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>,
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>, Andrii Nakryiko <andriin@fb.com>,
Brendan Gregg <bgregg@netflix.com>,
Florent Revest <revest@chromium.org>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v4 bpf-next 10/14] bpf: Add d_path helper
Date: Sun, 28 Jun 2020 21:42:42 +0200 [thread overview]
Message-ID: <20200628194242.GB2988321@krava> (raw)
In-Reply-To: <CAEf4BzY4EqkbB7Ob9EZAJrWdBRtH_k3sL=4JZzAiqkMXjYjNKA@mail.gmail.com>
On Fri, Jun 26, 2020 at 01:38:27PM -0700, Andrii Nakryiko wrote:
> On Thu, Jun 25, 2020 at 4:49 PM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding d_path helper function that returns full path
> > for give 'struct path' object, which needs to be the
> > kernel BTF 'path' object.
> >
> > The helper calls directly d_path function.
> >
> > 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 | 14 +++++++++-
> > kernel/trace/bpf_trace.c | 47 ++++++++++++++++++++++++++++++++++
> > scripts/bpf_helpers_doc.py | 2 ++
> > tools/include/uapi/linux/bpf.h | 14 +++++++++-
> > 4 files changed, 75 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 0cb8ec948816..23274c81f244 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -3285,6 +3285,17 @@ union bpf_attr {
> > * Dynamically cast a *sk* pointer to a *udp6_sock* pointer.
> > * Return
> > * *sk* if casting is valid, or NULL otherwise.
> > + *
> > + * int bpf_d_path(struct path *path, char *buf, u32 sz)
> > + * 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'.
> > + *
> > + * Return
> > + * length of returned string on success, or a negative
> > + * error in case of failure
>
> It's important to note whether string is always zero-terminated (I'm
> guessing it is, right?).
right, will add
>
> > + *
> > */
> > #define __BPF_FUNC_MAPPER(FN) \
> > FN(unspec), \
> > @@ -3427,7 +3438,8 @@ union bpf_attr {
> > FN(skc_to_tcp_sock), \
> > FN(skc_to_tcp_timewait_sock), \
> > FN(skc_to_tcp_request_sock), \
> > - FN(skc_to_udp6_sock),
> > + FN(skc_to_udp6_sock), \
> > + FN(d_path),
> >
> > /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> > * function eBPF program intends to call
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index b124d468688c..6f31e21565b6 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -1060,6 +1060,51 @@ 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)
> > +{
> > + char *p = d_path(path, buf, sz - 1);
> > + int len;
> > +
> > + if (IS_ERR(p)) {
> > + len = PTR_ERR(p);
> > + } else {
> > + len = strlen(p);
> > + if (len && p != buf) {
> > + memmove(buf, p, len);
> > + buf[len] = 0;
>
> if len above is zero, you won't zero-terminate it, so probably better
> to move buf[len] = 0 out of if to do unconditionally
good catch, will change
>
> > + }
> > + }
> > +
> > + return len;
> > +}
> > +
> > +BTF_SET_START(btf_whitelist_d_path)
> > +BTF_ID(func, vfs_truncate)
> > +BTF_ID(func, vfs_fallocate)
> > +BTF_ID(func, dentry_open)
> > +BTF_ID(func, vfs_getattr)
> > +BTF_ID(func, filp_close)
> > +BTF_SET_END(btf_whitelist_d_path)
> > +
> > +static bool bpf_d_path_allowed(const struct bpf_prog *prog)
> > +{
> > + return btf_id_set_contains(&btf_whitelist_d_path, prog->aux->attach_btf_id);
> > +}
> > +
>
> This looks pretty great and clean, considering what's happening under
> the covers. Nice work, thanks a lot!
>
> > +BTF_ID_LIST(bpf_d_path_btf_ids)
> > +BTF_ID(struct, path)
>
> this is a bit more confusing to read and error-prone, but I couldn't
> come up with any better way to do this... Still better than
> alternatives.
>
> > +
> > +static const struct bpf_func_proto bpf_d_path_proto = {
> > + .func = bpf_d_path,
> > + .gpl_only = true,
>
> Does it have to be GPL-only? What's the criteria? Sorry if this was
> brought up previously.
