[PATCH v1 1/1] libbpf: perfbuf: allow raw access to buffers

[Jon Doron <arilou@gmail.com>]

From: Jon Doron <jond@wiz.io>

Add API for perfbuf to support writing a custom event reader.

Signed-off-by: Jon Doron <jond@wiz.io>
---
 tools/lib/bpf/libbpf.c | 40 ++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h |  6 ++++++
 2 files changed, 46 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e89cc9c885b3..37299aa05185 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -12433,6 +12433,46 @@ static int perf_buffer__process_records(struct perf_buffer *pb,
 	return 0;
 }
 
+int perf_buffer__raw_ring_buf(const struct perf_buffer *pb, size_t buf_idx,
+			      void **base, size_t *buf_size, __u64 *head,
+			      __u64 *tail)
+{
+	struct perf_cpu_buf *cpu_buf;
+	struct perf_event_mmap_page *header;
+
+	if (buf_idx >= pb->cpu_cnt)
+		return libbpf_err(-EINVAL);
+
+	cpu_buf = pb->cpu_bufs[buf_idx];
+	if (!cpu_buf)
+		return libbpf_err(-ENOENT);
+
+	header = cpu_buf->base;
+	*head = ring_buffer_read_head(header);
+	*tail = header->data_tail;
+	*base = ((__u8 *)header) + pb->page_size;
+	*buf_size = pb->mmap_size;
+	return 0;
+}
+
+int perf_buffer__set_ring_buf_tail(const struct perf_buffer *pb, size_t buf_idx,
+				   __u64 tail)
+{
+	struct perf_cpu_buf *cpu_buf;
+	struct perf_event_mmap_page *header;
+
+	if (buf_idx >= pb->cpu_cnt)
+		return libbpf_err(-EINVAL);
+
+	cpu_buf = pb->cpu_bufs[buf_idx];
+	if (!cpu_buf)
+		return libbpf_err(-ENOENT);
+
+	header = cpu_buf->base;
+	ring_buffer_write_tail(header, tail);
+	return 0;
+}
+
 int perf_buffer__epoll_fd(const struct perf_buffer *pb)
 {
 	return pb->epoll_fd;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 9e9a3fd3edd8..b6f6b6a12d70 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1381,6 +1381,12 @@ LIBBPF_API int perf_buffer__consume(struct perf_buffer *pb);
 LIBBPF_API int perf_buffer__consume_buffer(struct perf_buffer *pb, size_t buf_idx);
 LIBBPF_API size_t perf_buffer__buffer_cnt(const struct perf_buffer *pb);
 LIBBPF_API int perf_buffer__buffer_fd(const struct perf_buffer *pb, size_t buf_idx);
+LIBBPF_API int perf_buffer__raw_ring_buf(const struct perf_buffer *pb,
+					 size_t buf_idx, void **base,
+					 size_t *buf_size, __u64 *head,
+					 __u64 *tail);
+LIBBPF_API int perf_buffer__set_ring_buf_tail(const struct perf_buffer *pb,
+					      size_t buf_idx, __u64 tail);
 
 typedef enum bpf_perf_event_ret
 	(*bpf_perf_event_print_t)(struct perf_event_header *hdr,
-- 
2.36.1