ArmTrngLib.c

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#include <Base.h>
#include <Library/ArmLib.h>
#include <Library/ArmMonitorLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
 
#include "ArmTrngDefs.h"
 
STATIC
RETURN_STATUS
TrngStatusToReturnStatus (
  IN  INT32  TrngStatus
  )
{
  switch (TrngStatus) {
    case TRNG_STATUS_NOT_SUPPORTED:
      return RETURN_UNSUPPORTED;
 
    case TRNG_STATUS_INVALID_PARAMETER:
      return RETURN_INVALID_PARAMETER;
 
    case TRNG_STATUS_NO_ENTROPY:
      return RETURN_NOT_READY;
 
    case TRNG_STATUS_SUCCESS:
      return RETURN_SUCCESS;
 
    default:
      if (TrngStatus < 0) {
        return RETURN_UNSUPPORTED;
      }
 
      return RETURN_SUCCESS;
  }
}
 
RETURN_STATUS
EFIAPI
GetArmTrngVersion (
  OUT UINT16  *MajorRevision,
  OUT UINT16  *MinorRevision
  )
{
  RETURN_STATUS     Status;
  ARM_MONITOR_ARGS  Parameters;
  INT32             Revision;
 
  if ((MajorRevision == NULL) || (MinorRevision == NULL)) {
    return RETURN_INVALID_PARAMETER;
  }
 
  ZeroMem (&Parameters, sizeof (Parameters));
 
  Parameters.Arg0 = ARM_SMC_ID_TRNG_VERSION;
  ArmMonitorCall (&Parameters);
 
  Revision = (INT32)Parameters.Arg0;
  Status   = TrngStatusToReturnStatus (Revision);
  if (RETURN_ERROR (Status)) {
    return Status;
  }
 
  *MinorRevision = (Revision & TRNG_REV_MINOR_MASK);
  *MajorRevision = ((Revision >> TRNG_REV_MAJOR_SHIFT) & TRNG_REV_MAJOR_MASK);
  return RETURN_SUCCESS;
}
 
STATIC
RETURN_STATUS
EFIAPI
GetArmTrngFeatures (
  IN  CONST UINT32  FunctionId,
  OUT       UINT32  *Capability      OPTIONAL
  )
{
  ARM_MONITOR_ARGS  Parameters;
  RETURN_STATUS     Status;
 
  ZeroMem (&Parameters, sizeof (Parameters));
 
  Parameters.Arg0 = ARM_SMC_ID_TRNG_FEATURES;
  Parameters.Arg1 = FunctionId;
  ArmMonitorCall (&Parameters);
 
  Status = TrngStatusToReturnStatus (Parameters.Arg0);
  if (RETURN_ERROR (Status)) {
    return Status;
  }
 
  if (Capability != NULL) {
    *Capability = (UINT32)Parameters.Arg0;
  }
 
  return RETURN_SUCCESS;
}
 
RETURN_STATUS
EFIAPI
GetArmTrngUuid (
  OUT GUID  *Guid
  )
{
  ARM_MONITOR_ARGS  Parameters;
 
  if (Guid == NULL) {
    return RETURN_INVALID_PARAMETER;
  }
 
  ZeroMem (&Parameters, sizeof (Parameters));
 
  Parameters.Arg0 = ARM_SMC_ID_TRNG_GET_UUID;
  ArmMonitorCall (&Parameters);
 
  // Only invalid value is TRNG_STATUS_NOT_SUPPORTED (-1).
  if ((INT32)Parameters.Arg0 == TRNG_STATUS_NOT_SUPPORTED) {
    return TrngStatusToReturnStatus ((INT32)Parameters.Arg0);
  }
 
  Guid->Data1 = (Parameters.Arg0 & MAX_UINT32);
  Guid->Data2 = (Parameters.Arg1 & MAX_UINT16);
  Guid->Data3 = ((Parameters.Arg1 >> 16) & MAX_UINT16);
 
  Guid->Data4[0] = (Parameters.Arg2 & MAX_UINT8);
  Guid->Data4[1] = ((Parameters.Arg2 >> 8) & MAX_UINT8);
  Guid->Data4[2] = ((Parameters.Arg2 >> 16) & MAX_UINT8);
  Guid->Data4[3] = ((Parameters.Arg2 >> 24) & MAX_UINT8);
 
  Guid->Data4[4] = (Parameters.Arg3 & MAX_UINT8);
  Guid->Data4[5] = ((Parameters.Arg3 >> 8) & MAX_UINT8);
  Guid->Data4[6] = ((Parameters.Arg3 >> 16) & MAX_UINT8);
  Guid->Data4[7] = ((Parameters.Arg3 >> 24) & MAX_UINT8);
 
