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ARM: net: bpf: avoid reloading 'index' 

Avoid reloading 'index' after we have validated it - it remains in
tmp2[1] up to the point that we begin the code to index the pointer
array, so with a little rearrangement of the registers, we can use
the already loaded value.

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 10:32:22 +01:00 committed by Daniel Borkmann
parent 2b6958ef11
commit aaffd2f5c3
1 changed files with 3 additions and 2 deletions
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5
arch/arm/net/bpf_jit_32.c
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@ -1073,6 +1073,8 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
emit(ARM_CMP_R(r_index, tmp[1]), ctx);
_emit(ARM_COND_CS, ARM_B(jmp_offset), ctx);
/* tmp2[1] = index */
/* if (tail_call_cnt > MAX_TAIL_CALL_CNT)
* goto out;
* tail_call_cnt++;
@ -1093,9 +1095,8 @@ 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[1], ctx);
r_array = arm_bpf_get_reg32(r2[1], tmp2[0], ctx);
emit(ARM_ADD_I(tmp[1], r_array, off), ctx);
r_index = arm_bpf_get_reg32(r3[1], tmp2[1], ctx);
emit(ARM_LDR_R_SI(tmp[1], tmp[1], r_index, SRTYPE_ASL, 2), ctx);
emit(ARM_CMP_I(tmp[1], 0), ctx);
_emit(ARM_COND_EQ, ARM_B(jmp_offset), ctx);