tools: bpf: move the event reading loop to libbpf

There are two copies of event reading loop - in bpftool and
trace_helpers "library".  Consolidate them and move the code
to libbpf.  Return codes from trace_helpers are kept, but
renamed to include LIBBPF prefix.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 15 insertions, 51 deletions

diff --git a/tools/bpf/bpftool/map_perf_ring.c b/tools/bpf/bpftool/map_perf_ring.c
index 9ae4bb8a2cad..1832100d1b27 100644
--- a/tools/bpf/bpftool/map_perf_ring.c
+++ b/tools/bpf/bpftool/map_perf_ring.c
@@ -50,14 +50,15 @@ static void int_exit(int signo)
         stop = true;
 }
 
-static void
-print_bpf_output(struct event_ring_info *ring, struct perf_event_sample *e)
+static enum bpf_perf_event_ret print_bpf_output(void *event, void *priv)
 {
+        struct event_ring_info *ring = priv;
+        struct perf_event_sample *e = event;
         struct {
                 struct perf_event_header header;
                 __u64 id;
                 __u64 lost;
-        } *lost = (void *)e;
+        } *lost = event;
 
         if (json_output) {
                 jsonw_start_object(json_wtr);
@@ -96,60 +97,23 @@ print_bpf_output(struct event_ring_info *ring, struct perf_event_sample *e)
                                e->header.type, e->header.size);
                 }
         }
+
+        return LIBBPF_PERF_EVENT_CONT;
 }
 
 static void
 perf_event_read(struct event_ring_info *ring, void **buf, size_t *buf_len)
 {
-        volatile struct perf_event_mmap_page *header = ring->mem;
-        __u64 buffer_size = MMAP_PAGE_CNT * get_page_size();
-        __u64 data_tail = header->data_tail;
-        __u64 data_head = header->data_head;
-        void *base, *begin, *end;
-
-        asm volatile("" ::: "memory"); /* in real code it should be smp_rmb() */
-        if (data_head == data_tail)
-                return;
-
-        base = ((char *)header) + get_page_size();
-
-        begin = base + data_tail % buffer_size;
-        end = base + data_head % buffer_size;
-
-        while (begin != end) {
-                struct perf_event_sample *e;
-
-                e = begin;
-                if (begin + e->header.size > base + buffer_size) {
-                        long len = base + buffer_size - begin;
-
-                        if (*buf_len < e->header.size) {
-                                free(*buf);
-                                *buf = malloc(e->header.size);
-                                if (!*buf) {
-                                        fprintf(stderr,
-                                                "can't allocate memory");
-                                        stop = true;
-                                        return;
-                                }
-                                *buf_len = e->header.size;
-                        }
-
-                        memcpy(*buf, begin, len);
-                        memcpy(*buf + len, base, e->header.size - len);
-                        e = (void *)*buf;
-                        begin = base + e->header.size - len;
-                } else if (begin + e->header.size == base + buffer_size) {
-                        begin = base;
-                } else {
-                        begin += e->header.size;
-                }
-
-                print_bpf_output(ring, e);
+        enum bpf_perf_event_ret ret;
+
+        ret = bpf_perf_event_read_simple(ring->mem,
+                                         MMAP_PAGE_CNT * get_page_size(),
+                                         get_page_size(), buf, buf_len,
+                                         print_bpf_output, ring);
+        if (ret != LIBBPF_PERF_EVENT_CONT) {
+                fprintf(stderr, "perf read loop failed with %d\n", ret);
+                stop = true;
         }
-
-        __sync_synchronize(); /* smp_mb() */
-        header->data_tail = data_head;
 }
 
 static int perf_mmap_size(void)