GenFw: auto set nxcompat flag (#456)

## Description

GenFw will now automatically set the nxcompat if the PE file meets the
requirements. Those requirements are:

1. A 64 bit PE file
2. Has 4K alignment or is evenly divisible by 4K
3. No section has both Write and Execute

This fixup takes place inside the main function, scoped to only when the
PE's OptionalHeader's Magic is EFI_IMAGE_NT_OPTIONAL_HDR64_MAGIC

- [x] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [x] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

1. Verified proper build on Windows and Fedora
2. Verified proper build on Windows with /NXCOMPAT and SUBSYSTEM:CONSOLE
removed from VS2022 X64 DLINK_FLAGS
1. Verified nxcompat flags were properly set on binaries built with GCC5
and VS2022
2. Verified MemoryProtectionTestApp.efi passes all
`Security.NxProtection` tests on QemuQ35 and Sbsa VS2022 / GCC5
3. Verified MemoryAttributeProtocolFuncTestApp.efi,
DxePagingAuditTestApp.efi pass on QemuQ35 VS2022 / GCC5

## Integration Instructions

N/A

---------

Signed-off-by: Joey Vagedes <joey.vagedes@gmail.com>
Co-authored-by: Michael Kubacki <michael.kubacki@microsoft.com>

BaseTools/Source/C/GenFw/GenFw.c

@@ -443,6 +443,62 @@ Routine Description:
   return STATUS_SUCCESS;
 }
 
+// MU_CHANGE begin
+STATIC
+BOOLEAN
+IsNxCompatCompliant (
+  EFI_IMAGE_OPTIONAL_HEADER_UNION  *PeHdr
+  )
+/*++
+
+Routine Description:
+
+  Checks if the Pe image is nxcompat. i.e. PE is 64bit, section alignment is
+  evenly divisible by 4k, and no section is writable and executable.
+
+Arguments:
+
+  PeHdr      The Pe header
+
+Returns:
+
+  TRUE       The PE is nx compat compliant
+  FALSE      The PE is not nx compat compliant
+--*/
+{
+  EFI_IMAGE_SECTION_HEADER     *SectionHeader;
+  UINT32                       Index;
+  UINT32                       Mask;
+
+  // Must have an optional header to perform verification
+  if (PeHdr->Pe32.FileHeader.SizeOfOptionalHeader == 0) {
+    return FALSE;
+  }
+
+  // Verify PE is 64 bit
+  if (!(PeHdr->Pe32.OptionalHeader.Magic == EFI_IMAGE_NT_OPTIONAL_HDR64_MAGIC)) {
+    return FALSE;
+  }
+
+  // Verify Section Alignment is divisible by 4K
+  if (!((PeHdr->Pe32Plus.OptionalHeader.SectionAlignment % EFI_PAGE_SIZE) == 0)) {
+    return FALSE;
+  }
+
+  // Verify sections are not Write & Execute
+  Mask = EFI_IMAGE_SCN_MEM_EXECUTE | EFI_IMAGE_SCN_MEM_WRITE;
+  SectionHeader = (EFI_IMAGE_SECTION_HEADER *) ((UINT8 *) &(PeHdr->Pe32Plus.OptionalHeader) + PeHdr->Pe32Plus.FileHeader.SizeOfOptionalHeader);
+  for (Index = 0; Index < PeHdr->Pe32Plus.FileHeader.NumberOfSections; Index ++, SectionHeader ++) {
+    if ((SectionHeader->Characteristics & Mask) == Mask) {
+      return FALSE;
+    }  
+  }
+
+  // Passed all requirements, return TRUE
+  return TRUE;
+}
+// MU_CHANGE end
+
 VOID
 SetHiiResourceHeader (
   UINT8   *HiiBinData,
@@ -2466,6 +2522,13 @@ Routine Description:
     TEImageHeader.BaseOfCode          = Optional64->BaseOfCode;
     TEImageHeader.ImageBase           = (UINT64) (Optional64->ImageBase);
 
+    // MU_CHANGE begin
+    // Set NxCompat flag
+    if (IsNxCompatCompliant (PeHdr)) {
+      Optional64->DllCharacteristics |= IMAGE_DLLCHARACTERISTICS_NX_COMPAT;
+    }
+    // MU_CHANGE end
+
     if (Optional64->NumberOfRvaAndSizes > EFI_IMAGE_DIRECTORY_ENTRY_BASERELOC) {
       TEImageHeader.DataDirectory[EFI_TE_IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress = Optional64->DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress;
       TEImageHeader.DataDirectory[EFI_TE_IMAGE_DIRECTORY_ENTRY_BASERELOC].Size = Optional64->DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_BASERELOC].Size;

BaseTools/Source/C/Include/IndustryStandard/PeImage.h

@@ -286,6 +286,23 @@ typedef struct {
 #define EFI_IMAGE_SUBSYSTEM_OS2_CUI     5
 #define EFI_IMAGE_SUBSYSTEM_POSIX_CUI   7
 
+// MU_CHANGE begin
+//
+// DLL Characteristics
+//
+#define IMAGE_DLLCHARACTERISTICS_HIGH_ENTROPY_VA       0x0020
+#define IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE          0x0040
+#define IMAGE_DLLCHARACTERISTICS_FORCE_INTEGRITY       0x0080
+#define IMAGE_DLLCHARACTERISTICS_NX_COMPAT             0x0100
+#define IMAGE_DLLCHARACTERISTICS_NO_ISOLATION          0x0200
+#define IMAGE_DLLCHARACTERISTICS_NO_SEH                0x0400
+#define IMAGE_DLLCHARACTERISTICS_NO_BIND               0x0800
+#define IMAGE_DLLCHARACTERISTICS_APPCONTAINER          0x1000
+#define IMAGE_DLLCHARACTERISTICS_WDM_DRIVER            0x2000
+#define IMAGE_DLLCHARACTERISTICS_GUARD_CF              0x4000
+#define IMAGE_DLLCHARACTERISTICS_TERMINAL_SERVER_AWARE 0x8000
+// MU_CHANGE end
+
 //
 // Directory Entries
 //