BaseTools: Fix FMMT FvHandler Padding operation issue

When using the FMMT FvHandler function, new padding size
should be calculated correctly comparing with origin ffs
and new ffs, else it will cause the binary size changes.
This patch is used to fix the bug.

Signed-off-by: Yuwei Chen <yuwei.chen@intel.com>

Author: YuweiChen1110

BaseTools/Source/Python/FMMT/core/FvHandler.py

@@ -237,11 +237,20 @@ def CompressSectionData(self, TargetTree, pos: int, GuidTool=None) -> None:
                 Size_delta = len(CompressedData) - len(TargetTree.Data.OriData)
                 ChangeSize(TargetTree, -Size_delta)
                 if TargetTree.NextRel:
+                    Original_Pad_Size = len(TargetTree.Data.PadData)
                     TargetTree.Data.PadData = b'\x00' * New_Pad_Size
-                    self.Remain_New_Free_Space = len(TargetTree.Data.OriData) + len(TargetTree.Data.PadData) - len(CompressedData) - New_Pad_Size
+                    self.Remain_New_Free_Space = (
+                        len(TargetTree.Data.OriData) +
+                        Original_Pad_Size -
+                        len(CompressedData) -
+                        New_Pad_Size
+                    )
                 else:
                     TargetTree.Data.PadData = b''
-                    self.Remain_New_Free_Space = len(TargetTree.Data.OriData) - len(CompressedData)
+                    self.Remain_New_Free_Space = (
+                        len(TargetTree.Data.OriData) -
+                        len(CompressedData)
+                    )
                 TargetTree.Data.OriData = CompressedData
             elif len(CompressedData) == len(TargetTree.Data.OriData):
                 TargetTree.Data.OriData = CompressedData
@@ -347,15 +356,24 @@ def ModifyTest(self, ParTree, Needed_Space: int) -> None:
                     ModifySectionType(ParTree)
                     Needed_Space += ParTree.Data.HeaderLength - OriHeaderLen
                     # Update needed space with Delta_Pad_Size
+                    Original_Pad_Size = len(ParTree.Data.PadData)
                     if ParTree.NextRel:
                         New_Pad_Size = GetPadSize(ParTree.Data.Size, SECTION_COMMON_ALIGNMENT)
-                        Delta_Pad_Size = New_Pad_Size - len(ParTree.Data.PadData)
+                        Delta_Pad_Size = New_Pad_Size - Original_Pad_Size
                         ParTree.Data.PadData = b'\x00' * New_Pad_Size
                         Needed_Space += Delta_Pad_Size
                     else:
                         ParTree.Data.PadData = b''
                     if Needed_Space < 0:
-                        self.Remain_New_Free_Space = len(ParTree.Data.OriData) - len(CompressedData)
+                        if ParTree.NextRel:
+                            self.Remain_New_Free_Space = (
+                                len(ParTree.Data.OriData) + Original_Pad_Size -
+                                len(CompressedData) - New_Pad_Size
+                            )
+                        else:
+                            self.Remain_New_Free_Space = (
+                                len(ParTree.Data.OriData) - len(CompressedData)
+                            )
                 # If current section is not guided section
                 elif Needed_Space:
                     ChangeSize(ParTree, -Needed_Space)