bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jakub Kicinski <jakub.kicinski@netronome.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: 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: [PATCH bpf-next v2 1/5] bpf: Support injecting chain calls into BPF programs on load
Date: Sat, 5 Oct 2019 20:39:45 -0700	[thread overview]
Message-ID: <20191005203945.6b3845a9@cakuba.netronome.com> (raw)
In-Reply-To: <87d0fbo58l.fsf@toke.dk>

On Sat, 05 Oct 2019 12:29:14 +0200, Toke Høiland-Jørgensen wrote:
> >> +static int bpf_inject_chain_calls(struct bpf_verifier_env *env)
> >> +{
> >> +	struct bpf_prog *prog = env->prog;
> >> +	struct bpf_insn *insn = prog->insnsi;
> >> +	int i, cnt, delta = 0, ret = -ENOMEM;
> >> +	const int insn_cnt = prog->len;
> >> +	struct bpf_array *prog_array;
> >> +	struct bpf_prog *new_prog;
> >> +	size_t array_size;
> >> +
> >> +	struct bpf_insn call_next[] = {
> >> +		BPF_LD_IMM64(BPF_REG_2, 0),
> >> +		/* Save real return value for later */
> >> +		BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
> >> +		/* First try tail call with index ret+1 */
> >> +		BPF_MOV64_REG(BPF_REG_3, BPF_REG_0),  
> >
> > Don't we need to check against the max here, and spectre-proofing
> > here?  
> 
> No, I don't think so. This is just setting up the arguments for the
> BPF_TAIL_CALL instruction below. The JIT will do its thing with that and
> emit the range check and the retpoline stuff...

Sorry, wrong CPU bug, I meant Meltdown :)

https://elixir.bootlin.com/linux/v5.4-rc1/source/kernel/bpf/verifier.c#L9029

> >> +		BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 1),
> >> +		BPF_RAW_INSN(BPF_JMP | BPF_TAIL_CALL, 0, 0, 0, 0),
> >> +		/* If that doesn't work, try with index 0 (wildcard) */
> >> +		BPF_MOV64_IMM(BPF_REG_3, 0),
> >> +		BPF_RAW_INSN(BPF_JMP | BPF_TAIL_CALL, 0, 0, 0, 0),
> >> +		/* Restore saved return value and exit */
> >> +		BPF_MOV64_REG(BPF_REG_0, BPF_REG_6),
> >> +		BPF_EXIT_INSN()
> >> +	};  

  reply	other threads:[~2019-10-06  3:39 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-04 17:22 [PATCH bpf-next v2 0/5] xdp: Support multiple programs on a single interface through chain calls Toke Høiland-Jørgensen
2019-10-04 17:22 ` [PATCH bpf-next v2 1/5] bpf: Support injecting chain calls into BPF programs on load Toke Høiland-Jørgensen
2019-10-04 20:51   ` kbuild test robot
2019-10-04 21:12   ` kbuild test robot
2019-10-04 23:17   ` Jakub Kicinski
2019-10-05 10:29     ` Toke Høiland-Jørgensen
2019-10-06  3:39       ` Jakub Kicinski [this message]
2019-10-06 15:52         ` Toke Høiland-Jørgensen
2019-10-05 10:32     ` Toke Høiland-Jørgensen
2019-10-07  0:27   ` Alexei Starovoitov
2019-10-07 10:11     ` Toke Høiland-Jørgensen
2019-10-07 20:22       ` Daniel Borkmann
2019-10-08  9:00         ` Toke Høiland-Jørgensen
2019-10-07 20:45       ` Alexei Starovoitov
2019-10-08  9:02         ` Toke Høiland-Jørgensen
2019-10-04 17:22 ` [PATCH bpf-next v2 2/5] bpf: Add support for setting chain call sequence for programs Toke Høiland-Jørgensen
2019-10-04 23:18   ` Jakub Kicinski
2019-10-05 10:30     ` Toke Høiland-Jørgensen
2019-10-04 17:22 ` [PATCH bpf-next v2 3/5] tools: Update bpf.h header for program chain calls Toke Høiland-Jørgensen
2019-10-04 17:22 ` [PATCH bpf-next v2 4/5] libbpf: Add syscall wrappers for BPF_PROG_CHAIN_* commands Toke Høiland-Jørgensen
2019-10-04 17:22 ` [PATCH bpf-next v2 5/5] selftests: Add tests for XDP chain calls Toke Høiland-Jørgensen

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191005203945.6b3845a9@cakuba.netronome.com \
    --to=jakub.kicinski@netronome.com \
    --cc=alan.maguire@oracle.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=brouer@redhat.com \
    --cc=daniel@iogearbox.net \
    --cc=davem@davemloft.net \
    --cc=kafai@fb.com \
    --cc=lmb@cloudflare.com \
    --cc=marek@cloudflare.com \
    --cc=netdev@vger.kernel.org \
    --cc=songliubraving@fb.com \
    --cc=toke@redhat.com \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).