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bpf, libbpf: simplify and cleanup perf ring buffer walk

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Simplify bpf_perf_event_read_simple() a bit and fix up some minor
things along the way: the return code in the header is not of type
int but enum bpf_perf_event_ret instead. Once callback indicated
to break the loop walking event data, it also needs to be consumed
in data_tail since it has been processed already.

Moreover, bpf_perf_event_print_t callback should avoid void * as
we actually get a pointer to struct perf_event_header and thus
applications can make use of container_of() to have type checks.
The walk also doesn't have to use modulo op since the ring size is
required to be power of two.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann
2018-10-21 02:09:28 +02:00
committed by Alexei Starovoitov
parent 84430d4232
commit 3dca21156b
4 changed files with 44 additions and 49 deletions
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10
tools/bpf/bpftool/map_perf_ring.c
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@@ -50,15 +50,17 @@ static void int_exit(int signo)
stop = true;
}
static enum bpf_perf_event_ret print_bpf_output(void *event, void *priv)
static enum bpf_perf_event_ret
print_bpf_output(struct perf_event_header *event, void *private_data)
{
struct event_ring_info *ring = priv;
struct perf_event_sample *e = event;
struct perf_event_sample *e = container_of(event, struct perf_event_sample,
header);
struct event_ring_info *ring = private_data;
struct {
struct perf_event_header header;
__u64 id;
__u64 lost;
} *lost = event;
} *lost = (typeof(lost))event;
if (json_output) {
jsonw_start_object(json_wtr);