[PATCH v4 1/3] usercopy: create enum stack_type

[James Morse]

From: Sahara <keun-o.park at darkmatter.ae>

This patch creates enum stack_type which is only used in usercopy.c
for now. This enum type can be used for x86 and other architecture's
thread_info.h, which may have arch_within_stack_frames().

Signed-off-by: Sahara <keun-o.park at darkmatter.ae>
Signed-off-by: James Morse <james.morse at arm.com>
Reviewed-by: Kees Cook <keescook at chromium.org>
Acked-by: Kees Cook <keescook at chromium.org>
---
 arch/x86/include/asm/thread_info.h | 19 ++++++++++---------
 include/linux/thread_info.h        | 13 ++++++++++---
 mm/usercopy.c                      |  8 +-------
 3 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index ad6f5eb07a95..7af4b8b23b8b 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -168,13 +168,13 @@ static inline unsigned long current_stack_pointer(void)
  * entirely contained by a single stack frame.
  *
  * Returns:
- *		 1 if within a frame
- *		-1 if placed across a frame boundary (or outside stack)
- *		 0 unable to determine (no frame pointers, etc)
+ *	GOOD_FRAME	if within a frame
+ *	BAD_STACK	if placed across a frame boundary (or outside stack)
+ *	NOT_STACK	unable to determine (no frame pointers, etc)
  */
-static inline int arch_within_stack_frames(const void * const stack,
-					   const void * const stackend,
-					   const void *obj, unsigned long len)
+static inline enum stack_type arch_within_stack_frames(const void * const stack,
+					const void * const stackend,
+					const void *obj, unsigned long len)
 {
 #if defined(CONFIG_FRAME_POINTER)
 	const void *frame = NULL;
@@ -197,13 +197,14 @@ static inline int arch_within_stack_frames(const void * const stack,
 		 * the copy as invalid.
 		 */
 		if (obj + len <= frame)
-			return obj >= oldframe + 2 * sizeof(void *) ? 1 : -1;
+			return obj >= oldframe + 2 * sizeof(void *) ?
+				GOOD_FRAME : BAD_STACK;
 		oldframe = frame;
 		frame = *(const void * const *)frame;
 	}
-	return -1;
+	return BAD_STACK;
 #else
-	return 0;
+	return NOT_STACK;
 #endif
 }
 
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 58373875e8ee..a38b3be347df 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -22,6 +22,13 @@
 #endif
 
 #include <linux/bitops.h>
+
+enum stack_type {
+	BAD_STACK = -1,
+	NOT_STACK = 0,
+	GOOD_FRAME,
+	GOOD_STACK,
+};
 #include <asm/thread_info.h>
 
 #ifdef __KERNEL__
@@ -77,9 +84,9 @@ static inline int test_ti_thread_flag(struct thread_info *ti, int flag)
 #define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED)
 
 #ifndef CONFIG_HAVE_ARCH_WITHIN_STACK_FRAMES
-static inline int arch_within_stack_frames(const void * const stack,
-					   const void * const stackend,
-					   const void *obj, unsigned long len)
+static inline enum stack_type arch_within_stack_frames(const void * const stack,
+					const void * const stackend,
+					const void *obj, unsigned long len)
 {
 	return 0;
 }
diff --git a/mm/usercopy.c b/mm/usercopy.c
index 3c8da0af9695..3531ae735d87 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -16,15 +16,9 @@
 
 #include <linux/mm.h>
 #include <linux/slab.h>
+#include <linux/thread_info.h>
 #include <asm/sections.h>
 
-enum {
-	BAD_STACK = -1,
-	NOT_STACK = 0,
-	GOOD_FRAME,
-	GOOD_STACK,
-};
-
 /*
  * Checks if a given pointer and length is contained by the current
  * stack frame (if possible).
-- 
2.10.1