From: Jiri Olsa <jolsa@redhat.com>
To: Yonghong Song <yhs@fb.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andriin@fb.com>,
"Steven Rostedt (VMware)" <rostedt@goodmis.org>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>, Daniel Xu <dxu@dxuuu.xyz>,
Viktor Malik <vmalik@redhat.com>
Subject: Re: [PATCH 11/19] bpf: Add support to load multi func tracing program
Date: Mon, 7 Jun 2021 20:18:48 +0200 [thread overview]
Message-ID: <YL5jCPZhmMxfFy26@krava> (raw)
In-Reply-To: <db5c591c-c5f2-9bcc-28bf-f5890c2cf61c@fb.com>
On Sun, Jun 06, 2021 at 08:56:47PM -0700, Yonghong Song wrote:
>
>
> On 6/5/21 4:10 AM, Jiri Olsa wrote:
> > Adding support to load tracing program with new BPF_F_MULTI_FUNC flag,
> > that allows the program to be loaded without specific function to be
> > attached to.
> >
> > The verifier assumes the program is using all (6) available arguments
>
> Is this a verifier failure or it is due to the check in the
> beginning of function arch_prepare_bpf_trampoline()?
>
> /* x86-64 supports up to 6 arguments. 7+ can be added in the future
> */
> if (nr_args > 6)
> return -ENOTSUPP;
yes, that's the limit.. it allows the traced program to
touch 6 arguments, because it's the maximum for JIT
>
> If it is indeed due to arch_prepare_bpf_trampoline() maybe we
> can improve it instead of specially processing the first argument
> "ip" in quite some places?
do you mean to teach JIT to process more than 6 arguments?
>
> > as unsigned long values. We can't add extra ip argument at this time,
> > because JIT on x86 would fail to process this function. Instead we
> > allow to access extra first 'ip' argument in btf_ctx_access.
> >
> > Such program will be allowed to be attached to multiple functions
> > in following patches.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> > include/linux/bpf.h | 1 +
> > include/uapi/linux/bpf.h | 7 +++++++
> > kernel/bpf/btf.c | 5 +++++
> > kernel/bpf/syscall.c | 35 +++++++++++++++++++++++++++++-----
> > kernel/bpf/verifier.c | 3 ++-
> > tools/include/uapi/linux/bpf.h | 7 +++++++
> > 6 files changed, 52 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 6cbf3c81c650..23221e0e8d3c 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -845,6 +845,7 @@ struct bpf_prog_aux {
> > bool sleepable;
> > bool tail_call_reachable;
> > struct hlist_node tramp_hlist;
> > + bool multi_func;
>
> Move this field right after "tail_call_reachable"?
>
> > /* BTF_KIND_FUNC_PROTO for valid attach_btf_id */
> > const struct btf_type *attach_func_proto;
> > /* function name for valid attach_btf_id */
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 2c1ba70abbf1..ad9340fb14d4 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -1109,6 +1109,13 @@ enum bpf_link_type {
> > */
> > #define BPF_F_SLEEPABLE (1U << 4)
> > +/* If BPF_F_MULTI_FUNC is used in BPF_PROG_LOAD command, the verifier does
> > + * not expect BTF ID for the program, instead it assumes it's function
> > + * with 6 u64 arguments. No trampoline is created for the program. Such
> > + * program can be attached to multiple functions.
> > + */
> > +#define BPF_F_MULTI_FUNC (1U << 5)
> > +
> > /* When BPF ldimm64's insn[0].src_reg != 0 then this can have
> > * the following extensions:
> > *
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index a6e39c5ea0bf..c233aaa6a709 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -4679,6 +4679,11 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
> > args++;
> > nr_args--;
> > }
> > + if (prog->aux->multi_func) {
> > + if (arg == 0)
> > + return true;
> > + arg--;
>
> Some comments in the above to mention like "the first 'ip' argument
> is omitted" will be good.
will do, thanks
jirka
>
> > + }
> > if (arg > nr_args) {
> > bpf_log(log, "func '%s' doesn't have %d-th argument\n",
> [...]
