On 2015/7/23 8:48, Alexei Starovoitov wrote:
On 7/22/15 1:09 AM, Kaixu Xia wrote:
Introduce a new bpf map type 'BPF_MAP_TYPE_PERF_EVENT_ARRAY'.
This map will only store the pointer to struct perf_event.
Signed-off-by: Kaixu Xia <xiaka...@huawei.com>
---
include/linux/bpf.h | 2 ++
include/uapi/linux/bpf.h | 1 +
kernel/bpf/arraymap.c | 40 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 43 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4383476..f6a2442 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -11,6 +11,8 @@
#include <linux/workqueue.h>
#include <linux/file.h>
+#define MAX_PERF_EVENT_ARRAY_ENTRY (2*NR_CPUS)
why this artificial limit?
Just drop it.
Then we should find another way to prevent user create a large map but
only use
a small portion of it, since normal array map can't report whether a
slot is used
or not. When releasing the map, we have to release each perf event.
Currently the only
way is to check map value in each slot.
+static struct bpf_map *perf_event_array_map_alloc(union bpf_attr *attr)
+{
+ /* only the pointer to struct perf_event can be stored in
+ * perf_event_array map
+ */
+ if (attr->value_size != sizeof(void *))
+ return ERR_PTR(-EINVAL);
hmm. that's odd. why reinvent things? please do the same as
prog_array does. Namely below:
+static const struct bpf_map_ops perf_event_array_ops = {
+ .map_alloc = perf_event_array_map_alloc,
+ .map_free = array_map_free,
+ .map_get_next_key = perf_event_array_map_get_next_key,
+ .map_lookup_elem = array_map_lookup_elem,
+ .map_delete_elem = array_map_delete_elem,
this is broken. you don't want programs to manipulate
'struct perf_event *' pointers.
lookup/update/delete helpers shouldn't be accessible from the programs
then update/delete can be cleanly implemented and called via syscall.
See how prog_array does it.
Also please collapse patches 1-3 into one. Their logically one piece.
I'll comment on them as well, but it would have been easier for me
and you if their were part of one email thread.
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