linch0520的部落格

EFI 架構中有許多Variable，為了可以讓像是AP, Driver 之間可以傳遞資料

GetNextVariableName()
  Summary
  GetNextVariableName() is called multiple times to retrieve the VariableName and
  VendorGuid of all variables

Prototype :
EFI_STATUS
GetNextVariableName (
  IN OUT UINTN    *VariableNameSize,
  IN OUT CHAR16    *VariableName,
  IN OUT EFI_GUID    *VendorGuid
  );

GetVariable()
  Summary
  Returns the value of a variable.

Prototype :
EFI_STATUS
GetVariable (
  IN CHAR16      *VariableName,
  IN EFI_GUID    *VendorGuid,
OUT UINT32     *Attributes OPTIONAL,
  IN OUT UINTN    *DataSize,
  OUT VOID      *Data
  );

SetVariable()

Summary
  Sets the value of a variable.  
  Prototype
 
EFI_STATUS
SetVariable (
  IN CHAR16      *VariableName,
  IN EFI_GUID    *VendorGuid,
  IN UINT32      Attributes,
  IN UINTN      DataSize,
  IN VOID      *Data
  );

Setting a data variable with no access, or zero DataSize attributes specified causes it to be
deleted.

//*******************************************************
// Variable Attributes
//*******************************************************
#define EFI_VARIABLE_NON_VOLATILE              0x0000000000000001
#define EFI_VARIABLE_BOOTSERVICE_ACCESS  0x0000000000000002
#define EFI_VARIABLE_RUNTIME_ACCESS          0x0000000000000004

Variable 的應用 : 像是boot order 就會以NV 的方式儲存

NV Variable  儲存在BIOS ROM，BS, RT 存在RAM

有NV屬性的BS, RT 會同時儲存在RAM、ROM 當中