Update Mass Storage bootloader so that it can support devices with only 4KB bootloader sections by creating a special AUX section before the real bootloader section to store part of the bootloader code.

12 files changed, 136 insertions, 109 deletions

diff --git a/Bootloaders/MassStorage/BootloaderAPITable.S b/Bootloaders/MassStorage/BootloaderAPITable.S
index 2aded7421..2d7610b58 100644
--- a/Bootloaders/MassStorage/BootloaderAPITable.S
+++ b/Bootloaders/MassStorage/BootloaderAPITable.S
@@ -28,6 +28,19 @@
   this software.

 */

 

+#if AUX_BOOT_SECTION_SIZE > 0

+

+#warning Using a AUX bootloader section in addition to the defined bootloader space (see documentation).

+

+; Trampoline to jump over the AUX bootloader section to the start of the bootloader,

+; on devices where an AUX bootloader section is used.

+.section .boot_aux_trampoline, "ax"

+.global Boot_AUX_Trampoline

+Boot_AUX_Trampoline:

+	jmp BOOT_START_ADDR

+

+#endif

+

 ; Trampolines to actual API implementations if the target address is outside the

 ; range of a rjmp instruction (can happen with large bootloader sections)

 .section .apitable_trampolines, "ax"

diff --git a/Bootloaders/MassStorage/BootloaderMassStorage.c b/Bootloaders/MassStorage/BootloaderMassStorage.c
index 7adeaced7..a5e953a5b 100644
--- a/Bootloaders/MassStorage/BootloaderMassStorage.c
+++ b/Bootloaders/MassStorage/BootloaderMassStorage.c
@@ -61,6 +61,25 @@ USB_ClassInfo_MS_Device_t Disk_MS_Interface =
 	};
 
 
+void Application_Jump_Check(void)
+{
+	bool JumpToApplication = false;
+
+	#if (BOARD == BOARD_LEONARDO)
+		/* Enable pull-up on the IO13 pin so we can use it to select the mode */
+		PORTC |=  (1 << 7);
+		Delay_MS(10);
+		JumpToApplication |= ((PINC & (1 << 7)) != 0);
+		PORTC &= ~(1 << 7);
+	#endif
+
+	if (JumpToApplication)
+	{
+		// cppcheck-suppress constStatement
+		((void (*)(void))0x0000)();
+	}
+}
+
 /** Main program entry point. This routine configures the hardware required by the application, then
  *  enters a loop to run the application tasks in sequence.
  */
@@ -85,9 +104,6 @@ static void SetupHardware(void)
 	MCUSR &= ~(1 << WDRF);
 	wdt_disable();
 
-	/* Disable clock division */
-	clock_prescale_set(clock_div_1);
-
 	/* Relocate the interrupt vector table to the bootloader section */
 	MCUCR = (1 << IVCE);
 	MCUCR = (1 << IVSEL);
diff --git a/Bootloaders/MassStorage/BootloaderMassStorage.h b/Bootloaders/MassStorage/BootloaderMassStorage.h
index b12cbafe5..dd67381f7 100644
--- a/Bootloaders/MassStorage/BootloaderMassStorage.h
+++ b/Bootloaders/MassStorage/BootloaderMassStorage.h
@@ -39,7 +39,6 @@
 	/* Includes: */
 		#include <avr/io.h>
 		#include <avr/wdt.h>
-		#include <avr/power.h>
 		#include <avr/interrupt.h>
 		#include <string.h>
 
@@ -67,14 +66,18 @@
 		#define LEDMASK_USB_BUSY          LEDS_LED2
 
 	/* Function Prototypes: */
-		static void SetupHardware(void);
+		int main(void) AUX_BOOT_SECTION;
 
-		void EVENT_USB_Device_Connect(void);
-		void EVENT_USB_Device_Disconnect(void);
-		void EVENT_USB_Device_ConfigurationChanged(void);
-		void EVENT_USB_Device_ControlRequest(void);
+		static void SetupHardware(void) AUX_BOOT_SECTION;
 
