ArmTrng.c

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#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/ArmTrngLib.h>
#include <Protocol/Rng.h>
 
#include "RngDxeInternals.h"
 
EFI_STATUS
EFIAPI
GenerateEntropy (
  IN  UINTN  Length,
  OUT UINT8  *Entropy
  )
{
  EFI_STATUS  Status;
  UINTN       CollectedEntropyBits;
  UINTN       RequiredEntropyBits;
  UINTN       EntropyBits;
  UINTN       Index;
  UINTN       MaxBits;
 
  ZeroMem (Entropy, Length);
 
  RequiredEntropyBits  = (Length << 3);
  Index                = 0;
  CollectedEntropyBits = 0;
  MaxBits              = GetArmTrngMaxSupportedEntropyBits ();
  while (CollectedEntropyBits < RequiredEntropyBits) {
    EntropyBits = MIN ((RequiredEntropyBits - CollectedEntropyBits), MaxBits);
    Status      = GetArmTrngEntropy (
                    EntropyBits,
                    (Length - Index),
                    &Entropy[Index]
                    );
    if (EFI_ERROR (Status)) {
      // Discard the collected bits.
      ZeroMem (Entropy, Length);
      return Status;
    }
 
    CollectedEntropyBits += EntropyBits;
    Index                += (EntropyBits >> 3);
  } // while
 
  return Status;
}