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

Russell King (Oracle)
2023-09-07T16:46:38Z

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.

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