[PATCH 02/20] fgraph: Use BUILD_BUG_ON() to make sure we have structures divisible by long

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>

Instead of using "ALIGN()", use BUILD_BUG_ON() as the structures should
always be divisible by sizeof(long).

Co-developed with Masami Hiramatsu:
Link: https://lore.kernel.org/linux-trace-kernel/171509093949.162236.14518699447151894536.stgit@devnote2
Link: http://lkml.kernel.org/r/20190524111144.GI2589@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/fgraph.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index c62e6db718a0..fdb206aeffe3 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -33,7 +33,7 @@
  * SHADOW_STACK_MAX_OFFSET: The max offset of the stack for a new frame to be added
  */
 #define FGRAPH_FRAME_SIZE	sizeof(struct ftrace_ret_stack)
-#define FGRAPH_FRAME_OFFSET	(ALIGN(FGRAPH_FRAME_SIZE, sizeof(long)) / sizeof(long))
+#define FGRAPH_FRAME_OFFSET	DIV_ROUND_UP(FGRAPH_FRAME_SIZE, sizeof(long))
 #define SHADOW_STACK_SIZE (PAGE_SIZE)
 #define SHADOW_STACK_OFFSET			\
 	(ALIGN(SHADOW_STACK_SIZE, sizeof(long)) / sizeof(long))
@@ -103,6 +103,8 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
 	if (!current->ret_stack)
 		return -EBUSY;
 
+	BUILD_BUG_ON(SHADOW_STACK_SIZE % sizeof(long));
+
 	/*
 	 * We must make sure the ret_stack is tested before we read
 	 * anything else.
@@ -326,6 +328,8 @@ ftrace_graph_get_ret_stack(struct task_struct *task, int idx)
 {
 	int index = task->curr_ret_stack;
 
+	BUILD_BUG_ON(FGRAPH_FRAME_SIZE % sizeof(long));
+
 	index -= FGRAPH_FRAME_OFFSET * (idx + 1);
 	if (index < 0)
 		return NULL;
-- 
2.43.0