-		bool CALLBACK_MS_Device_SCSICommandReceived(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo);
+		void Application_Jump_Check(void) ATTR_INIT_SECTION(3);
+
+		void EVENT_USB_Device_Connect(void) AUX_BOOT_SECTION;
+		void EVENT_USB_Device_Disconnect(void) AUX_BOOT_SECTION;
+		void EVENT_USB_Device_ConfigurationChanged(void) AUX_BOOT_SECTION;
+		void EVENT_USB_Device_ControlRequest(void) AUX_BOOT_SECTION;
+
+		bool CALLBACK_MS_Device_SCSICommandReceived(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo) AUX_BOOT_SECTION;
 
 #endif
 
diff --git a/Bootloaders/MassStorage/BootloaderMassStorage.txt b/Bootloaders/MassStorage/BootloaderMassStorage.txt
index 7ca7c1f85..19751d3be 100644
--- a/Bootloaders/MassStorage/BootloaderMassStorage.txt
+++ b/Bootloaders/MassStorage/BootloaderMassStorage.txt
@@ -12,6 +12,8 @@
  *
  *  \li Series 7 USB AVRs (AT90USBxxx7)
  *  \li Series 6 USB AVRs (AT90USBxxx6)
+ *  \li Series 4 USB AVRs (ATMEGAxxU4) - <i>See \ref SSec_Aux_Space</i>
+ *  \li Series 2 USB AVRs (AT90USBxx2, ATMEGAxxU2) - <i>See \ref SSec_Aux_Space</i>
  *
  *  \section Sec_Info USB Information:
  *
@@ -49,7 +51,7 @@
  *  firmware image file, to load firmware onto the AVR.
  *
  *  Out of the box this bootloader builds for the AT90USB1287 with an 8KB bootloader section size, and will fit
- *  into 8KB of bootloader space. If you wish to alter this size and/or change the AVR model, you will need to
+ *  into 6KB of bootloader space. If you wish to alter this size and/or change the AVR model, you will need to
  *  edit the MCU, FLASH_SIZE_KB and BOOT_SECTION_SIZE_KB values in the accompanying makefile.
  *
  *  When the bootloader is running, the board's LED(s) will flash at regular intervals to distinguish the
@@ -100,6 +102,22 @@
  *  #define BOOTLOADER_ADDRESS_LENGTH          4
  *  \endcode
  *
+ *  From the application the API support of the bootloader can be detected by reading the FLASH memory bytes located at address
+ *  \c BOOTLOADER_MAGIC_SIGNATURE_START and comparing them to the value \c BOOTLOADER_MAGIC_SIGNATURE. The class of bootloader
+ *  can be determined by reading the FLASH memory bytes located at address \c BOOTLOADER_CLASS_SIGNATURE_START and comparing them
+ *  to the value \c BOOTLOADER_MASS_STORAGE_SIGNATURE. The start address of the bootloader can be retrieved by reading the bytes
+ *  of FLASH memory starting from address \c BOOTLOADER_ADDRESS_START.
+ *
+ *  \subsection SSec_Aux_Space Auxiliary Bootloader Section
+ *  To make the bootloader function on smaller devices (those with a physical bootloader section of smaller than 6KB) a second
+ *  section of memory (called the <i>Auxiliary Bootloader Section</i>) is added before the start of the real bootloader section,
+ *  and is filled with a portion of the bootloader code. This allows smaller devices to run the bootloader, at the cost of an
+ *  additional portion of the device's FLASH (the bootloader section size in KB subtracted from the 6KB total size). A small
+ *  trampoline is inserted at the start of the auxiliary section so that the bootloader will run normally in the case of a blank
+ *  application section.
