Re: [PATCH bpf-next v2 4/8] arm32, bpf: add support for unconditional bswap instruction

On Wed, Sep 06, 2023 at 06:33:16PM +0000, Puranjay Mohan wrote:

@@ -1633,8 +1633,10 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) /* dst = htobe(dst) */ case BPF_ALU | BPF_END | BPF_FROM_LE: case BPF_ALU | BPF_END | BPF_FROM_BE:

• /* dst = bswap(dst) */
• case BPF_ALU64 | BPF_END | BPF_TO_LE: rd = arm_bpf_get_reg64(dst, tmp, ctx);

• if (BPF_SRC(code) == BPF_FROM_LE)
  

• if (BPF_SRC(code) == BPF_FROM_LE && BPF_CLASS(code) != BPF_ALU64)
  

With the addition of the BPF_ALU64 case, I'm wondering why this if() is affected. If you were adding:

case BPF_ALU64 | BPF_END | BPF_FROM_LE:

then maybe there would be a reason, but the BPF_ALU64 | BPF_END | BPF_TO_LE case will never match even the original if() statement.