X86PatchInstruction.c

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#include "BaseLibInternals.h"
 
VOID
EFIAPI
PatchInstructionX86 (
  OUT X86_ASSEMBLY_PATCH_LABEL  *InstructionEnd,
  IN  UINT64                    PatchValue,
  IN  UINTN                     ValueSize
  )
{
  //
  // The equality ((UINTN)InstructionEnd == ValueSize) would assume a zero-size
  // instruction at address 0; forbid it.
  //
  ASSERT ((UINTN)InstructionEnd > ValueSize);
 
  switch (ValueSize) {
    case 1:
      ASSERT (PatchValue <= MAX_UINT8);
      *((UINT8 *)(UINTN)InstructionEnd - 1) = (UINT8)PatchValue;
      break;
 
    case 2:
      ASSERT (PatchValue <= MAX_UINT16);
      WriteUnaligned16 ((UINT16 *)(UINTN)InstructionEnd - 1, (UINT16)PatchValue);
      break;
 
    case 4:
      ASSERT (PatchValue <= MAX_UINT32);
      WriteUnaligned32 ((UINT32 *)(UINTN)InstructionEnd - 1, (UINT32)PatchValue);
      break;
 
    case 8:
      WriteUnaligned64 ((UINT64 *)(UINTN)InstructionEnd - 1, PatchValue);
      break;
 
    default:
      ASSERT (FALSE);
  }
}