From: Daniel Borkmann <daniel@iogearbox.net>
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>
Subject: Re: [PATCH bpf-next] s390/bpf: make sure JIT passes do not increase code size
Date: Fri, 15 Nov 2019 23:28:12 +0100 [thread overview]
Message-ID: <9486776a-a628-dfb4-9d41-726e251bf638@iogearbox.net> (raw)
In-Reply-To: <20191114151820.53222-1-iii@linux.ibm.com>
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!
prev parent reply other threads:[~2019-11-15 22:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-14 15:18 [PATCH bpf-next] s390/bpf: make sure JIT passes do not increase code size Ilya Leoshkevich
2019-11-15 22:28 ` Daniel Borkmann [this message]
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