Re: [PATCH 4/5] MdeModulePkg/PartitionDxe: don't divide 64-bit values with C operators

["Bi, Dandan" <dandan.bi@intel.com>]

Hi Laszlo,

When do you plan to push this patch? IA32 build is blocked for this issue now.

Thanks,
Dandan

-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Laszlo Ersek
Sent: Sunday, September 10, 2017 8:13 AM
To: edk2-devel-01 <edk2-devel@lists.01.org>
Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; Zeng, Star <star.zeng@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
Subject: [edk2] [PATCH 4/5] MdeModulePkg/PartitionDxe: don't divide 64-bit values with C operators

In edk2, the division and shifting of 64-bit values are forbidden with C-language operators, because the compiler may generate intrinsic calls for them.

For example, clang-3.8 emits a call to "__umoddi3" for

  UDF_LOGICAL_SECTOR_SIZE % Media->BlockSize

in PartitionInstallUdfChildHandles(), if PartitionDxe is built for IA32, which then fails to link.

UDF_LOGICAL_SECTOR_SIZE has type UINT64, while EFI_BLOCK_IO_MEDIA.BlockSize has type UINT32(). Replace the % operator with a DivU64x32Remainder() call.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Paulo Alcantara <pcacjr@zytor.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 MdeModulePkg/Universal/Disk/PartitionDxe/Udf.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Universal/Disk/PartitionDxe/Udf.c b/MdeModulePkg/Universal/Disk/PartitionDxe/Udf.c
index c1d44809bfd2..c491ef25f47e 100644
--- a/MdeModulePkg/Universal/Disk/PartitionDxe/Udf.c
+++ b/MdeModulePkg/Universal/Disk/PartitionDxe/Udf.c
@@ -234,10 +234,11 @@ PartitionInstallUdfChildHandles (
   IN  EFI_BLOCK_IO_PROTOCOL        *BlockIo,
   IN  EFI_BLOCK_IO2_PROTOCOL       *BlockIo2,
   IN  EFI_DEVICE_PATH_PROTOCOL     *DevicePath
   )
 {
+  UINT32                       RemainderByMediaBlockSize;
   EFI_STATUS                   Status;
   EFI_BLOCK_IO_MEDIA           *Media;
   EFI_DEVICE_PATH_PROTOCOL     *DevicePathNode;
   EFI_GUID                     *VendorDefinedGuid;
   EFI_GUID                     UdfDevPathGuid = EFI_UDF_DEVICE_PATH_GUID;
@@ -246,11 +247,16 @@ PartitionInstallUdfChildHandles (
   Media = BlockIo->Media;
 
   //
   // Check if UDF logical block size is multiple of underlying device block size
   //
-  if ((UDF_LOGICAL_SECTOR_SIZE % Media->BlockSize) != 0 ||
+  DivU64x32Remainder (
+    UDF_LOGICAL_SECTOR_SIZE,   // Dividend
+    Media->BlockSize,          // Divisor
+    &RemainderByMediaBlockSize // Remainder
+    );
+  if (RemainderByMediaBlockSize != 0 ||
       Media->BlockSize > UDF_LOGICAL_SECTOR_SIZE) {
     return EFI_NOT_FOUND;
   }
 
   DevicePathNode = DevicePath;
--
2.14.1.3.gb7cf6e02401b


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