From: Eduard Zingerman <eddyz87@gmail.com>
To: Daniel Xu <dxu@dxuuu.xyz>,
ndesaulniers@google.com, andrii@kernel.org, nathan@kernel.org,
daniel@iogearbox.net, ast@kernel.org,
steffen.klassert@secunet.com, antony.antony@secunet.com,
alexei.starovoitov@gmail.com, yonghong.song@linux.dev
Cc: martin.lau@linux.dev, song@kernel.org, john.fastabend@gmail.com,
kpsingh@kernel.org, sdf@google.com, haoluo@google.com,
jolsa@kernel.org, trix@redhat.com, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
devel@linux-ipsec.org, netdev@vger.kernel.org
Subject: Re: [PATCH ipsec-next v2 3/6] libbpf: Add BPF_CORE_WRITE_BITFIELD() macro
Date: Tue, 28 Nov 2023 19:59:01 +0200 [thread overview]
Message-ID: <20c593b6f31720a3d24d75e5e5cc3245b67249d1.camel@gmail.com> (raw)
In-Reply-To: <ed7920365daf5eff1c82892b57e918d3db786ac7.1701193577.git.dxu@dxuuu.xyz>
On Tue, 2023-11-28 at 10:54 -0700, Daniel Xu wrote:
> Similar to reading from CO-RE bitfields, we need a CO-RE aware bitfield
> writing wrapper to make the verifier happy.
>
> Two alternatives to this approach are:
>
> 1. Use the upcoming `preserve_static_offset` [0] attribute to disable
> CO-RE on specific structs.
> 2. Use broader byte-sized writes to write to bitfields.
>
> (1) is a bit a bit hard to use. It requires specific and
> not-very-obvious annotations to bpftool generated vmlinux.h. It's also
> not generally available in released LLVM versions yet.
>
> (2) makes the code quite hard to read and write. And especially if
> BPF_CORE_READ_BITFIELD() is already being used, it makes more sense to
> to have an inverse helper for writing.
>
> [0]: https://reviews.llvm.org/D133361
> From: Eduard Zingerman <eddyz87@gmail.com>
>
> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
> ---
Could you please also add a selftest (or several) using __retval()
annotation for this macro?
next prev parent reply other threads:[~2023-11-28 17:59 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-28 17:54 [PATCH ipsec-next v2 0/6] Add bpf_xdp_get_xfrm_state() kfunc Daniel Xu
2023-11-28 17:54 ` [PATCH ipsec-next v2 1/6] bpf: xfrm: " Daniel Xu
2023-11-28 17:54 ` [PATCH ipsec-next v2 2/6] bpf: xfrm: Add bpf_xdp_xfrm_state_release() kfunc Daniel Xu
2023-11-28 17:54 ` [PATCH ipsec-next v2 3/6] libbpf: Add BPF_CORE_WRITE_BITFIELD() macro Daniel Xu
2023-11-28 17:59 ` Eduard Zingerman [this message]
2023-11-28 19:15 ` Daniel Xu
2023-12-01 1:33 ` Daniel Xu
2023-12-01 16:13 ` Eduard Zingerman
2023-12-01 19:11 ` Andrii Nakryiko
2023-12-01 19:13 ` Andrii Nakryiko
2023-12-01 20:05 ` Daniel Xu
2023-11-28 17:54 ` [PATCH ipsec-next v2 4/6] bpf: selftests: test_tunnel: Use vmlinux.h declarations Daniel Xu
2023-11-28 17:54 ` [PATCH ipsec-next v2 5/6] bpf: selftests: Move xfrm tunnel test to test_progs Daniel Xu
2023-11-28 17:54 ` [PATCH ipsec-next v2 6/6] bpf: xfrm: Add selftest for bpf_xdp_get_xfrm_state() Daniel Xu
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