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From: Jiri Olsa <jolsa@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andriin@fb.com>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
	Martin KaFai Lau <kafai@fb.com>, David Miller <davem@redhat.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Wenbo Zhang <ethercflow@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Brendan Gregg <bgregg@netflix.com>,
	Florent Revest <revest@chromium.org>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v9 bpf-next 10/14] bpf: Add d_path helper
Date: Wed, 5 Aug 2020 19:58:50 +0200
Message-ID: <20200805175850.GD319954@krava> (raw)
In-Reply-To: <CAEf4BzY5b8GhoovkKZgT4YSUUW=GPZBU0Qjg4eqeHNjoPHCMTw@mail.gmail.com>

On Tue, Aug 04, 2020 at 11:35:53PM -0700, Andrii Nakryiko wrote:
> On Sat, Aug 1, 2020 at 10:04 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding d_path helper function that returns full path for
> > given 'struct path' object, which needs to be the kernel
> > BTF 'path' object. The path is returned in buffer provided
> > 'buf' of size 'sz' and is zero terminated.
> >
> >   bpf_d_path(&file->f_path, buf, size);
> >
> > The helper calls directly d_path function, so there's only
> > limited set of function it can be called from. Adding just
> > very modest set for the start.
> >
> > Updating also bpf.h tools uapi header and adding 'path' to
> > bpf_helpers_doc.py script.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  include/uapi/linux/bpf.h       | 13 +++++++++
> >  kernel/trace/bpf_trace.c       | 48 ++++++++++++++++++++++++++++++++++
> >  scripts/bpf_helpers_doc.py     |  2 ++
> >  tools/include/uapi/linux/bpf.h | 13 +++++++++
> >  4 files changed, 76 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index eb5e0c38eb2c..a356ea1357bf 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -3389,6 +3389,18 @@ union bpf_attr {
> >   *             A non-negative value equal to or less than *size* on success,
> >   *             or a negative error in case of failure.
> >   *
> > + * int bpf_d_path(struct path *path, char *buf, u32 sz)
> 
> nit: probably would be good to do `const struct path *` here, even if
> we don't do const-ification properly in all helpers.

ok

> 
> > + *     Description
> > + *             Return full path for given 'struct path' object, which
> > + *             needs to be the kernel BTF 'path' object. The path is
> > + *             returned in buffer provided 'buf' of size 'sz' and
> 
> typo: in the provided buffer 'buf' of size ... ?

ugh, sure

> 
> > + *             is zero terminated.
> > + *
> > + *     Return
> > + *             On success, the strictly positive length of the string,
> > + *             including the trailing NUL character. On error, a negative
> > + *             value.
> > + *
> >   */
> >  #define __BPF_FUNC_MAPPER(FN)          \
> >         FN(unspec),                     \
> > @@ -3533,6 +3545,7 @@ union bpf_attr {
> >         FN(skc_to_tcp_request_sock),    \
> >         FN(skc_to_udp6_sock),           \
> >         FN(get_task_stack),             \
> > +       FN(d_path),                     \
> >         /* */
> >
> >  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index cb91ef902cc4..02a76e246545 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -1098,6 +1098,52 @@ static const struct bpf_func_proto bpf_send_signal_thread_proto = {
> >         .arg1_type      = ARG_ANYTHING,
> >  };
> >
> > +BPF_CALL_3(bpf_d_path, struct path *, path, char *, buf, u32, sz)
> > +{
> > +       int len;
> > +       char *p;
> > +
> > +       if (!sz)
> > +               return -ENAMETOOLONG;
> 
> if we are modeling this after bpf_probe_read_str(), sz == 0 returns
> success and just does nothing. I don't think anyone will ever handle
> or expect this error. I'd just return 0.

ook

thanks,
jirka


  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-01 17:03 [PATCH v9 bpf-next 00/14] " Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 01/14] tools resolve_btfids: Add size check to get_id function Jiri Olsa
2020-08-05  6:00   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 02/14] tools resolve_btfids: Add support for set symbols Jiri Olsa
2020-08-05  6:04   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 03/14] bpf: Move btf_resolve_size into __btf_resolve_size Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 04/14] bpf: Add elem_id pointer as argument to __btf_resolve_size Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 05/14] bpf: Add type_id " Jiri Olsa
2020-08-05  6:05   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 06/14] bpf: Remove recursion call in btf_struct_access Jiri Olsa
2020-08-05  6:12   ` Andrii Nakryiko
2020-08-05 17:36     ` Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 07/14] bpf: Factor btf_struct_access function Jiri Olsa
2020-08-05  6:18   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 08/14] bpf: Add btf_struct_ids_match function Jiri Olsa
2020-08-05  6:27   ` Andrii Nakryiko
2020-08-05 17:56     ` Jiri Olsa
2020-08-05 21:31       ` Jiri Olsa
2020-08-05 21:57         ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 09/14] bpf: Add BTF_SET_START/END macros Jiri Olsa
2020-08-05  6:29   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 10/14] bpf: Add d_path helper Jiri Olsa
2020-08-02  3:13   ` Alexei Starovoitov
2020-08-02 18:26     ` Jiri Olsa
2020-08-05  6:35   ` Andrii Nakryiko
2020-08-05 17:58     ` Jiri Olsa [this message]
2020-08-05 21:01       ` Jiri Olsa
2020-08-05 21:09         ` Andrii Nakryiko
2020-08-07  0:31   ` KP Singh
2020-08-07  8:35     ` Jiri Olsa
2020-08-07  9:42       ` KP Singh
2020-08-01 17:03 ` [PATCH v9 bpf-next 11/14] bpf: Update .BTF_ids section in btf.rst with sets info Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 12/14] selftests/bpf: Add verifier test for d_path helper Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 13/14] selftests/bpf: Add " Jiri Olsa
2020-08-05  6:40   ` Andrii Nakryiko
2020-08-05 18:00     ` Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 14/14] selftests/bpf: Add set test to resolve_btfids Jiri Olsa
2020-08-05  6:41   ` Andrii Nakryiko

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