ring_buffer: add paranoid check for buffer page
If for some strange reason the buffer_page gets bigger, or the page struct
gets smaller, I want to know this ASAP. The best way is to not let the
kernel compile.
This patch adds code to test the size of the struct buffer_page against the
page struct and will cause compile issues if the buffer_page ever gets bigger
than the page struct.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 830a293..95ca933 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -289,6 +289,12 @@
kfree(cpu_buffer);
}
+/*
+ * Causes compile errors if the struct buffer_page gets bigger
+ * than the struct page.
+ */
+extern int ring_buffer_page_too_big(void);
+
/**
* ring_buffer_alloc - allocate a new ring_buffer
* @size: the size in bytes that is needed.
@@ -305,6 +311,11 @@
int bsize;
int cpu;
+ /* Paranoid! Optimizes out when all is well */
+ if (sizeof(struct buffer_page) > sizeof(struct page))
+ ring_buffer_page_too_big();
+
+
/* keep it in its own cache line */
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
GFP_KERNEL);