From: Edward Cree <ecree@solarflare.com>
To: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
"Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: John Fastabend <john.fastabend@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
Marek Majkowski <marek@cloudflare.com>,
Lorenz Bauer <lmb@cloudflare.com>,
Alan Maguire <alan.maguire@oracle.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
David Miller <davem@davemloft.net>, <netdev@vger.kernel.org>,
<bpf@vger.kernel.org>
Subject: Re: static and dynamic linking. Was: [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF
Date: Tue, 12 Nov 2019 21:25:06 +0000 [thread overview]
Message-ID: <8c251f3d-67bd-9bc2-8037-a15d93b48674@solarflare.com> (raw)
In-Reply-To: <20191112195223.cp5kcmkko54dsfbg@ast-mbp.dhcp.thefacebook.com>
On 12/11/2019 19:52, Alexei Starovoitov wrote:
> We haven't yet defined what 'extern' keyword in the program means.
> There are a preliminary patches for llvm to support extern variables. Extern
> functions are not done yet. We have to walk before we run. With dynamic linking
> I'm proposing an api for the kernel that I think will work regardless of how
> libbpf and llvm decide to define the meaning of 'extern'.
Fwiw the 'natural' C way of doing it would be that for any extern symbol in
the C file, the ELF file gets a symbol entry with st_shndx=SHN_UNDEF, and
code in .text that uses that symbol gets relocation entries. That's (AIUI)
how it works on 'normal' architectures, and that's what my ebld linker
understands; when it sees a definition in another file for that symbol
(matched just by the symbol name) it applies all the relocations of the
symbol to the appropriate progbits.
I don't really see what else you could define 'extern' to mean.
> Partial verification should be available regardless of
> whether kernel performs dynamic linking or libbpf staticly links multiple .o
> together.
It's not clear to me how partial verification would work for statically
linked programs — could you elaborate on this?
-Ed
next prev parent reply other threads:[~2019-11-12 21:25 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-07 17:20 [PATCH bpf-next v3 0/5] xdp: Support multiple programs on a single interface through chain calls Toke Høiland-Jørgensen
2019-10-07 17:20 ` [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF programs after each other Toke Høiland-Jørgensen
2019-10-07 20:42 ` Alexei Starovoitov
2019-10-08 8:07 ` Toke Høiland-Jørgensen
2019-10-09 1:51 ` Alexei Starovoitov
2019-10-09 8:03 ` Toke Høiland-Jørgensen
2019-10-10 4:41 ` Alexei Starovoitov
2019-10-14 12:35 ` Toke Høiland-Jørgensen
2019-10-14 17:08 ` John Fastabend
2019-10-14 18:48 ` Toke Høiland-Jørgensen
2019-10-15 16:30 ` Edward Cree
2019-10-15 16:42 ` Toke Høiland-Jørgensen
2019-10-15 18:33 ` Edward Cree
2019-10-17 12:11 ` Toke Høiland-Jørgensen
2019-10-22 17:27 ` Edward Cree
2019-10-22 18:07 ` Toke Høiland-Jørgensen
2019-11-12 2:51 ` static and dynamic linking. Was: [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF Alexei Starovoitov
2019-11-12 16:20 ` Toke Høiland-Jørgensen
2019-11-12 19:52 ` Alexei Starovoitov
2019-11-12 21:25 ` Edward Cree [this message]
2019-11-12 23:18 ` Alexei Starovoitov
2019-11-13 18:30 ` Edward Cree
2019-11-13 18:51 ` Andrii Nakryiko
2019-11-15 2:13 ` Alexei Starovoitov
2019-11-15 16:56 ` John Fastabend
2019-11-12 23:25 ` John Fastabend
2019-11-13 0:21 ` Alexei Starovoitov
2019-11-13 5:33 ` John Fastabend
2019-11-15 1:50 ` Alexei Starovoitov
2019-11-15 16:39 ` John Fastabend
2019-11-14 15:41 ` Toke Høiland-Jørgensen
2019-11-12 16:32 ` Edward Cree
2019-11-15 11:48 ` Lorenz Bauer
2019-11-15 23:02 ` Alexei Starovoitov
2019-11-18 13:29 ` Lorenz Bauer
2019-10-21 23:51 ` [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF programs after each other Edward Cree
2019-10-16 2:28 ` Alexei Starovoitov
2019-10-16 8:27 ` Jesper Dangaard Brouer
2019-10-16 10:35 ` Daniel Borkmann
2019-10-16 11:16 ` Toke Høiland-Jørgensen
2019-10-16 13:51 ` Toke Høiland-Jørgensen
2019-10-19 20:09 ` bpf indirect calls Alexei Starovoitov
2019-10-20 10:58 ` Toke Høiland-Jørgensen
2019-10-25 16:30 ` Alexei Starovoitov
2019-10-27 12:15 ` Toke Høiland-Jørgensen
2023-09-27 13:27 ` Matt Bobrowski
2023-09-29 21:06 ` Alexei Starovoitov
2023-10-02 18:50 ` Barret Rhoden
2023-10-06 9:36 ` Matt Bobrowski
2023-10-06 18:49 ` Alexei Starovoitov
2023-10-19 12:28 ` Matt Bobrowski
2019-10-09 10:19 ` [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF programs after each other Jesper Dangaard Brouer
2019-10-09 17:57 ` Alexei Starovoitov
2019-10-07 17:20 ` [PATCH bpf-next v3 2/5] bpf: Add support for setting chain call sequence for programs Toke Høiland-Jørgensen
2019-10-07 20:38 ` Daniel Borkmann
2019-10-08 8:09 ` Toke Høiland-Jørgensen
2019-10-07 17:20 ` [PATCH bpf-next v3 3/5] tools: Update bpf.h header for program chain calls Toke Høiland-Jørgensen
2019-10-07 17:20 ` [PATCH bpf-next v3 4/5] libbpf: Add syscall wrappers for BPF_PROG_CHAIN_* commands Toke Høiland-Jørgensen
2019-10-07 17:20 ` [PATCH bpf-next v3 5/5] selftests: Add tests for XDP chain calls Toke Høiland-Jørgensen
2019-10-07 18:58 ` [PATCH bpf-next v3 0/5] xdp: Support multiple programs on a single interface through " John Fastabend
2019-10-08 8:42 ` Toke Høiland-Jørgensen
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