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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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15
tools/lib/bpf/libbpf.h
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@ -297,13 +297,14 @@ enum bpf_perf_event_ret {
LIBBPF_PERF_EVENT_CONT = -2,
};
typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(void *event,
void *priv);
LIBBPF_API int bpf_perf_event_read_simple(void *mem, unsigned long size,
unsigned long page_size,
void **buf, size_t *buf_len,
bpf_perf_event_print_t fn,
void *priv);
struct perf_event_header;
typedef enum bpf_perf_event_ret
(*bpf_perf_event_print_t)(struct perf_event_header *hdr,
void *private_data);
LIBBPF_API enum bpf_perf_event_ret
bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
void **copy_mem, size_t *copy_size,
bpf_perf_event_print_t fn, void *private_data);
struct nlattr;
typedef int (*libbpf_dump_nlmsg_t)(void *cookie, void *msg, struct nlattr **tb);