PeCoffLoaderEx.c

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#include "BasePeCoffLibInternals.h"
#include <Library/BaseLib.h>
 
UINT16
ThumbMovtImmediateAddress (
  IN UINT16  *Instruction
  )
{
  UINT32  Movt;
  UINT16  Address;
 
  // Thumb2 is two 16-bit instructions working together. Not a single 32-bit instruction
  // Example MOVT R0, #0 is 0x0000f2c0 or 0xf2c0 0x0000
  Movt = (*Instruction << 16) | (*(Instruction + 1));
 
  // imm16 = imm4:i:imm3:imm8
  //         imm4 -> Bit19:Bit16
  //         i    -> Bit26
  //         imm3 -> Bit14:Bit12
  //         imm8 -> Bit7:Bit0
  Address  = (UINT16)(Movt & 0x000000ff);         // imm8
  Address |= (UINT16)((Movt >> 4) &  0x0000f700); // imm4 imm3
  Address |= (((Movt & BIT26) != 0) ? BIT11 : 0); // i
  return Address;
}
 
VOID
ThumbMovtImmediatePatch (
  IN OUT UINT16  *Instruction,
  IN     UINT16  Address
  )
{
  UINT16  Patch;
 
  // First 16-bit chunk of instruciton
  Patch  = ((Address >> 12) & 0x000f);             // imm4
  Patch |= (((Address & BIT11) != 0) ? BIT10 : 0); // i
  // Mask out instruction bits and or in address
  *(Instruction) = (*Instruction & ~0x040f) | Patch;
 
  // Second 16-bit chunk of instruction
  Patch  =  Address & 0x000000ff;          // imm8
  Patch |=  ((Address << 4) & 0x00007000); // imm3
  // Mask out instruction bits and or in address
  Instruction++;
  *Instruction = (*Instruction & ~0x70ff) | Patch;
}
 
UINT32
ThumbMovwMovtImmediateAddress (
  IN UINT16  *Instructions
  )
{
  UINT16  *Word;
  UINT16  *Top;
 
  Word = Instructions;  // MOVW
  Top  = Word + 2;      // MOVT
 
  return (ThumbMovtImmediateAddress (Top) << 16) + ThumbMovtImmediateAddress (Word);
}
 
VOID
ThumbMovwMovtImmediatePatch (
  IN OUT UINT16  *Instructions,
  IN     UINT32  Address
  )
{
  UINT16  *Word;
  UINT16  *Top;
 
  Word = Instructions;  // MOVW
  Top  = Word + 2;      // MOVT
 
  ThumbMovtImmediatePatch (Word, (UINT16)(Address & 0xffff));
  ThumbMovtImmediatePatch (Top, (UINT16)(Address >> 16));
}
 
RETURN_STATUS
PeCoffLoaderRelocateImageEx (
  IN UINT16     *Reloc,
  IN OUT CHAR8  *Fixup,
  IN OUT CHAR8  **FixupData,
  IN UINT64     Adjust
  )
{
  UINT16  *Fixup16;
  UINT32  FixupVal;
 
  Fixup16 = (UINT16 *)Fixup;
 
  switch ((*Reloc) >> 12) {
    case EFI_IMAGE_REL_BASED_ARM_MOV32T:
      FixupVal = ThumbMovwMovtImmediateAddress (Fixup16) + (UINT32)Adjust;
      ThumbMovwMovtImmediatePatch (Fixup16, FixupVal);
 
      if (*FixupData != NULL) {
        *FixupData = ALIGN_POINTER (*FixupData, sizeof (UINT64));
        // Fixup16 is not aligned so we must copy it. Thumb instructions are streams of 16 bytes.
        CopyMem (*FixupData, Fixup16, sizeof (UINT64));
        *FixupData = *FixupData + sizeof (UINT64);
      }
 
      break;
 
    case EFI_IMAGE_REL_BASED_ARM_MOV32A:
      ASSERT (FALSE);
    // break omitted - ARM instruction encoding not implemented
    default:
      return RETURN_UNSUPPORTED;
  }
 
  return RETURN_SUCCESS;
}
 
BOOLEAN
PeCoffLoaderImageFormatSupported (
  IN  UINT16  Machine
  )
{
  if ((Machine == IMAGE_FILE_MACHINE_ARMTHUMB_MIXED) || (Machine ==  IMAGE_FILE_MACHINE_EBC)) {
    return TRUE;
  }
 
  return FALSE;
}
 
RETURN_STATUS
PeHotRelocateImageEx (
  IN UINT16     *Reloc,
  IN OUT CHAR8  *Fixup,
  IN OUT CHAR8  **FixupData,
  IN UINT64     Adjust
  )
{
  UINT16  *Fixup16;
  UINT32  FixupVal;
 
  Fixup16 = (UINT16 *)Fixup;
 
  switch ((*Reloc) >> 12) {
    case EFI_IMAGE_REL_BASED_ARM_MOV32T:
      *FixupData = ALIGN_POINTER (*FixupData, sizeof (UINT64));
      if (*(UINT64 *)(*FixupData) == ReadUnaligned64 ((UINT64 *)Fixup16)) {
        FixupVal = ThumbMovwMovtImmediateAddress (Fixup16) + (UINT32)Adjust;
        ThumbMovwMovtImmediatePatch (Fixup16, FixupVal);
      }
 
      *FixupData = *FixupData + sizeof (UINT64);
      break;
 
    case EFI_IMAGE_REL_BASED_ARM_MOV32A:
      ASSERT (FALSE);
    // break omitted - ARM instruction encoding not implemented
    default:
      DEBUG ((DEBUG_ERROR, "PeHotRelocateEx:unknown fixed type\n"));
      return RETURN_UNSUPPORTED;
  }
 
  return RETURN_SUCCESS;
}