[PATCH v2 4/5] MdePkg/PiFirmwareFile: fix undefined behavior in FFS_FILE_SIZE

["Laszlo Ersek" <lersek@redhat.com>]

Accessing "EFI_FFS_FILE_HEADER.Size", which is of type UINT8[3], through a
(UINT32*), is undefined behavior. Fix it by accessing the array elements
individually.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=1710
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v2:
    
    - eliminate intermediate macros [Mike]

 MdePkg/Include/Pi/PiFirmwareFile.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/MdePkg/Include/Pi/PiFirmwareFile.h b/MdePkg/Include/Pi/PiFirmwareFile.h
index 05470538de42..ec7729e9c36e 100644
--- a/MdePkg/Include/Pi/PiFirmwareFile.h
+++ b/MdePkg/Include/Pi/PiFirmwareFile.h
@@ -179,8 +179,15 @@ typedef struct {
 #define IS_FFS_FILE2(FfsFileHeaderPtr) \
     (((((EFI_FFS_FILE_HEADER *) (UINTN) FfsFileHeaderPtr)->Attributes) & FFS_ATTRIB_LARGE_FILE) == FFS_ATTRIB_LARGE_FILE)
 
-#define FFS_FILE_SIZE(FfsFileHeaderPtr) \
-    ((UINT32) (*((UINT32 *) ((EFI_FFS_FILE_HEADER *) (UINTN) FfsFileHeaderPtr)->Size) & 0x00ffffff))
+///
+/// The argument passed as the FfsFileHeaderPtr parameter to the
+/// FFS_FILE_SIZE() function-like macro below must not have side effects:
+/// FfsFileHeaderPtr is evaluated multiple times.
+///
+#define FFS_FILE_SIZE(FfsFileHeaderPtr) ((UINT32) ( \
+    (((EFI_FFS_FILE_HEADER *) (UINTN) (FfsFileHeaderPtr))->Size[0]      ) | \
+    (((EFI_FFS_FILE_HEADER *) (UINTN) (FfsFileHeaderPtr))->Size[1] <<  8) | \
+    (((EFI_FFS_FILE_HEADER *) (UINTN) (FfsFileHeaderPtr))->Size[2] << 16)))
 
 #define FFS_FILE2_SIZE(FfsFileHeaderPtr) \
     ((UINT32) (((EFI_FFS_FILE_HEADER2 *) (UINTN) FfsFileHeaderPtr)->ExtendedSize))
-- 
2.19.1.3.g30247aa5d201