I don't think it's needed to be gpl_only, I'll set it to false
thanks,
jirka
next prev parent reply other threads:[~2020-06-28 19:42 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-25 22:12 [PATCH v4 bpf-next 00/14] bpf: Add d_path helper Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 01/14] bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object Jiri Olsa
2020-06-26 20:53 ` Andrii Nakryiko
2020-06-26 21:09 ` Yonghong Song
2020-06-28 19:09 ` Alexei Starovoitov
2020-06-28 19:35 ` Jiri Olsa
2020-06-28 20:53 ` Yonghong Song
2020-06-25 22:12 ` [PATCH v4 bpf-next 02/14] bpf: Compile resolve_btfids tool at kernel compilation start Jiri Olsa
2020-06-26 21:28 ` Andrii Nakryiko
2020-06-28 19:48 ` Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 03/14] bpf: Add BTF_ID_LIST/BTF_ID macros Jiri Olsa
2020-06-26 21:32 ` Andrii Nakryiko
2020-06-28 19:50 ` Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 04/14] bpf: Resolve BTF IDs in vmlinux image Jiri Olsa
2020-06-26 21:34 ` Andrii Nakryiko
2020-06-25 22:12 ` [PATCH v4 bpf-next 05/14] bpf: Remove btf_id helpers resolving Jiri Olsa
2020-06-26 21:36 ` Yonghong Song
2020-06-26 21:40 ` Andrii Nakryiko
2020-06-26 23:29 ` Yonghong Song
2020-06-28 18:50 ` Alexei Starovoitov
2020-06-28 20:00 ` Andrii Nakryiko
2020-06-28 20:16 ` Jiri Olsa
2020-06-28 20:59 ` Yonghong Song
2020-06-28 21:20 ` Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 06/14] bpf: Use BTF_ID to resolve bpf_ctx_convert struct Jiri Olsa
2020-06-26 21:44 ` Andrii Nakryiko
2020-06-26 21:44 ` Yonghong Song
2020-06-28 19:52 ` Jiri Olsa
2020-06-25 22:12 ` [PATCH v4 bpf-next 07/14] bpf: Allow nested BTF object to be refferenced by BTF object + offset Jiri Olsa
2020-06-30 1:52 ` Andrii Nakryiko
2020-06-30 13:54 ` Jiri Olsa
2020-06-30 20:05 ` Andrii Nakryiko
2020-06-30 20:07 ` Andrii Nakryiko
2020-07-02 10:08 ` Jiri Olsa
2020-07-06 23:15 ` Andrii Nakryiko
2020-06-25 22:12 ` [PATCH v4 bpf-next 08/14] bpf: Add BTF_SET_START/END macros Jiri Olsa
2020-06-26 21:49 ` Andrii Nakryiko
2020-06-25 22:12 ` [PATCH v4 bpf-next 09/14] bpf: Add info about .BTF.ids section to btf.rst Jiri Olsa
2020-06-25 22:13 ` [PATCH v4 bpf-next 10/14] bpf: Add d_path helper Jiri Olsa
2020-06-26 20:38 ` Andrii Nakryiko
2020-06-28 19:42 ` Jiri Olsa [this message]
2020-07-16 23:13 ` KP Singh
2020-07-17 8:28 ` Jiri Olsa
2020-06-25 22:13 ` [PATCH v4 bpf-next 11/14] tools headers: Adopt verbatim copy of btf_ids.h from kernel sources Jiri Olsa
2020-06-26 21:51 ` Andrii Nakryiko
2020-06-25 22:13 ` [PATCH v4 bpf-next 12/14] selftests/bpf: Add verifier test for d_path helper Jiri Olsa
2020-06-30 1:30 ` Andrii Nakryiko
2020-06-25 22:13 ` [PATCH v4 bpf-next 13/14] selftests/bpf: Add " Jiri Olsa
2020-06-26 21:55 ` Andrii Nakryiko
2020-06-28 19:55 ` Jiri Olsa
2020-06-25 22:13 ` [PATCH v4 bpf-next 14/14] selftests/bpf: Add test for resolve_btfids Jiri Olsa
2020-06-30 1:43 ` Andrii Nakryiko
2020-06-30 14:27 ` Jiri Olsa
2020-06-30 18:13 ` Andrii Nakryiko
2020-06-30 1:54 ` [PATCH v4 bpf-next 00/14] bpf: Add d_path helper Andrii Nakryiko
2020-06-30 13:55 ` Jiri Olsa
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