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>

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index e22dc828420cf155779e5054ce2ad54754429a59..0a8b3d0903c472a42f14ab596fd53b2ab99487c6 100644 (file)
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -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);