Blackfin: fix crash when booting from external memory

When testing a u-boot binary that hasn't been booted from the bootrom, we
have to make sure the bootstruct structure has sane storage space.  If we
don't, the initcode will crash when it tries to dereference an invalid
pointer.
Signed-off-by: NMike Frysinger <vapier@gentoo.org>

cpu/blackfin/initcode.c

@@ -249,6 +249,8 @@ static inline void serial_putc(char c)
 BOOTROM_CALLED_FUNC_ATTR
 void initcode(ADI_BOOT_DATA *bootstruct)
 {
+	ADI_BOOT_DATA bootstruct_scratch;
+
 	/* Save the clock pieces that are used in baud rate calculation */
 	unsigned int sdivB, divB, vcoB;
 	serial_init();
@@ -260,6 +262,13 @@ void initcode(ADI_BOOT_DATA *bootstruct)
 
 	serial_putc('A');
 
+	/* If the bootstruct is NULL, then it's because we're loading
+	 * dynamically and not via LDR (bootrom).  So set the struct to
+	 * some scratch space.
+	 */
+	if (!bootstruct)
+		bootstruct = &bootstruct_scratch;
+
 #ifdef CONFIG_HW_WATCHDOG
 # ifndef CONFIG_HW_WATCHDOG_TIMEOUT_INITCODE
 #  define CONFIG_HW_WATCHDOG_TIMEOUT_INITCODE 20000

cpu/blackfin/start.S

@@ -131,6 +131,7 @@ ENTRY(_start)
 	r3.h = 0x2000;
 	cc = r5 < r3 (iu);
 	if cc jump .Ldma_and_reprogram;
+	r0 = 0 (x);	/* set bootstruct to NULL */
 	call _initcode;
 	jump .Lprogrammed;
 
@@ -147,6 +148,7 @@ ENTRY(_start)
 	r1 = r1 + r5;	/* ... to current (not load) address of initcode */
 	p3 = r0;
 	call _dma_memcpy_nocache;
+	r0 = 0 (x);	/* set bootstruct to NULL */
 	call (p3);
 
 	/* Since we reprogrammed SCLK, we need to update the serial divisor */