offsetof(struct bpf_array, map.max_entries) >

		     ARM_INST_LDST__IMM12);

	off = offsetof(struct bpf_array, map.max_entries);

	/* array->map.max_entries */

	r_array = arm_bpf_get_reg32(r2[1], tmp2[1], ctx);

	emit(ARM_LDR_I(tmp[1], r_array, off), ctx);

	r_array = arm_bpf_get_reg32(r2[1], tmp2[0], ctx);

	/* index is 32-bit for arrays */

	r_index = arm_bpf_get_reg32(r3[1], tmp2[1], ctx);

	/* array->map.max_entries */

	emit(ARM_LDR_I(tmp[1], r_array, off), ctx);

	/* index >= array->map.max_entries */

	emit(ARM_CMP_R(r_index, tmp[1]), ctx);

	_emit(ARM_COND_CS, ARM_B(jmp_offset), ctx);



	/* tmp2[1] = index */

	/* tmp2[0] = array, tmp2[1] = index */



	/* if (tail_call_cnt > MAX_TAIL_CALL_CNT)

	 *	goto out;
@@ -1095,7 +1095,6 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx) 
	 */

	BUILD_BUG_ON(imm8m(offsetof(struct bpf_array, ptrs)) < 0);

	off = imm8m(offsetof(struct bpf_array, ptrs));

	r_array = arm_bpf_get_reg32(r2[1], tmp2[0], ctx);

	emit(ARM_ADD_I(tmp[1], r_array, off), ctx);

	emit(ARM_LDR_R_SI(tmp[1], tmp[1], r_index, SRTYPE_ASL, 2), ctx);

	emit(ARM_CMP_I(tmp[1], 0), ctx);

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