[PATCH v4 04/33] fgraph: Use BUILD_BUG_ON() to make sure we have structures divisible by long

Masami Hiramatsu (Google)
2023-12-08T10:25:21Z

From: Steven Rostedt (VMware) <rostedt@goodmis.org>

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

Link: http://lkml.kernel.org/r/20190524111144.GI2589@hirez.programming.kicks-ass.net

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
kernel/trace/fgraph.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 30edeb6d4aa9..837daf929d2a 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -26,10 +26,9 @@
#endif

#define FGRAPH_RET_SIZE sizeof(struct ftrace_ret_stack)
-#define FGRAPH_RET_INDEX (ALIGN(FGRAPH_RET_SIZE, sizeof(long)) / sizeof(long))
+#define FGRAPH_RET_INDEX (FGRAPH_RET_SIZE / sizeof(long))
#define SHADOW_STACK_SIZE (PAGE_SIZE)
-#define SHADOW_STACK_INDEX \
- (ALIGN(SHADOW_STACK_SIZE, sizeof(long)) / sizeof(long))
+#define SHADOW_STACK_INDEX (SHADOW_STACK_SIZE / sizeof(long))
/* Leave on a buffer at the end */
#define SHADOW_STACK_MAX_INDEX (SHADOW_STACK_INDEX - FGRAPH_RET_INDEX)

@@ -91,6 +90,8 @@ 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.
@@ -325,6 +326,8 @@ ftrace_graph_get_ret_stack(struct task_struct *task, int idx)
{
int index = task->curr_ret_stack;

+ BUILD_BUG_ON(FGRAPH_RET_SIZE % sizeof(long));
+
index -= FGRAPH_RET_INDEX * (idx + 1);
if (index < 0)
return NULL;