From 3dca21156b5f809510e8c3efe7f1046e27242e3d Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sun, 21 Oct 2018 02:09:28 +0200 Subject: bpf, libbpf: simplify and cleanup perf ring buffer walk 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 Signed-off-by: Alexei Starovoitov --- tools/bpf/bpftool/map_perf_ring.c | 10 +++-- tools/lib/bpf/libbpf.c | 67 +++++++++++++---------------- tools/lib/bpf/libbpf.h | 15 ++++--- tools/testing/selftests/bpf/trace_helpers.c | 7 +-- 4 files changed, 47 insertions(+), 52 deletions(-) (limited to 'tools') diff --git a/tools/bpf/bpftool/map_perf_ring.c b/tools/bpf/bpftool/map_perf_ring.c index 6d41323be291..bdaf4062e26e 100644 --- a/tools/bpf/bpftool/map_perf_ring.c +++ b/tools/bpf/bpftool/map_perf_ring.c @@ -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); diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 0c21355f04a7..b607be7236d3 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -2415,56 +2415,47 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr, } enum bpf_perf_event_ret -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) +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 perf_event_mmap_page *header = mem; + struct perf_event_mmap_page *header = mmap_mem; __u64 data_head = ring_buffer_read_head(header); __u64 data_tail = header->data_tail; - int ret = LIBBPF_PERF_EVENT_ERROR; - void *base, *begin, *end; - - if (data_head == data_tail) - return LIBBPF_PERF_EVENT_CONT; - - base = ((char *)header) + page_size; - - begin = base + data_tail % size; - end = base + data_head % size; - - while (begin != end) { - struct perf_event_header *ehdr; - - ehdr = begin; - if (begin + ehdr->size > base + size) { - long len = base + size - begin; - - if (*buf_len < ehdr->size) { - free(*buf); - *buf = malloc(ehdr->size); - if (!*buf) { + void *base = ((__u8 *)header) + page_size; + int ret = LIBBPF_PERF_EVENT_CONT; + struct perf_event_header *ehdr; + size_t ehdr_size; + + while (data_head != data_tail) { + ehdr = base + (data_tail & (mmap_size - 1)); + ehdr_size = ehdr->size; + + if (((void *)ehdr) + ehdr_size > base + mmap_size) { + void *copy_start = ehdr; + size_t len_first = base + mmap_size - copy_start; + size_t len_secnd = ehdr_size - len_first; + + if (*copy_size < ehdr_size) { + free(*copy_mem); + *copy_mem = malloc(ehdr_size); + if (!*copy_mem) { + *copy_size = 0; ret = LIBBPF_PERF_EVENT_ERROR; break; } - *buf_len = ehdr->size; + *copy_size = ehdr_size; } - memcpy(*buf, begin, len); - memcpy(*buf + len, base, ehdr->size - len); - ehdr = (void *)*buf; - begin = base + ehdr->size - len; - } else if (begin + ehdr->size == base + size) { - begin = base; - } else { - begin += ehdr->size; + memcpy(*copy_mem, copy_start, len_first); + memcpy(*copy_mem + len_first, base, len_secnd); + ehdr = *copy_mem; } - ret = fn(ehdr, priv); + ret = fn(ehdr, private_data); + data_tail += ehdr_size; if (ret != LIBBPF_PERF_EVENT_CONT) break; - - data_tail += ehdr->size; } ring_buffer_write_tail(header, data_tail); diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 1354cc9f8cba..1f3468dad8b2 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -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); diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c index a3d1dace4a75..4cdb63bf0521 100644 --- a/tools/testing/selftests/bpf/trace_helpers.c +++ b/tools/testing/selftests/bpf/trace_helpers.c @@ -125,10 +125,11 @@ struct perf_event_sample { char data[]; }; -static enum bpf_perf_event_ret bpf_perf_event_print(void *event, void *priv) +static enum bpf_perf_event_ret +bpf_perf_event_print(struct perf_event_header *hdr, void *private_data) { - struct perf_event_sample *e = event; - perf_event_print_fn fn = priv; + struct perf_event_sample *e = (struct perf_event_sample *)hdr; + perf_event_print_fn fn = private_data; int ret; if (e->header.type == PERF_RECORD_SAMPLE) { -- cgit v1.2.3-59-g8ed1b