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>

3 files changed, 75 insertions, 1 deletions

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index e6d5f8d1477f..f3fab4af4260 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -69,7 +69,7 @@ FEATURE_USER = .libbpf
 FEATURE_TESTS = libelf libelf-getphdrnum libelf-mmap bpf
 FEATURE_DISPLAY = libelf bpf
 
-INCLUDES = -I. -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(ARCH)/include/uapi -I$(srctree)/tools/include/uapi
+INCLUDES = -I. -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(ARCH)/include/uapi -I$(srctree)/tools/include/uapi -I$(srctree)/tools/perf
 FEATURE_CHECK_CFLAGS-bpf = $(INCLUDES)
 
 check_feat := 1
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7bcdca13083a..ce96f1fe3f37 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -31,6 +31,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <perf-sys.h>
 #include <asm/unistd.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
@@ -2210,3 +2211,63 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
         *prog_fd = bpf_program__fd(first_prog);
         return 0;
 }
+
+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)
+{
+        volatile struct perf_event_mmap_page *header = mem;
+        __u64 data_tail = header->data_tail;
+        __u64 data_head = header->data_head;
+        void *base, *begin, *end;
+        int ret;
+
+        asm volatile("" ::: "memory"); /* in real code it should be smp_rmb() */
+        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) {
+                                        ret = LIBBPF_PERF_EVENT_ERROR;
+                                        break;
+                                }
+                                *buf_len = 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;
+                }
+
+                ret = fn(ehdr, priv);
+                if (ret != LIBBPF_PERF_EVENT_CONT)
+                        break;
+
+                data_tail += ehdr->size;
+        }
+
+        __sync_synchronize(); /* smp_mb() */
+        header->data_tail = data_tail;
+
+        return ret;
+}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 197f9ce2248c..ce681097584e 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -267,4 +267,17 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
                   struct bpf_object **pobj, int *prog_fd);
 
 int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags);
+
+enum bpf_perf_event_ret {
+        LIBBPF_PERF_EVENT_DONE  = 0,
+        LIBBPF_PERF_EVENT_ERROR = -1,
+        LIBBPF_PERF_EVENT_CONT  = -2,
+};
+
+typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(void *event,
+                                                          void *priv);
+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);
 #endif