Implement a bootloader.

This bootloader is now the application at 0x08000000 (FLASH start),
which the STM32 will execute upon reset.

The other applications are now loaded at 0x08030000 (128 KB into the
flash) and will never get started unless the bootloader has been
programmed into flash too.

2 files changed, 96 insertions, 0 deletions

diff --git a/projects/bootloader/Makefile b/projects/bootloader/Makefile
new file mode 100644
index 0000000..7cef633
--- /dev/null
+++ b/projects/bootloader/Makefile
@@ -0,0 +1,18 @@
+PROG = bootloader
+
+all: $(PROG:=.elf)
+
+%.elf: %.o $(BOARD_OBJS) $(LIBS)
+	$(CC) $(CFLAGS) $^ -o $@ -T$(BOOTLOADER_LDSCRIPT) -g -Wl,-Map=$*.map
+	$(OBJCOPY) -O ihex $*.elf $*.hex
+	$(OBJCOPY) -O binary $*.elf $*.bin
+	$(OBJDUMP) -St $*.elf >$*.lst
+	$(SIZE) $*.elf
+
+clean:
+	rm -f *.o
+	rm -f *.elf
+	rm -f *.hex
+	rm -f *.bin
+	rm -f *.map
+	rm -f *.lst
diff --git a/projects/bootloader/bootloader.c b/projects/bootloader/bootloader.c
new file mode 100644
index 0000000..1450c1a
--- /dev/null
+++ b/projects/bootloader/bootloader.c
@@ -0,0 +1,78 @@
+/*
+ * Bootloader to either install new firmware received from the MGMT UART,
+ * or jump to previously installed firmware.
+ *
+ */
+#include "stm32f4xx_hal.h"
+#include "stm-init.h"
+#include "stm-led.h"
+#include "stm-uart.h"
+
+/* Magic bytes to signal the bootloader it should jump to the firmware
+ * instead of trying to receive a new firmware using the MGMT UART.
+ */
+#define HARDWARE_EARLY_DFU_JUMP   0xBADABADA
+
+/* symbols defined in the linker script (STM32F429BI.ld) */
+extern uint32_t CRYPTECH_FIRMWARE_START;
+extern uint32_t CRYPTECH_FIRMWARE_END;
+extern uint32_t CRYPTECH_DFU_CONTROL;
+
+/* Linker symbols are strange in C. Make regular pointers for sanity. */
+__IO uint32_t *dfu_control = &CRYPTECH_DFU_CONTROL;
+__IO uint32_t *dfu_firmware = &CRYPTECH_FIRMWARE_START;
+/* The first word in the firmware is an address to the stack (msp) */
+__IO uint32_t *dfu_msp_ptr = &CRYPTECH_FIRMWARE_START;
+/* The second word in the firmware is a pointer to the code
+ * (points at the Reset_Handler from the linker script).
+ */
+__IO uint32_t *dfu_code_ptr = &CRYPTECH_FIRMWARE_START + 1;
+
+typedef  void (*pFunction)(void);
+
+/* This is it's own function to make it more convenient to set a breakpoint at it in gdb */
+void do_early_dfu_jump(void)
+{
+    pFunction loaded_app = (pFunction) *dfu_code_ptr;
+    /* Set the stack pointer to the correct one for the firmware */
+    __set_MSP(*dfu_msp_ptr);
+    /* Set the Vector Table Offset Register */
+    SCB->VTOR = (uint32_t) dfu_firmware;
+    loaded_app();
+    while (1);
+}
+
+int
+main()
+{
+    int i;
+
+    /* Check if we've just rebooted in order to jump to the firmware. */
+    if (*dfu_control == HARDWARE_EARLY_DFU_JUMP) {
+	*dfu_control = 0;
+	do_early_dfu_jump();
+    }
+
+    stm_init();
+
+    uart_send_string2(STM_UART_MGMT, (char *) "This is the bootloader speaking...");
+
+    /* This is where uploading of new firmware over UART could happen */
+
+    led_on(LED_BLUE);
+    for (i = 0; i < 10; i++) {
+	HAL_Delay(100);
+	led_toggle(LED_BLUE);
+    }
+
+    /* Set dfu_control to the magic value that will cause the us to call do_early_dfu_jump
+     * after rebooting back into this main() function.
+     */
+    *dfu_control = HARDWARE_EARLY_DFU_JUMP;
+
+    uart_send_string2(STM_UART_MGMT, (char *) "loading firmware\r\n");
+
+    /* De-initialize hardware by rebooting */
+    HAL_NVIC_SystemReset();
+    while (1) {};
+}