linux-kernel - Re: [PATCH] bpf: arm64: lift restriction on last instruction

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Message-ID: <CAMEtUuwJHC2eyOh3pD=qDXw1YbfJqx1a7W0o65n5Ur_B_TvNOA@mail.gmail.com>
Date:	Wed, 3 Dec 2014 07:54:32 -0800
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Zi Shen Lim <zlim.lnx@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Network Development <netdev@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bpf: arm64: lift restriction on last instruction

On Wed, Dec 3, 2014 at 12:38 AM, Zi Shen Lim <zlim.lnx@...il.com> wrote:
> Earlier implementation assumed last instruction is BPF_EXIT.
> Since this is no longer a restriction in eBPF, we remove this
> limitation.
>
> Per Alexei Starovoitov [1]:
>> classic BPF has a restriction that last insn is always BPF_RET.
>> eBPF doesn't have BPF_RET instruction and this restriction.
>> It has BPF_EXIT insn which can appear anywhere in the program
>> one or more times and it doesn't have to be last insn.
>
> [1] https://lkml.org/lkml/2014/11/27/2
>
> Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler")
> Signed-off-by: Zi Shen Lim <zlim.lnx@...il.com>

yours is cleaner than my own attempt to fix it.
Thanks!
Acked-by: Alexei Starovoitov <ast@...mgrid.com>
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