Re: [PATCH v2] arm: eBPF JIT compiler

From: Shubham Bansal <illusionist.neo@gmail.com>
To: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Kees Cook <keescook@chromium.org>,
	Network Development <netdev@vger.kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Alexei Starovoitov <ast@kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	LKML <linux-kernel@vger.kernel.org>, Andrew Lunn <andrew@lunn.ch>
Subject: Re: [PATCH v2] arm: eBPF JIT compiler
Date: Mon, 12 Jun 2017 21:11:58 +0530	[thread overview]
Message-ID: <CAHgaXdKqpgKzPHCbeagy_AArrir48UinLWX3yKxcvMkQ4_7apQ@mail.gmail.com> (raw)
In-Reply-To: <20170612110611.GC4902@n2100.armlinux.org.uk>

Hi Russel,

On Mon, Jun 12, 2017 at 4:36 PM, Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
> 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@gmail.com> 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.

Done. Thanks :)
Please check if you can find anymore issues with the code. I really
appreciate it.

-Shubham