+ *
+ *  On devices supporting a 8KB bootloader section size, the AUX section is not created in the final binary.
+ *
  *  \subsection SSec_API_MemLayout Device Memory Map
  *  The following illustration indicates the final memory map of the device when loaded with the bootloader.
  *
@@ -121,6 +139,16 @@
  *  |                            |
  *  |                            |
  *  |                            |
+ *  |                            |
+ *  +----------------------------+ FLASHEND - BOOT_SECTION_SIZE - BOOT_AUX_SECTION_SIZE
+ *  | Booloader Start Trampoline |
+ *  | (Not User App. Accessible) |
+ *  +----------------------------+ FLASHEND - BOOT_SECTION_SIZE - BOOT_AUX_SECTION_SIZE + 4
+ *  |                            |
+ *  |     Auxiliary Bootloader   |
+ *  |  Space for Smaller Devices |
+ *  | (Not User App. Accessible) |
+ *  |                            |
  *  +----------------------------+ FLASHEND - BOOT_SECTION_SIZE
  *  |                            |
  *  |   Bootloader Application   |
@@ -138,12 +166,6 @@
  *  +----------------------------+ FLASHEND
  *  \endverbatim
  *
- *  Bootloaders reporting a device release revision number of 1.00 or greater are bootloader API enabled. From the application
- *  the API support of the bootloader can be detected by reading the FLASH memory bytes located at address \c BOOTLOADER_MAGIC_SIGNATURE_START
- *  and comparing them to the value \c BOOTLOADER_MAGIC_SIGNATURE. The class of bootloader can be determined by reading the
- *  FLASH memory bytes located at address \c BOOTLOADER_CLASS_SIGNATURE_START and comparing them to the value \c BOOTLOADER_MASS_STORAGE_SIGNATURE.
- *  The start address of the bootloader can be retrieved by reading the bytes of FLASH memory starting from address \c BOOTLOADER_ADDRESS_START.
- *
  *  \section Sec_Options Project Options
  *
  *  The following defines can be found in this demo, which can control the demo behaviour when defined, or changed in value.
diff --git a/Bootloaders/MassStorage/Config/LUFAConfig.h b/Bootloaders/MassStorage/Config/LUFAConfig.h
index b22e67fbd..fcc3ea819 100644
--- a/Bootloaders/MassStorage/Config/LUFAConfig.h
+++ b/Bootloaders/MassStorage/Config/LUFAConfig.h
@@ -69,7 +69,7 @@
 		#define USE_RAM_DESCRIPTORS
 //		#define USE_FLASH_DESCRIPTORS
 //		#define USE_EEPROM_DESCRIPTORS
-//		#define NO_INTERNAL_SERIAL
+		#define NO_INTERNAL_SERIAL
 		#define FIXED_CONTROL_ENDPOINT_SIZE      8
 		#define DEVICE_STATE_AS_GPIOR            0
 		#define FIXED_NUM_CONFIGURATIONS         1
diff --git a/Bootloaders/MassStorage/Descriptors.c b/Bootloaders/MassStorage/Descriptors.c
index 4de12075a..cbc320f9c 100644
--- a/Bootloaders/MassStorage/Descriptors.c
+++ b/Bootloaders/MassStorage/Descriptors.c
@@ -60,7 +60,7 @@ const USB_Descriptor_Device_t DeviceDescriptor =
 
 	.ManufacturerStrIndex   = NO_DESCRIPTOR,
 	.ProductStrIndex        = NO_DESCRIPTOR,
-	.SerialNumStrIndex      = USE_INTERNAL_SERIAL,
+	.SerialNumStrIndex      = NO_DESCRIPTOR,
 
 	.NumberOfConfigurations = FIXED_NUM_CONFIGURATIONS
 };
@@ -124,17 +124,6 @@ const USB_Descriptor_Configuration_t ConfigurationDescriptor =
 		}
 };
 