  DEBUG ((DEBUG_INFO, "FW-TRNG: UUID %g\n", Guid));
 
  return RETURN_SUCCESS;
}
 
UINTN
EFIAPI
GetArmTrngMaxSupportedEntropyBits (
  VOID
  )
{
  return MAX_ENTROPY_BITS;
}
 
RETURN_STATUS
EFIAPI
GetArmTrngEntropy (
  IN  UINTN  EntropyBits,
  IN  UINTN  BufferSize,
  OUT UINT8  *Buffer
  )
{
  RETURN_STATUS     Status;
  ARM_MONITOR_ARGS  Parameters;
  UINTN             EntropyBytes;
  UINTN             LastValidBits;
  UINTN             BytesToClear;
  UINTN             EntropyData[3];
 
  if ((EntropyBits == 0)                ||
      (EntropyBits > MAX_ENTROPY_BITS)  ||
      (Buffer == NULL))
  {
    return RETURN_INVALID_PARAMETER;
  }
 
  EntropyBytes = (EntropyBits + 7) >> 3;
  if (EntropyBytes > BufferSize) {
    return RETURN_BAD_BUFFER_SIZE;
  }
 
  ZeroMem (Buffer, BufferSize);
  ZeroMem (&Parameters, sizeof (Parameters));
 
  Parameters.Arg0 = ARM_SMC_ID_TRNG_RND;
  Parameters.Arg1 = EntropyBits;
  ArmMonitorCall (&Parameters);
 
  Status = TrngStatusToReturnStatus ((INT32)Parameters.Arg0);
  if (RETURN_ERROR (Status)) {
    return Status;
  }
 
  // The entropy data is returned in the Parameters.Arg<3..1>
  // With the lower order bytes in Parameters.Arg3 and the higher
  // order bytes being stored in Parameters.Arg1.
  EntropyData[0] = Parameters.Arg3;
  EntropyData[1] = Parameters.Arg2;
  EntropyData[2] = Parameters.Arg1;
 
  CopyMem (Buffer, EntropyData, EntropyBytes);
 
  // Mask off any unused top bytes, in accordance with specification.
  BytesToClear = BufferSize - EntropyBytes;
  if (BytesToClear != 0) {
    ZeroMem (&Buffer[EntropyBytes], BytesToClear);
  }
 
  // Clear the unused MSB bits of the last byte.
  LastValidBits = EntropyBits & 0x7;
  if (LastValidBits != 0) {
    Buffer[EntropyBytes - 1] &= (0xFF >> (8 - LastValidBits));
  }
 
  return Status;
}
 
RETURN_STATUS
EFIAPI
ArmTrngLibConstructor (
  VOID
  )
{
  ARM_MONITOR_ARGS  Parameters;
  RETURN_STATUS     Status;
  UINT16            MajorRev;
  UINT16            MinorRev;
  GUID              Guid;
 
  ZeroMem (&Parameters, sizeof (Parameters));
 
  Parameters.Arg0 = SMCCC_VERSION;
  ArmMonitorCall (&Parameters);
  Status = TrngStatusToReturnStatus ((INT32)Parameters.Arg0);
  if (RETURN_ERROR (Status)) {
    goto ErrorHandler;
  }
 
  // Cf [1] s2.1.3 'Caller responsibilities',
  // SMCCC version must be greater or equal than 1.1
  if ((INT32)Parameters.Arg0 < 0x10001) {
    goto ErrorHandler;
  }
 
  Status = GetArmTrngVersion (&MajorRev, &MinorRev);
  if (RETURN_ERROR (Status)) {
    goto ErrorHandler;
  }
 
  // Check that the required features are present.
  Status = GetArmTrngFeatures (ARM_SMC_ID_TRNG_RND, NULL);
  if (RETURN_ERROR (Status)) {
    goto ErrorHandler;
  }
 
  // Check if TRNG UUID is supported and if so trace the GUID.
  Status = GetArmTrngFeatures (ARM_SMC_ID_TRNG_GET_UUID, NULL);
  if (RETURN_ERROR (Status)) {
    goto ErrorHandler;
  }
 
  DEBUG_CODE_BEGIN ();
 
  Status = GetArmTrngUuid (&Guid);
  if (RETURN_ERROR (Status)) {
    goto ErrorHandler;
  }
 
  DEBUG ((
    DEBUG_INFO,
    "FW-TRNG: Version %d.%d, GUID {%g}\n",
    MajorRev,
    MinorRev,
    &Guid
    ));
 
  DEBUG_CODE_END ();
 
  return RETURN_SUCCESS;
 
ErrorHandler:
  DEBUG ((DEBUG_ERROR, "ArmTrngLib could not be correctly initialized.\n"));
  return RETURN_SUCCESS;
}