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: 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 0a8b3d0903c472a42f14ab596fd53b2ab99487c6..f0cad9692952e099bb84a8eccd17c77db3c86345 100644 (file)
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -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);