>
next prev parent reply other threads:[~2021-06-07 18:19 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-05 11:10 [RFCv3 00/19] x86/ftrace/bpf: Add batch support for direct/tracing attach Jiri Olsa
2021-06-05 11:10 ` [PATCH 01/19] x86/ftrace: Remove extra orig rax move Jiri Olsa
2021-06-05 11:10 ` [PATCH 02/19] x86/ftrace: Remove fault protection code in prepare_ftrace_return Jiri Olsa
2021-06-05 11:10 ` [PATCH 03/19] x86/ftrace: Make function graph use ftrace directly Jiri Olsa
2021-06-08 18:35 ` Andrii Nakryiko
2021-06-08 18:51 ` Jiri Olsa
2021-06-08 19:11 ` Steven Rostedt
2021-06-05 11:10 ` [PATCH 04/19] tracing: Add trampoline/graph selftest Jiri Olsa
2021-06-05 11:10 ` [PATCH 05/19] ftrace: Add ftrace_add_rec_direct function Jiri Olsa
2021-06-05 11:10 ` [PATCH 06/19] ftrace: Add multi direct register/unregister interface Jiri Olsa
2021-06-05 11:10 ` [PATCH 07/19] ftrace: Add multi direct modify interface Jiri Olsa
2021-06-05 11:10 ` [PATCH 08/19] ftrace/samples: Add multi direct interface test module Jiri Olsa
2021-06-05 11:10 ` [PATCH 09/19] bpf, x64: Allow to use caller address from stack Jiri Olsa
2021-06-07 3:07 ` Yonghong Song
2021-06-07 18:13 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 10/19] bpf: Allow to store caller's ip as argument Jiri Olsa
2021-06-07 3:21 ` Yonghong Song
2021-06-07 18:15 ` Jiri Olsa
2021-06-08 18:49 ` Andrii Nakryiko
2021-06-08 20:58 ` Jiri Olsa
2021-06-08 21:02 ` Andrii Nakryiko
2021-06-08 21:11 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 11/19] bpf: Add support to load multi func tracing program Jiri Olsa
2021-06-07 3:56 ` Yonghong Song
2021-06-07 18:18 ` Jiri Olsa [this message]
2021-06-07 19:35 ` Yonghong Song
2021-06-05 11:10 ` [PATCH 12/19] bpf: Add bpf_trampoline_alloc function Jiri Olsa
2021-06-05 11:10 ` [PATCH 13/19] bpf: Add support to link multi func tracing program Jiri Olsa
2021-06-07 5:36 ` Yonghong Song
2021-06-07 18:25 ` Jiri Olsa
2021-06-07 19:39 ` Yonghong Song
2021-06-08 15:42 ` Alexei Starovoitov
2021-06-08 18:17 ` Jiri Olsa
2021-06-08 18:49 ` Alexei Starovoitov
2021-06-08 21:07 ` Jiri Olsa
2021-06-08 23:05 ` Alexei Starovoitov
2021-06-09 5:08 ` Andrii Nakryiko
2021-06-09 13:42 ` Jiri Olsa
2021-06-09 13:33 ` Jiri Olsa
2021-06-09 5:18 ` Andrii Nakryiko
2021-06-09 13:53 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 14/19] libbpf: Add btf__find_by_pattern_kind function Jiri Olsa
2021-06-09 5:29 ` Andrii Nakryiko
2021-06-09 13:59 ` Jiri Olsa
2021-06-09 14:19 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 15/19] libbpf: Add support to link multi func tracing program Jiri Olsa
2021-06-07 5:49 ` Yonghong Song
2021-06-07 18:28 ` Jiri Olsa
2021-06-07 19:42 ` Yonghong Song
2021-06-07 20:11 ` Jiri Olsa
2021-06-09 5:34 ` Andrii Nakryiko
2021-06-09 14:17 ` Jiri Olsa
2021-06-10 17:05 ` Andrii Nakryiko
2021-06-10 20:35 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 16/19] selftests/bpf: Add fentry multi func test Jiri Olsa
2021-06-07 6:06 ` Yonghong Song
2021-06-07 18:42 ` Jiri Olsa
2021-06-09 5:40 ` Andrii Nakryiko
2021-06-09 14:29 ` Jiri Olsa
2021-06-10 17:00 ` Andrii Nakryiko
2021-06-10 20:28 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 17/19] selftests/bpf: Add fexit " Jiri Olsa
2021-06-05 11:10 ` [PATCH 18/19] selftests/bpf: Add fentry/fexit " Jiri Olsa
2021-06-09 5:41 ` Andrii Nakryiko
2021-06-09 14:29 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 19/19] selftests/bpf: Temporary fix for fentry_fexit_multi_test Jiri Olsa
2021-06-17 20:29 ` [RFCv3 00/19] x86/ftrace/bpf: Add batch support for direct/tracing attach Andrii Nakryiko
2021-06-19 8:33 ` Jiri Olsa
2021-06-19 16:19 ` Yonghong Song
2021-06-19 17:09 ` Jiri Olsa
2021-06-20 16:56 ` Yonghong Song
2021-06-20 17:47 ` Alexei Starovoitov
2021-06-21 6:46 ` Andrii Nakryiko
2021-06-21 6:50 ` Andrii Nakryiko
2021-07-06 20:26 ` Andrii Nakryiko
2021-07-07 15:19 ` Jiri Olsa
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