Logging

SBL provides logging for debugging purpose. It can be configured at build time for verbosity. One can control debug messages in multiple ways by modifying the following PCDs defined in BootloaderCorePkg.dsc file:

PCD Name Description
PcdFixedDebugPrintErrorLevel Build time debug message level compiled into the image
PcdDebugPropertyMask Runtime debug message level sent to the console
PcdDebugOutputDeviceMask Debug output destinations: serial console or log buffer

Commonly used definitions for these PCDs are listed here.

PcdFixedDebugPrintErrorLevel definitions:

#define DEBUG_INIT      0x00000001  // Initialization
#define DEBUG_WARN      0x00000002  // Warnings
#define DEBUG_INFO      0x00000040  // Informational debug messages
#define DEBUG_VERBOSE   0x00400000  // Detailed debug messages that may
                                    // significantly impact boot performance
#define DEBUG_ERROR     0x80000000  // Error

PcdDebugPropertyMask definitions:

#define DEBUG_PROPERTY_DEBUG_ASSERT_ENABLED       0x01
#define DEBUG_PROPERTY_DEBUG_PRINT_ENABLED        0x02
#define DEBUG_PROPERTY_DEBUG_CODE_ENABLED         0x04
#define DEBUG_PROPERTY_CLEAR_MEMORY_ENABLED       0x08
#define DEBUG_PROPERTY_ASSERT_BREAKPOINT_ENABLED  0x10
#define DEBUG_PROPERTY_ASSERT_DEADLOOP_ENABLED    0x20

PcdDebugOutputDeviceMask definitions:

#define  DEBUG_OUTPUT_DEVICE_LOG_BUFFER     BIT0
#define  DEBUG_OUTPUT_DEVICE_SERIAL_PORT    BIT1

For more details, see DebugLib.h and LoaderPlatformDataGuid.h.

An example of minimum debug output from SBL release build on QEMU emulator:

Intel Slim Bootloader
SBID: SB_QEMU
ISVN: 00001
IVER: 000.00001.11095
BOOT: BP0
MODE: 0
BoardID: 00
Memory Init
PCI Enum
ACPI Init
MP InitJump to payload

Payload startup