OvmfPkg/LoongArchVirt: Use FFS_FILE_SIZE to read FFS file size

Replace the open-coded read of the 3-byte FFS file Size[] field in
FindFfsFileAndSection() with the FFS_FILE_SIZE() macro from
Pi/PiFirmwareFile.h. The macro reads exactly the three Size[] bytes
(endianness-safe) instead of a 4-byte load that over-reads the
adjacent byte. No functional change.

Verified by building the module for LOONGARCH64 with a GCC cross
toolchain:

  build -p OvmfPkg/LoongArchVirt/LoongArchVirtQemu.dsc -a LOONGARCH64 \
        -t GCC -b DEBUG -m OvmfPkg/LoongArchVirt/Sec/SecMain.inf

SecMain.c compiles and links into SecMain.efi.

Generated with the following Coccinelle semantic patch:

```smpl
@@
EFI_FFS_FILE_HEADER *E;
typedef UINT32;
@@
(
- *(UINT32 *)(E->Size) & 0x00FFFFFF
+ FFS_FILE_SIZE (E)
|
- *(UINT32 *)E->Size & 0x00FFFFFF
+ FFS_FILE_SIZE (E)
)
```

Signed-off-by: Mingjie Shen <shen497@purdue.edu>

1 files changed, 1 insertions, 1 deletions

diff --git a/OvmfPkg/LoongArchVirt/Sec/SecMain.c b/OvmfPkg/LoongArchVirt/Sec/SecMain.c
index 6f541b1b89..10df18f3fd 100644
--- a/OvmfPkg/LoongArchVirt/Sec/SecMain.c
+++ b/OvmfPkg/LoongArchVirt/Sec/SecMain.c
@@ -207,7 +207,7 @@ FindFfsFileAndSection (
     }

 

     File = (EFI_FFS_FILE_HEADER *)(UINTN)CurrentAddress;

-    Size = *(UINT32 *)File->Size & 0xffffff;

+    Size = FFS_FILE_SIZE (File);

     if (Size < (sizeof (*File) + sizeof (EFI_COMMON_SECTION_HEADER))) {

       return EFI_VOLUME_CORRUPTED;

     }