-/** Language descriptor structure. This descriptor, located in FLASH memory, is returned when the host requests
- *  the string descriptor with index 0 (the first index). It is actually an array of 16-bit integers, which indicate
- *  via the language ID table available at USB.org what languages the device supports for its string descriptors.
- */
-const USB_Descriptor_String_t LanguageString =
-{
-	.Header                 = {.Size = USB_STRING_LEN(1), .Type = DTYPE_String},
-
-	.UnicodeString          = {LANGUAGE_ID_ENG}
-};
-
 /** This function is called by the library when in device mode, and must be overridden (see library "USB Descriptors"
  *  documentation) by the application code so that the address and size of a requested descriptor can be given
  *  to the USB library. When the device receives a Get Descriptor request on the control endpoint, this function
@@ -145,30 +134,21 @@ uint16_t CALLBACK_USB_GetDescriptor(const uint16_t wValue,
                                     const uint8_t wIndex,
                                     const void** const DescriptorAddress)
 {
-	const uint8_t  DescriptorType   = (wValue >> 8);
-	const uint8_t  DescriptorNumber = (wValue & 0xFF);
+	const uint8_t DescriptorType = (wValue >> 8);
 
 	const void* Address = NULL;
 	uint16_t    Size    = NO_DESCRIPTOR;
 
-	switch (DescriptorType)
+	/* If/Else If chain compiles slightly smaller than a switch case */
+	if (DescriptorType == DTYPE_Device)
+	{
+		Address = &DeviceDescriptor;
+		Size    = sizeof(USB_Descriptor_Device_t);
+	}
+	else if (DescriptorType == DTYPE_Configuration)
 	{
-		case DTYPE_Device:
-			Address = &DeviceDescriptor;
-			Size    = sizeof(USB_Descriptor_Device_t);
-			break;
-		case DTYPE_Configuration:
-			Address = &ConfigurationDescriptor;
-			Size    = sizeof(USB_Descriptor_Configuration_t);
-			break;
-		case DTYPE_String:
-			if (!(DescriptorNumber))
-			{
-					Address = &LanguageString;
-					Size    = pgm_read_byte(&LanguageString.Header.Size);
-			}
-
-			break;
+		Address = &ConfigurationDescriptor;
+		Size    = sizeof(USB_Descriptor_Configuration_t);
 	}
 
 	*DescriptorAddress = Address;
diff --git a/Bootloaders/MassStorage/Descriptors.h b/Bootloaders/MassStorage/Descriptors.h
index 7261fabfa..4460fdab3 100644
--- a/Bootloaders/MassStorage/Descriptors.h
+++ b/Bootloaders/MassStorage/Descriptors.h
@@ -70,7 +70,7 @@
 		uint16_t CALLBACK_USB_GetDescriptor(const uint16_t wValue,
 		                                    const uint8_t wIndex,
 		                                    const void** const DescriptorAddress)
-		                                    ATTR_WARN_UNUSED_RESULT ATTR_NON_NULL_PTR_ARG(3);
+		                                    ATTR_WARN_UNUSED_RESULT ATTR_NON_NULL_PTR_ARG(3) AUX_BOOT_SECTION;
 
