linux-kernel - [PATCH] [PATCH bpf-next] libbpf: Add bpf_obj_get

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Date:   Mon, 18 Jul 2022 21:46:33 +0000
From:   Joe Burton <jevburton.kernel@...il.com>
To:     Andrii Nakryiko <andrii@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Joe Burton <jevburton@...gle.com>
Subject: [PATCH] [PATCH bpf-next] libbpf: Add bpf_obj_get_opts()

From: Joe Burton <jevburton@...gle.com>

Add an extensible variant of bpf_obj_get() capable of setting the
`file_flags` parameter.

This parameter is needed to enable unprivileged access to BPF maps.
Without a method like this, users must manually make the syscall.

Signed-off-by: Joe Burton <jevburton@...gle.com>
---
 tools/lib/bpf/bpf.c | 10 ++++++++++
 tools/lib/bpf/bpf.h |  9 +++++++++
 2 files changed, 19 insertions(+)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 5eb0df90eb2b..5acb0e8bd13c 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -578,12 +578,22 @@ int bpf_obj_pin(int fd, const char *pathname)
 }
 
 int bpf_obj_get(const char *pathname)
+{
+	LIBBPF_OPTS(bpf_obj_get_opts, opts);
+	return bpf_obj_get_opts(pathname, &opts);
+}
+
+int bpf_obj_get_opts(const char *pathname, const struct bpf_obj_get_opts *opts)
 {
 	union bpf_attr attr;
 	int fd;
 
+	if (!OPTS_VALID(opts, bpf_obj_get_opts))
+		return libbpf_err(-EINVAL);
+
 	memset(&attr, 0, sizeof(attr));
 	attr.pathname = ptr_to_u64((void *)pathname);
+	attr.file_flags = OPTS_GET(opts, file_flags, 0);
 
 	fd = sys_bpf_fd(BPF_OBJ_GET, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 88a7cc4bd76f..f31b493b5f9a 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -270,8 +270,17 @@ LIBBPF_API int bpf_map_update_batch(int fd, const void *keys, const void *values
 				    __u32 *count,
 				    const struct bpf_map_batch_opts *opts);
 
+struct bpf_obj_get_opts {
+	size_t sz; /* size of this struct for forward/backward compatibility */
+
+	__u32 file_flags;
+};
+#define bpf_obj_get_opts__last_field file_flags
+
 LIBBPF_API int bpf_obj_pin(int fd, const char *pathname);
 LIBBPF_API int bpf_obj_get(const char *pathname);
+LIBBPF_API int bpf_obj_get_opts(const char *pathname,
+				const struct bpf_obj_get_opts *opts);
 
 struct bpf_prog_attach_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
-- 
2.37.0.170.g444d1eabd0-goog