linux-kernel - [PATCH v2 1/9] libbpf: Introduce bpf_map_get_fd_by_id

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Date:   Thu, 2 Jun 2022 16:37:40 +0200
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     <ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>,
        <kpsingh@...nel.org>
CC:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kselftest@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [PATCH v2 1/9] libbpf: Introduce bpf_map_get_fd_by_id_flags()

Introduce bpf_map_get_fd_by_id_flags(), to let a caller specify the open
flags needed for the operation. This could make an operation succeed, if
access to a map is restricted (i.e. it allows only certain operations).

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 tools/lib/bpf/bpf.c      | 8 +++++++-
 tools/lib/bpf/bpf.h      | 1 +
 tools/lib/bpf/libbpf.map | 1 +
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 240186aac8e6..33bac2006043 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -1047,18 +1047,24 @@ 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_flags(__u32 id, __u32 flags)
 {
 	union bpf_attr attr;
 	int fd;
 
 	memset(&attr, 0, sizeof(attr));
 	attr.map_id = id;
+	attr.open_flags = flags;
 
 	fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
+int bpf_map_get_fd_by_id(__u32 id)
+{
+	return bpf_map_get_fd_by_id_flags(id, 0);
+}
+
 int bpf_btf_get_fd_by_id(__u32 id)
 {
 	union bpf_attr attr;
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index cabc03703e29..20e4c852362d 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -438,6 +438,7 @@ 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);
 LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
+LIBBPF_API int bpf_map_get_fd_by_id_flags(__u32 id, __u32 flags);
 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 38e284ff057d..019278e66836 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -466,6 +466,7 @@ LIBBPF_1.0.0 {
 		libbpf_bpf_link_type_str;
 		libbpf_bpf_map_type_str;
 		libbpf_bpf_prog_type_str;
+		bpf_map_get_fd_by_id_flags;
 
 	local: *;
 };
-- 
2.25.1