netdev - Re: [PATCH bpf-next 2/4] bpf: define bpf_jit_alloc_exec

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Message-ID: <20210929161804.GF22029@willie-the-truck>
Date:   Wed, 29 Sep 2021 17:18:04 +0100
From:   Will Deacon <will@...nel.org>
To:     Lorenz Bauer <lmb@...udflare.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Zi Shen Lim <zlim.lnx@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Andrii Nakryiko <andrii@...nel.org>,
        kernel-team@...udflare.com, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 2/4] bpf: define bpf_jit_alloc_exec_limit for
 arm64 JIT

On Fri, Sep 24, 2021 at 10:55:40AM +0100, Lorenz Bauer wrote:
> Expose the maximum amount of useable memory from the arm64 JIT.
> 
> Signed-off-by: Lorenz Bauer <lmb@...udflare.com>
> ---
>  arch/arm64/net/bpf_jit_comp.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index 41c23f474ea6..803e7773fa86 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -1136,6 +1136,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>  	return prog;
>  }
>  
> +u64 bpf_jit_alloc_exec_limit(void)
> +{
> +	return BPF_JIT_REGION_SIZE;
> +}

Looks like this won't result in a functional change, as we happen to return
SZ_128M anyway thanks to the way in which the modules area is constructed.

But making this explicit is definitely better, so:

Acked-by: Will Deacon <will@...nel.org>

(I'm assuming this will go via the bpf tree, but please shout if I should
take it via arm64 instead)

Will