kcov: fix struct layout for kcov_remote_arg

Make the layout of kcov_remote_arg the same for 32-bit and 64-bit code.
This makes it more convenient to write userspace apps that can be
compiled into 32-bit or 64-bit binaries and still work with the same
64-bit kernel.

Also use proper __u32 types in uapi headers instead of unsigned ints.

Link: http://lkml.kernel.org/r/9e91020876029cfefc9211ff747685eba9536426.1575638983.git.andreyknvl@google.com
Fixes: eec028c ("kcov: remote coverage support")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Chunfeng Yun <chunfeng.yun@mediatek.com>
Cc: "Jacky . Cao @ sony . com" <Jacky.Cao@sony.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/dev-tools/kcov.rst

@@ -251,11 +251,11 @@ selectively from different subsystems.
 .. code-block:: c
 
     struct kcov_remote_arg {
-	unsigned	trace_mode;
-	unsigned	area_size;
-	unsigned	num_handles;
-	uint64_t	common_handle;
-	uint64_t	handles[0];
+	__u32		trace_mode;
+	__u32		area_size;
+	__u32		num_handles;
+	__aligned_u64	common_handle;
+	__aligned_u64	handles[0];
     };
 
     #define KCOV_INIT_TRACE			_IOR('c', 1, unsigned long)

include/uapi/linux/kcov.h

@@ -9,11 +9,11 @@
  * and the comment before kcov_remote_start() for usage details.
  */
 struct kcov_remote_arg {
-	unsigned int	trace_mode;	/* KCOV_TRACE_PC or KCOV_TRACE_CMP */
-	unsigned int	area_size;	/* Length of coverage buffer in words */
-	unsigned int	num_handles;	/* Size of handles array */
-	__u64		common_handle;
-	__u64		handles[0];
+	__u32		trace_mode;	/* KCOV_TRACE_PC or KCOV_TRACE_CMP */
+	__u32		area_size;	/* Length of coverage buffer in words */
+	__u32		num_handles;	/* Size of handles array */
+	__aligned_u64	common_handle;
+	__aligned_u64	handles[0];
 };
 
 #define KCOV_REMOTE_MAX_HANDLES		0x100