EmulatorPkg: spurious failure in WriteBlocks on X64

[idigdoug]

Description

WinNtBlockIoWriteBlocks can spuriously fail on X64. This occurs because &BytesWritten is a UINTN* (i.e. UINT64*) but is cast to LPDWORD (i.e. UINT32*). Only the low 32 bits are initialized by WriteFile, so the high 32 bits are uninitialized. This means we will spuriously fail the BytesWritten != BufferSize test.

This doesn't occur on X86-32 since UINTN is the same as DWORD in that case.

Fix is to declare BytesWritten as DWORD to match the type expected by WriteFile. This also makes the cast unnecessary.

• Breaking change?
  • Breaking change - Does this PR cause a break in build or boot behavior?
  • Examples: Does it add a new library class or move a module to a different repo.
• Impacts security?
  • Security - Does this PR have a direct security impact?
  • Examples: Crypto algorithm change or buffer overflow fix.
• Includes tests?
  • Tests - Does this PR include any explicit test code?
  • Examples: Unit tests or integration tests.

How This Was Tested

• Observed spurious failures in WriteBlocks.
• Applied fix.
• WriteBlocks now works as expected.

Integration Instructions

N/A