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authorSong Liu <songliubraving@fb.com>2020-09-30 15:49:26 -0700
committerAlexei Starovoitov <ast@kernel.org>2020-09-30 23:18:12 -0700
commit792caccc4526bb489e054f9ab61d7c024b15dea2 (patch)
tree3a37926e19cd8a4ad165269eb80c7b8d2096414e
parent3effc06a4dde3e2f6ee3d82e59d97ec357802a4b (diff)
bpf: Introduce BPF_F_PRESERVE_ELEMS for perf event array
Currently, perf event in perf event array is removed from the array when the map fd used to add the event is closed. This behavior makes it difficult to the share perf events with perf event array. Introduce perf event map that keeps the perf event open with a new flag BPF_F_PRESERVE_ELEMS. With this flag set, perf events in the array are not removed when the original map fd is closed. Instead, the perf event will stay in the map until 1) it is explicitly removed from the array; or 2) the array is freed. Signed-off-by: Song Liu <songliubraving@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200930224927.1936644-2-songliubraving@fb.com
-rw-r--r--include/uapi/linux/bpf.h3
-rw-r--r--kernel/bpf/arraymap.c19
-rw-r--r--tools/include/uapi/linux/bpf.h3
3 files changed, 23 insertions, 2 deletions
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 1f17c6752deb..4f556cfcbfbe 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -414,6 +414,9 @@ enum {
/* Enable memory-mapping BPF map */
BPF_F_MMAPABLE = (1U << 10),
+
+/* Share perf_event among processes */
+ BPF_F_PRESERVE_ELEMS = (1U << 11),
};
/* Flags for BPF_PROG_QUERY. */
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index e5fd31268ae0..bd777dd6f967 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -15,7 +15,8 @@
#include "map_in_map.h"
#define ARRAY_CREATE_FLAG_MASK \
- (BPF_F_NUMA_NODE | BPF_F_MMAPABLE | BPF_F_ACCESS_MASK)
+ (BPF_F_NUMA_NODE | BPF_F_MMAPABLE | BPF_F_ACCESS_MASK | \
+ BPF_F_PRESERVE_ELEMS)
static void bpf_array_free_percpu(struct bpf_array *array)
{
@@ -64,6 +65,10 @@ int array_map_alloc_check(union bpf_attr *attr)
attr->map_flags & BPF_F_MMAPABLE)
return -EINVAL;
+ if (attr->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY &&
+ attr->map_flags & BPF_F_PRESERVE_ELEMS)
+ return -EINVAL;
+
if (attr->value_size > KMALLOC_MAX_SIZE)
/* if value_size is bigger, the user space won't be able to
* access the elements.
@@ -1134,6 +1139,9 @@ static void perf_event_fd_array_release(struct bpf_map *map,
struct bpf_event_entry *ee;
int i;
+ if (map->map_flags & BPF_F_PRESERVE_ELEMS)
+ return;
+
rcu_read_lock();
for (i = 0; i < array->map.max_entries; i++) {
ee = READ_ONCE(array->ptrs[i]);
@@ -1143,12 +1151,19 @@ static void perf_event_fd_array_release(struct bpf_map *map,
rcu_read_unlock();
}
+static void perf_event_fd_array_map_free(struct bpf_map *map)
+{
+ if (map->map_flags & BPF_F_PRESERVE_ELEMS)
+ bpf_fd_array_map_clear(map);
+ fd_array_map_free(map);
+}
+
static int perf_event_array_map_btf_id;
const struct bpf_map_ops perf_event_array_map_ops = {
.map_meta_equal = bpf_map_meta_equal,
.map_alloc_check = fd_array_map_alloc_check,
.map_alloc = array_map_alloc,
- .map_free = fd_array_map_free,
+ .map_free = perf_event_fd_array_map_free,
.map_get_next_key = array_map_get_next_key,
.map_lookup_elem = fd_array_map_lookup_elem,
.map_delete_elem = fd_array_map_delete_elem,
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 1f17c6752deb..4f556cfcbfbe 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -414,6 +414,9 @@ enum {
/* Enable memory-mapping BPF map */
BPF_F_MMAPABLE = (1U << 10),
+
+/* Share perf_event among processes */
+ BPF_F_PRESERVE_ELEMS = (1U << 11),
};
/* Flags for BPF_PROG_QUERY. */