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ARM: net: bpf: avoid reloading 'array'

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

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Russell King 2018-07-11 10:32:28 +01:00 committed by Daniel Borkmann
parent aaffd2f5c3
commit b504522998
1 changed files with 4 additions and 5 deletions
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9
arch/arm/net/bpf_jit_32.c
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@ -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);