add a helper function to test if an object is on the stack

lib/debugobjects.c has a function to test if an object is on the stack. The block layer and ide needs it (they need to avoid DMA from/to stack buffers). This patch moves the function to include/linux/sched.h so that everyone can use it. lib/debugobjects.c uses current->stack but this patch uses a task_stack_page() accessor, which is a preferable way to access the stack. Signed-off-by: FUJITA Tomonori <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Andy Whitcroft <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Thomas Gleixner <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
rtvt123 · Jul 24, 2008 · 8b05c7e · 8b05c7e
1 parent 68ad8df
commit 8b05c7e
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Showing 2 changed files with 8 additions and 3 deletions.
diff --git a/include/linux/sched.h b/include/linux/sched.h
@@ -1983,6 +1983,13 @@ static inline unsigned long *end_of_stack(struct task_struct *p)
 
 #endif
 
+static inline int object_is_on_stack(void *obj)
+{
+	void *stack = task_stack_page(current);
+
+	return (obj >= stack) && (obj < (stack + THREAD_SIZE));
+}
+
 extern void thread_info_cache_init(void);
 
 /* set thread flags in other task's structures

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
@@ -226,15 +226,13 @@ debug_object_fixup(int (*fixup)(void *addr, enum debug_obj_state state),
 
 static void debug_object_is_on_stack(void *addr, int onstack)
 {
-	void *stack = current->stack;
 	int is_on_stack;
 	static int limit;
 
 	if (limit > 4)
 		return;
 
-	is_on_stack = (addr >= stack && addr < (stack + THREAD_SIZE));
-
+	is_on_stack = object_is_on_stack(addr);
 	if (is_on_stack == onstack)
 		return;