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Fri, 30 Sep 2022 13:51:01 -0700 (PDT) MIME-Version: 1.0 References: <20220926154430.1552800-1-roberto.sassu@huaweicloud.com> <20220926154430.1552800-2-roberto.sassu@huaweicloud.com> In-Reply-To: <20220926154430.1552800-2-roberto.sassu@huaweicloud.com> From: Andrii Nakryiko Date: Fri, 30 Sep 2022 13:50:49 -0700 Message-ID: Subject: Re: [RFC][PATCH 1/3] libbpf: Define bpf_get_fd_opts and introduce bpf_map_get_fd_by_id_opts() To: Roberto Sassu Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, mykolal@fb.com, shuah@kernel.org, oss@lmb.io, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, fengc@google.com, davem@davemloft.net Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Mon, Sep 26, 2022 at 8:45 AM Roberto Sassu wrote: > > From: Roberto Sassu > > Define a new data structure called bpf_get_fd_opts, with the member > open_flags, to be used by callers of the _opts variants of > bpf_*_get_fd_by_id() to specify the permissions needed for the file > descriptor to be obtained. > > Also, introduce bpf_map_get_fd_by_id_opts(), to let the caller pass a > bpf_get_fd_opts structure. > > Finally, keep the existing bpf_map_get_fd_by_id(), and call > bpf_map_get_fd_by_id_opts() with NULL as opts argument, to request > read-write permissions (current behavior). > > Signed-off-by: Roberto Sassu > --- looks good overall, but please see two nits below > tools/lib/bpf/bpf.c | 12 +++++++++++- > tools/lib/bpf/bpf.h | 10 ++++++++++ > tools/lib/bpf/libbpf.map | 3 ++- > 3 files changed, 23 insertions(+), 2 deletions(-) > > diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c > index 1d49a0352836..4b03063edf1d 100644 > --- a/tools/lib/bpf/bpf.c > +++ b/tools/lib/bpf/bpf.c > @@ -948,19 +948,29 @@ int bpf_prog_get_fd_by_id(__u32 id) > return libbpf_err_errno(fd); > } > > -int bpf_map_get_fd_by_id(__u32 id) > +int bpf_map_get_fd_by_id_opts(__u32 id, > + const struct bpf_get_fd_opts *opts) > { > const size_t attr_sz = offsetofend(union bpf_attr, open_flags); > union bpf_attr attr; > int fd; > > + if (!OPTS_VALID(opts, bpf_get_fd_opts)) > + return libbpf_err(-EINVAL); > + > memset(&attr, 0, attr_sz); > attr.map_id = id; > + attr.open_flags = OPTS_GET(opts, open_flags, 0); > > fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, attr_sz); > return libbpf_err_errno(fd); > } > > +int bpf_map_get_fd_by_id(__u32 id) > +{ > + return bpf_map_get_fd_by_id_opts(id, NULL); > +} > + > int bpf_btf_get_fd_by_id(__u32 id) > { > const size_t attr_sz = offsetofend(union bpf_attr, open_flags); > diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h > index 9c50beabdd14..38a1b7eccfc8 100644 > --- a/tools/lib/bpf/bpf.h > +++ b/tools/lib/bpf/bpf.h > @@ -365,7 +365,17 @@ LIBBPF_API int bpf_prog_get_next_id(__u32 start_id, __u32 *next_id); > LIBBPF_API int bpf_map_get_next_id(__u32 start_id, __u32 *next_id); > LIBBPF_API int bpf_btf_get_next_id(__u32 start_id, __u32 *next_id); > LIBBPF_API int bpf_link_get_next_id(__u32 start_id, __u32 *next_id); > + > +struct bpf_get_fd_opts { > + size_t sz; /* size of this struct for forward/backward compatibility */ > + __u32 open_flags; /* permissions requested for the operation on fd */ > + __u32 :0; this should be size_t: 0 > +}; > +#define bpf_get_fd_opts__last_field open_flags > + > LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id); > +LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id, > + const struct bpf_get_fd_opts *opts); > LIBBPF_API int bpf_map_get_fd_by_id(__u32 id); > LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id); > LIBBPF_API int bpf_link_get_fd_by_id(__u32 id); > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map > index c1d6aa7c82b6..2e665b21d84f 100644 > --- a/tools/lib/bpf/libbpf.map > +++ b/tools/lib/bpf/libbpf.map > @@ -367,10 +367,11 @@ LIBBPF_1.0.0 { > libbpf_bpf_map_type_str; > libbpf_bpf_prog_type_str; > perf_buffer__buffer; > -}; > +} LIBBPF_0.8.0; > good catch, please send this as a separate fix, thanks! > LIBBPF_1.1.0 { > global: > + bpf_map_get_fd_by_id_opts; > user_ring_buffer__discard; > user_ring_buffer__free; > user_ring_buffer__new; > -- > 2.25.1 >