Re: [PATCH bpf-next v7 6/8] libbpf: Update a bpf_link with another struct_ops.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 3/15/23 7:36 PM, Kui-Feng Lee wrote:
Introduce bpf_link__update_map(), which allows to atomically update
underlying struct_ops implementation for given struct_ops BPF link

Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxxxx>
---
  tools/lib/bpf/libbpf.c   | 30 ++++++++++++++++++++++++++++++
  tools/lib/bpf/libbpf.h   |  1 +
  tools/lib/bpf/libbpf.map |  1 +
  3 files changed, 32 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6dbae7ffab48..63ec1f8fe8a0 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11659,6 +11659,36 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
  	return &link->link;
  }
+/*
+ * Swap the back struct_ops of a link with a new struct_ops map.
+ */
+int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map)
+{
+	struct bpf_link_struct_ops *st_ops_link;
+	__u32 zero = 0;
+	int err, fd;
+
+	if (!bpf_map__is_struct_ops(map) || map->fd < 0)
+		return -EINVAL;
+
+	st_ops_link = container_of(link, struct bpf_link_struct_ops, link);
+	/* Ensure the type of a link is correct */
+	if (st_ops_link->map_fd < 0)
+		return -EINVAL;
+
+	err = bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0);
+	if (err && err != -EBUSY)
+		return err;
+
+	fd = bpf_link_update(link->fd, map->fd, NULL);

bpf_link_update() returns ok/error. Using "fd = ..." is confusing. Use "err = ..." instead and remove the need of "int fd;".

+	if (fd < 0)
+		return fd;
+
+	st_ops_link->map_fd = map->fd;
+
+	return 0;
+}
+
  typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct perf_event_header *hdr,
  							  void *private_data);
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index db4992a036f8..1615e55e2e79 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -719,6 +719,7 @@ bpf_program__attach_freplace(const struct bpf_program *prog,
  struct bpf_map;
LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map);
+LIBBPF_API int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map);
struct bpf_iter_attach_opts {
  	size_t sz; /* size of this struct for forward/backward compatibility */
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 50dde1f6521e..cc05be376257 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -387,6 +387,7 @@ LIBBPF_1.2.0 {
  	global:
  		bpf_btf_get_info_by_fd;
  		bpf_link_get_info_by_fd;
+		bpf_link__update_map;
  		bpf_map_get_info_by_fd;
  		bpf_prog_get_info_by_fd;
  } LIBBPF_1.1.0;




[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux