Re: [PATCH v2] arm: eBPF JIT compiler

[Russell King - ARM Linux]

On Mon, Jun 12, 2017 at 12:21:03PM +0200, Daniel Borkmann wrote:
> On 05/30/2017 09:19 PM, Kees Cook wrote:
> >On Thu, May 25, 2017 at 4:13 PM, Shubham Bansal
> ><illusionist.neo@xxxxxxxxx> wrote:
> >>+static int validate_code(struct jit_ctx *ctx)
> >>+{
> >>+       int i;
> >>+
> >>+       for (i = 0; i < ctx->idx; i++) {
> >>+               u32 a32_insn = le32_to_cpu(ctx->target[i]);
> 
> Given __opcode_to_mem_arm(ARM_INST_UDF) is used to fill the image,
> perhaps use the __mem_to_opcode_arm() helper for the check?
> 
> >>+               if (a32_insn == ARM_INST_UDF)

The following is probably better:

		if (ctx->target[i] == __opcode_to_mem_arm(ARM_INST_UDF))

since then you can take advantage of the compiler optimising the
constant rather than having to do a byte swap on an unknown 32-bit
value.

-- 
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