 #endif
 
diff --git a/Bootloaders/MassStorage/Lib/SCSI.c b/Bootloaders/MassStorage/Lib/SCSI.c
index 154fe4885..0bb1c7aee 100644
--- a/Bootloaders/MassStorage/Lib/SCSI.c
+++ b/Bootloaders/MassStorage/Lib/SCSI.c
@@ -104,9 +104,6 @@ bool SCSI_DecodeSCSICommand(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo)
 		case SCSI_CMD_READ_CAPACITY_10:
 			CommandSuccess = SCSI_Command_Read_Capacity_10(MSInterfaceInfo);
 			break;
-		case SCSI_CMD_SEND_DIAGNOSTIC:
-			CommandSuccess = SCSI_Command_Send_Diagnostic(MSInterfaceInfo);
-			break;
 		case SCSI_CMD_WRITE_10:
 			CommandSuccess = SCSI_Command_ReadWrite_10(MSInterfaceInfo, DATA_WRITE);
 			break;
@@ -116,6 +113,7 @@ bool SCSI_DecodeSCSICommand(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo)
 		case SCSI_CMD_MODE_SENSE_6:
 			CommandSuccess = SCSI_Command_ModeSense_6(MSInterfaceInfo);
 			break;
+		case SCSI_CMD_SEND_DIAGNOSTIC:
 		case SCSI_CMD_START_STOP_UNIT:
 		case SCSI_CMD_TEST_UNIT_READY:
 		case SCSI_CMD_PREVENT_ALLOW_MEDIUM_REMOVAL:
@@ -227,33 +225,6 @@ static bool SCSI_Command_Read_Capacity_10(USB_ClassInfo_MS_Device_t* const MSInt
 	return true;
 }
 
-/** Command processing for an issued SCSI SEND DIAGNOSTIC command. This command performs a quick check of the Dataflash ICs on the
- *  board, and indicates if they are present and functioning correctly. Only the Self-Test portion of the diagnostic command is
- *  supported.
- *
- *  \param[in] MSInterfaceInfo  Pointer to the Mass Storage class interface structure that the command is associated with
- *
- *  \return Boolean true if the command completed successfully, false otherwise.
- */
-static bool SCSI_Command_Send_Diagnostic(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo)
-{
-	/* Check to see if the SELF TEST bit is not set */
-	if (!(MSInterfaceInfo->State.CommandBlock.SCSICommandData[1] & (1 << 2)))
-	{
-		/* Only self-test supported - update SENSE key and fail the command */
-		SCSI_SET_SENSE(SCSI_SENSE_KEY_ILLEGAL_REQUEST,
-		               SCSI_ASENSE_INVALID_FIELD_IN_CDB,
-		               SCSI_ASENSEQ_NO_QUALIFIER);
-
-		return false;
-	}
-
-	/* Succeed the command and update the bytes transferred counter */
-	MSInterfaceInfo->State.CommandBlock.DataTransferLength = 0;
-
-	return true;
-}
-
 /** Command processing for an issued SCSI READ (10) or WRITE (10) command. This command reads in the block start address
  *  and total number of blocks to process, then calls the appropriate low-level Dataflash routine to handle the actual
  *  reading and writing of the data.
diff --git a/Bootloaders/MassStorage/Lib/SCSI.h b/Bootloaders/MassStorage/Lib/SCSI.h
index 54914f5eb..8eb817fa7 100644
--- a/Bootloaders/MassStorage/Lib/SCSI.h
+++ b/Bootloaders/MassStorage/Lib/SCSI.h
@@ -42,7 +42,6 @@
 
 		#include <LUFA/Drivers/USB/USB.h>
 
-		#include "../BootloaderMassStorage.h"
 		#include "../Descriptors.h"
 		#include "VirtualFAT.h"
 
@@ -69,16 +68,15 @@
 		#define DEVICE_TYPE_BLOCK   0x00
 
 	/* Function Prototypes: */
-		bool SCSI_DecodeSCSICommand(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo);
+		bool SCSI_DecodeSCSICommand(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo) AUX_BOOT_SECTION;
 
 		#if defined(INCLUDE_FROM_SCSI_C)
-			static bool SCSI_Command_Inquiry(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo);
-			static bool SCSI_Command_Request_Sense(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo);
-			static bool SCSI_Command_Read_Capacity_10(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo);
-			static bool SCSI_Command_Send_Diagnostic(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo);
+			static bool SCSI_Command_Inquiry(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo) AUX_BOOT_SECTION;
+			static bool SCSI_Command_Request_Sense(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo) AUX_BOOT_SECTION;
+			static bool SCSI_Command_Read_Capacity_10(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo) AUX_BOOT_SECTION;
 			static bool SCSI_Command_ReadWrite_10(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo,
-			                                      const bool IsDataRead);
-			static bool SCSI_Command_ModeSense_6(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo);
+			                                      const bool IsDataRead) AUX_BOOT_SECTION;
+			static bool SCSI_Command_ModeSense_6(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo) AUX_BOOT_SECTION;
 		#endif
 
