[PATCH v1 2/2] BaseTools: GenFw: auto-set nxcompat flag

[Joey Vagedes <joey.vagedes@gmail.com>]

Automatically set the nxcompat flag in the DLL Characteristics field of
the Optional Header of the PE32+ image. For this flag to be set
automatically, it must, the section alignment must be evenly divisible
by 4K (EFI_PAGE_SIZE) and no section must be executable and writable.

Cc: Rebecca Cran <rebecca@bsdio.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Yuwei Chen <yuwei.chen@intel.com>
Signed-off-by: Joey Vagedes <joeyvagedes@gmail.com>
---
 BaseTools/Source/C/GenFw/GenFw.c | 59 ++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/BaseTools/Source/C/GenFw/GenFw.c b/BaseTools/Source/C/GenFw/GenFw.c
index 0289c8ef8a5c..4581c4233c14 100644
--- a/BaseTools/Source/C/GenFw/GenFw.c
+++ b/BaseTools/Source/C/GenFw/GenFw.c
@@ -441,6 +441,60 @@ Returns:
   return STATUS_SUCCESS;
 }
 
+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;
+}
+
 VOID
 SetHiiResourceHeader (
   UINT8   *HiiBinData,
@@ -2458,6 +2512,11 @@ Returns:
     TEImageHeader.BaseOfCode          = Optional64->BaseOfCode;
     TEImageHeader.ImageBase           = (UINT64) (Optional64->ImageBase);
 
+    // Set NxCompat flag
+    if (IsNxCompatCompliant (PeHdr)) {
+      Optional64->DllCharacteristics |= IMAGE_DLLCHARACTERISTICS_NX_COMPAT;
+    }
+
     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;
-- 
2.41.0.windows.1