1 files changed, 20 insertions, 4 deletions

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 0670742b2d60..eac3e9080c3c 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -3,8 +3,9 @@
 #define _LINUX_RING_BUFFER_H
 
 #include <linux/mm.h>
-#include <linux/seq_file.h>
 #include <linux/poll.h>
+#include <linux/ring_buffer_types.h>
+#include <linux/seq_file.h>
 
 #include <uapi/linux/trace_mmap.h>
 
@@ -218,14 +219,15 @@ bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer);
 size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu);
 
 struct buffer_data_read_page;
-struct buffer_data_read_page *
-ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu);
+int ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu,
+				struct buffer_data_read_page **rpage);
 void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
 				struct buffer_data_read_page *page);
 int ring_buffer_read_page(struct trace_buffer *buffer,
 			  struct buffer_data_read_page *data_page,
 			  size_t len, int cpu, int full);
 void *ring_buffer_read_page_data(struct buffer_data_read_page *page);
+unsigned int ring_buffer_read_page_size(struct buffer_data_read_page *rpage);
 
 struct trace_seq;
 
@@ -278,11 +280,25 @@ static inline struct ring_buffer_desc *__first_ring_buffer_desc(struct trace_buf
 	return (struct ring_buffer_desc *)(&desc->__data[0]);
 }
 
+/*
+ * Returns the number of pages for a ring_buffer_desc. The caller must ensure it
+ * does not overflow ring_buffer_desc::nr_page_va.
+ */
+static inline unsigned long __calc_nr_pages_ring_buffer_desc(size_t size)
+{
+	/* Takes into account the reader page */
+	return max(DIV_ROUND_UP(size, PAGE_SIZE - BUF_PAGE_HDR_SIZE), 2UL) + 1;
+}
+
 static inline size_t trace_buffer_desc_size(size_t buffer_size, unsigned int nr_cpus)
 {
-	unsigned int nr_pages = max(DIV_ROUND_UP(buffer_size, PAGE_SIZE), 2UL) + 1;
+	unsigned long nr_pages = __calc_nr_pages_ring_buffer_desc(buffer_size);
 	struct ring_buffer_desc *rbdesc;
 
+	/* Capped by ring_buffer_desc::nr_page_va */
+	if (nr_pages > UINT_MAX)
+		return SIZE_MAX;
+
 	return size_add(offsetof(struct trace_buffer_desc, __data),
 			size_mul(nr_cpus, struct_size(rbdesc, page_va, nr_pages)));
 }