 #endif
diff --git a/Bootloaders/MassStorage/Lib/VirtualFAT.c b/Bootloaders/MassStorage/Lib/VirtualFAT.c
index ee0107c1b..41c661ed3 100644
--- a/Bootloaders/MassStorage/Lib/VirtualFAT.c
+++ b/Bootloaders/MassStorage/Lib/VirtualFAT.c
@@ -151,26 +151,28 @@ static void WriteVirtualBlock(const uint16_t BlockNumber)
 
 	if ((BlockNumber >= 4) && (BlockNumber < (4 + FILE_SECTORS(FIRMWARE_FILE_SIZE_BYTES))))
 	{
+		#if (FLASHEND > 0xFFFF)
 		uint32_t WriteFlashAddress = (uint32_t)(BlockNumber - 4) * SECTOR_SIZE_BYTES;
+		#else
+		uint16_t WriteFlashAddress = (uint16_t)(BlockNumber - 4) * SECTOR_SIZE_BYTES;
+		#endif
 
 		for (uint16_t i = 0; i < SECTOR_SIZE_BYTES; i += 2)
 		{
 			if ((WriteFlashAddress % SPM_PAGESIZE) == 0)
 			{
 				/* Erase the given FLASH page, ready to be programmed */
-				boot_page_erase(WriteFlashAddress);
-				boot_spm_busy_wait();
+				BootloaderAPI_ErasePage(WriteFlashAddress);
 			}
 
 			/* Write the next data word to the FLASH page */
-			boot_page_fill(WriteFlashAddress, (BlockBuffer[i + 1] << 8) | BlockBuffer[i]);
+			BootloaderAPI_FillWord(WriteFlashAddress, (BlockBuffer[i + 1] << 8) | BlockBuffer[i]);
 			WriteFlashAddress += 2;
 
 			if ((WriteFlashAddress % SPM_PAGESIZE) == 0)
 			{
 				/* Write the filled FLASH page to memory */
-				boot_page_write(WriteFlashAddress - SPM_PAGESIZE);
-				boot_spm_busy_wait();
+				BootloaderAPI_WritePage(WriteFlashAddress - SPM_PAGESIZE);
 			}
 		}
 	}
@@ -219,10 +221,17 @@ static void ReadVirtualBlock(const uint16_t BlockNumber)
 		default: /* Blocks 4 onwards: Data allocation section */
 			if ((BlockNumber >= 4) && (BlockNumber < (4 + FILE_SECTORS(FIRMWARE_FILE_SIZE_BYTES))))
 			{
+				#if (FLASHEND > 0xFFFF)
 				uint32_t ReadFlashAddress = (uint32_t)(BlockNumber - 4) * SECTOR_SIZE_BYTES;
 
 				for (uint16_t i = 0; i < SECTOR_SIZE_BYTES; i++)
 				  BlockBuffer[i] = pgm_read_byte_far(ReadFlashAddress++);
+				#else
+				uint16_t ReadFlashAddress = (uint16_t)(BlockNumber - 4) * SECTOR_SIZE_BYTES;
+
+				for (uint16_t i = 0; i < SECTOR_SIZE_BYTES; i++)
+				  BlockBuffer[i] = pgm_read_byte(ReadFlashAddress++);
+				#endif
 			}
 
