ring-buffer: Add ring_buffer_alloc_range()

In preparation to allowing the trace ring buffer to be allocated in a
range of memory that is persistent across reboots, add
ring_buffer_alloc_range(). It takes a contiguous range of memory and will
split it up evenly for the per CPU ring buffers.

If there's not enough memory to handle all CPUs with the minimum size, it
will fail to allocate the ring buffer.

Link: https://lkml.kernel.org/r/[email protected]

Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Vincent Donnefort <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Daniel Bristot de Oliveira <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vineeth Pillai <[email protected]>
Cc: Youssef Esmat <[email protected]>
Cc: Beau Belgrave <[email protected]>
Cc: Alexander Graf <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: David Howells <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Kees Cook <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 96d2140b471e..a50b0223b1d3 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -89,6 +89,11 @@ void ring_buffer_discard_commit(struct trace_buffer *buffer,
 struct trace_buffer *
 __ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *key);
 
+struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flags,
+					       int order, unsigned long start,
+					       unsigned long range_size,
+					       struct lock_class_key *key);
+
 /*
  * Because the ring buffer is generic, if other users of the ring buffer get
  * traced by ftrace, it can produce lockdep warnings. We need to keep each
@@ -100,6 +105,18 @@ __ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *k
 	__ring_buffer_alloc((size), (flags), &__key);	\
 })
 
+/*
+ * Because the ring buffer is generic, if other users of the ring buffer get
+ * traced by ftrace, it can produce lockdep warnings. We need to keep each
+ * ring buffer's lock class separate.
+ */
+#define ring_buffer_alloc_range(size, flags, order, start, range_size)	\
+({									\
+	static struct lock_class_key __key;				\
+	__ring_buffer_alloc_range((size), (flags), (order), (start),	\
+				  (range_size), &__key);		\
+})
+
 typedef bool (*ring_buffer_cond_fn)(void *data);
 int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full,
 		     ring_buffer_cond_fn cond, void *data);