From: Grant Seltzer <grantseltzer@xxxxxxxxx>
This adds a new API function used to retrieve all data from a
percpu array or percpu hashmap.
This is useful because the current interface for doing so
requires knowledge of the layout of these BPF map internal
structures.
Signed-off-by: Grant Seltzer <grantseltzer@xxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 28 ++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.h | 25 +++++++++++++++++++++++++
2 files changed, 53 insertions(+)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 873a29ce7781..8d72cff22688 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -36,6 +36,7 @@
#include <linux/perf_event.h>
#include <linux/ring_buffer.h>
#include <linux/version.h>
+#include <linux/math.h>
#include <sys/epoll.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
@@ -4370,6 +4371,33 @@ int bpf_map__resize(struct bpf_map *map, __u32 max_entries)
return bpf_map__set_max_entries(map, max_entries);
}
+void *bpf_map__get_percpu_value(const struct bpf_map *map, const void *key)
+{
+
+ if (!(bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY ||
+ bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_HASH)) {
+ return libbpf_err_ptr(-EINVAL);
+ }
+
+ int num_cpus;
+ __u32 value_size;
+ num_cpus = libbpf_num_possible_cpus();
+
+ if (num_cpus < 0)
+ return libbpf_err_ptr(-EBUSY);
+
+ value_size = bpf_map__value_size(map);
+
+ void *data = malloc(roundup(value_size, 8) * num_cpus);
+ int err = bpf_map_lookup_elem(map->fd, key, data);
+ if (err) {
+ free(data);
+ return libbpf_err_ptr(err);
+ }
+
+ return data;
+}
+
static int
bpf_object__probe_loading(struct bpf_object *obj)
{
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index cdbfee60ea3e..99b218702dfb 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -921,6 +921,31 @@ LIBBPF_API const void *bpf_map__initial_value(struct bpf_map *map, size_t *psize
LIBBPF_DEPRECATED_SINCE(0, 8, "use bpf_map__type() instead")
LIBBPF_API bool bpf_map__is_offload_neutral(const struct bpf_map *map);
+/**
+ * @brief **bpf_map__get_percpu_value()** returns a pointer to an array
+ * of data stored in a per-cpu array or per-cpu hashmap at a specified
+ * key. Each element is padded to 8 bytes regardless of the value data
+ * type stored in the per-cpu map. The index of each element in the array
+ * corresponds with the cpu that the data was set from.
+ * @param map per-cpu array or per-cpu hashmap
+ * @param key the key or index in the map
+ * @return pointer to the array of data
+ *
+ * example usage:
+ *
+ * values = bpf_map__get_percpu_value(bpfmap, (void*)&zero);
+ * if (values == NULL) {
+ * // error handling
+ * }
+ *
+ * void* ptr = values;
+ * for (int i = 0; i < num_cpus; i++) {
+ * printf("CPU %d: %ld\n", i, *(ulong*)ptr);
+ * ptr += 8;
+ * }
+ */
+LIBBPF_API void *bpf_map__get_percpu_value(const struct bpf_map *map, const void *key);
+
/**
* @brief **bpf_map__is_internal()** tells the caller whether or not the
* passed map is a special map created by libbpf automatically for things like
--
2.34.1
