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Subject: Re: [PATCH bpf-next] s390/bpf: make sure JIT passes do not increase
 code size
To:     Ilya Leoshkevich <iii@linux.ibm.com>,
        Alexei Starovoitov <ast@kernel.org>
Cc:     bpf@vger.kernel.org, Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>
References: <20191114151820.53222-1-iii@linux.ibm.com>
From:   Daniel Borkmann <daniel@iogearbox.net>
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Date:   Fri, 15 Nov 2019 23:28:12 +0100
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On 11/14/19 4:18 PM, Ilya Leoshkevich wrote:
> The upcoming s390 branch length extension patches rely on "passes do
> not increase code size" property in order to consistently choose between
> short and long branches. Currently this property does not hold between
> the first and the second passes for register save/restore sequences, as
> well as various code fragments that depend on SEEN_* flags.
> 
> Generate the code during the first pass conservatively: assume register
> save/restore sequences have the maximum possible length, and that all
> SEEN_* flags are set.
> 
> Also refuse to JIT if this happens anyway (e.g. due to a bug), as this
> might lead to verifier bypass once long branches are introduced.
> 
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>

Applied, thanks!