 			break;
@@ -237,8 +246,8 @@ static void ReadVirtualBlock(const uint16_t BlockNumber)
  *  PC via the USB Mass Storage interface.
  *
  *  \param[in] MSInterfaceInfo  Pointer to a structure containing a Mass Storage Class configuration and state
- *  \param[in] BlockAddress  Data block starting address for the write sequence
- *  \param[in] TotalBlocks   Number of blocks of data to write
+ *  \param[in] BlockAddress     Data block starting address for the write sequence
+ *  \param[in] TotalBlocks      Number of blocks of data to write
  */
 void VirtualFAT_WriteBlocks(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo,
                             const uint32_t BlockAddress,
@@ -256,8 +265,8 @@ void VirtualFAT_WriteBlocks(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo,
  *  to the host PC via the USB Mass Storage interface.
  *
  *  \param[in] MSInterfaceInfo  Pointer to a structure containing a Mass Storage Class configuration and state
- *  \param[in] BlockAddress  Data block starting address for the read sequence
- *  \param[in] TotalBlocks   Number of blocks of data to read
+ *  \param[in] BlockAddress     Data block starting address for the read sequence
+ *  \param[in] TotalBlocks      Number of blocks of data to read
  */
 void VirtualFAT_ReadBlocks(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo,
                            const uint32_t BlockAddress,
diff --git a/Bootloaders/MassStorage/Lib/VirtualFAT.h b/Bootloaders/MassStorage/Lib/VirtualFAT.h
index 16b4b738d..8019691dc 100644
--- a/Bootloaders/MassStorage/Lib/VirtualFAT.h
+++ b/Bootloaders/MassStorage/Lib/VirtualFAT.h
@@ -37,9 +37,11 @@
 
 		#include <LUFA/Drivers/USB/USB.h>
 
+		#include "../BootloaderAPI.h"
+
 	/* Macros: */
 		/** Size of the virtual FIRMWARE.BIN file in bytes. */
-		#define FIRMWARE_FILE_SIZE_BYTES  (FLASHEND - (FLASHEND - BOOT_START_ADDR))
+		#define FIRMWARE_FILE_SIZE_BYTES  (FLASHEND - (FLASHEND - BOOT_START_ADDR) - AUX_BOOT_SECTION_SIZE)
 
 		/** Number of sectors that comprise a single logical disk cluster. */
 		#define SECTOR_PER_CLUSTER        4
@@ -144,16 +146,16 @@
 		#if defined(INCLUDE_FROM_VIRTUAL_FAT_C)
 			static void UpdateFAT12ClusterEntry(uint8_t* const FATTable,
 			                                    const uint16_t Index,
-			                                    const uint16_t ChainEntry);
-			static void WriteVirtualBlock(const uint16_t BlockNumber);
-			static void ReadVirtualBlock(const uint16_t BlockNumber);
+			                                    const uint16_t ChainEntry) AUX_BOOT_SECTION;
+			static void WriteVirtualBlock(const uint16_t BlockNumber) AUX_BOOT_SECTION;
+			static void ReadVirtualBlock(const uint16_t BlockNumber) AUX_BOOT_SECTION;
 		#endif
 
 		void VirtualFAT_WriteBlocks(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo,
 		                            const uint32_t BlockAddress,
-		                            uint16_t TotalBlocks);
+		                            uint16_t TotalBlocks) AUX_BOOT_SECTION;
 
 		void VirtualFAT_ReadBlocks(USB_ClassInfo_MS_Device_t* const MSInterfaceInfo,
 		                           const uint32_t BlockAddress,
-		                           uint16_t TotalBlocks);
+		                           uint16_t TotalBlocks) AUX_BOOT_SECTION;
 #endif
diff --git a/Bootloaders/MassStorage/makefile b/Bootloaders/MassStorage/makefile
index 68b26b1bd..c23e62f19 100644
--- a/Bootloaders/MassStorage/makefile
+++ b/Bootloaders/MassStorage/makefile
@@ -27,20 +27,33 @@ LD_FLAGS     = -Wl,--section-start=.text=$(BOOT_START_OFFSET) $(BOOT_API_LD_FLAG
 # match the target's total FLASH size and the bootloader size set in the

 # device's fuses.

 FLASH_SIZE_KB         = 128

-BOOT_SECTION_SIZE_KB  = 8

+BOOT_SECTION_SIZE_KB  = 4

 

 # Bootloader address calculation formulas

 # Do not modify these macros, but rather modify the dependent values above.

 CALC_ADDRESS_IN_HEX   = $(shell printf "0x%X" $$(( $(1) )) )

 BOOT_START_OFFSET     = $(call CALC_ADDRESS_IN_HEX, ($(FLASH_SIZE_KB) - $(BOOT_SECTION_SIZE_KB)) * 1024 )

-BOOT_SEC_OFFSET       = $(call CALC_ADDRESS_IN_HEX, ($(FLASH_SIZE_KB) * 1024) - $(strip $(1)) )

+BOOT_SEC_OFFSET       = $(call CALC_ADDRESS_IN_HEX, ($(FLASH_SIZE_KB) * 1024) - ($(strip $(1))) )

 

 # Bootloader linker section flags for relocating the API table sections to

 # known FLASH addresses - these should not normally be user-edited.

-BOOT_SECTION_LD_FLAG  = -Wl,--section-start=.apitable_$(strip $(1))=$(call BOOT_SEC_OFFSET, $(3)) -Wl,--undefined=BootloaderAPI_$(strip $(2))

-BOOT_API_LD_FLAGS     = $(call BOOT_SECTION_LD_FLAG, trampolines, Trampolines, 96)

-BOOT_API_LD_FLAGS    += $(call BOOT_SECTION_LD_FLAG, jumptable,   JumpTable,   32)

-BOOT_API_LD_FLAGS    += $(call BOOT_SECTION_LD_FLAG, signatures,  Signatures,  8)

+BOOT_SECTION_LD_FLAG  = -Wl,--section-start=$(strip $(1))=$(call BOOT_SEC_OFFSET, $(3)) -Wl,--undefined=$(strip $(2))

+BOOT_API_LD_FLAGS     = $(call BOOT_SECTION_LD_FLAG, .apitable_trampolines, BootloaderAPI_Trampolines, 96)

+BOOT_API_LD_FLAGS    += $(call BOOT_SECTION_LD_FLAG, .apitable_jumptable,   BootloaderAPI_JumpTable,   32)

+BOOT_API_LD_FLAGS    += $(call BOOT_SECTION_LD_FLAG, .apitable_signatures,  BootloaderAPI_Signatures,  8)

+

+# Check if the bootloader needs an AUX section, located before the real bootloader section to store some of the

+# bootloader code. This is required for 32KB and smaller devices, where the actual bootloader is 6KB but the maximum

+# bootloader section size is 4KB. The actual usable application space will be reduced by 6KB for these devices.

+ifeq ($(BOOT_SECTION_SIZE_KB),8)

+  CC_FLAGS           += -DAUX_BOOT_SECTION='' -DAUX_BOOT_SECTION_SIZE=0

+else

+  AUX_BOOT_SECTION_KB = (6 - $(BOOT_SECTION_SIZE_KB))

+

+  CC_FLAGS           += -DAUX_BOOT_SECTION='__attribute__((section(".boot_aux")))' -DAUX_BOOT_SECTION_SIZE='($(AUX_BOOT_SECTION_KB) * 1024)'

+  LD_FLAGS           += -Wl,--section-start=.boot_aux=$(call BOOT_SEC_OFFSET, (($(BOOT_SECTION_SIZE_KB) + $(AUX_BOOT_SECTION_KB)) * 1024 - 16))

+  LD_FLAGS           += $(call BOOT_SECTION_LD_FLAG, .boot_aux_trampoline, Boot_AUX_Trampoline, ($(BOOT_SECTION_SIZE_KB) + $(AUX_BOOT_SECTION_KB)) * 1024)

+endif

 

 # Default target

 all: