microblaze: Fix bug with passing command line

When u-boot passes control over to Linux it places the Linux command
line between to the end of __init_end. When space between
__init_end and __bss_start is not COMMAND_LINE_SIZE then
the part of cmdline can be lost.
In extreme case if __init_end == __bss_start u-boot can't pass
any cmdline to Linux kernel.

This patch fix this issue by copying cmd line directly to
cmd_line char array which is placed in data section.

Reported-by: David Mc Andrew <david.mcandrew@xilinx.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/kernel/head.S

@@ -109,20 +109,24 @@ no_fdt_arg:
 #ifndef CONFIG_CMDLINE_BOOL
 /*
  * handling command line
- * copy command line to __init_end. There is space for storing command line.
+ * copy command line directly to cmd_line placed in data section.
  */
+	beqid	r5, skip	/* Skip if NULL pointer */
 	or	r6, r0, r0		/* incremment */
-	ori	r4, r0, __init_end	/* load address of command line */
+	ori	r4, r0, cmd_line	/* load address of command line */
 	tophys(r4,r4)			/* convert to phys address */
 	ori	r3, r0, COMMAND_LINE_SIZE - 1 /* number of loops */
 _copy_command_line:
-	lbu	r2, r5, r6 /* r2=r5+r6 - r5 contain pointer to command line */
-	sb	r2, r4, r6		/* addr[r4+r6]= r2*/
+	/* r2=r5+r6 - r5 contain pointer to command line */
+	lbu		r2, r5, r6
+	beqid	r2, skip		/* Skip if no data */
+	sb		r2, r4, r6		/* addr[r4+r6]= r2*/
 	addik	r6, r6, 1		/* increment counting */
 	bgtid	r3, _copy_command_line	/* loop for all entries       */
-	addik	r3, r3, -1		/* descrement loop */
+	addik	r3, r3, -1		/* decrement loop */
 	addik	r5, r4, 0		/* add new space for command line */
 	tovirt(r5,r5)
+skip:
 #endif /* CONFIG_CMDLINE_BOOL */
 
 #ifdef NOT_COMPILE

arch/microblaze/kernel/setup.c

@@ -40,7 +40,12 @@ DEFINE_PER_CPU(unsigned int, R11_SAVE);	/* Temp variable for entry */
 DEFINE_PER_CPU(unsigned int, CURRENT_SAVE);	/* Saved current pointer */
 
 unsigned int boot_cpuid;
-char cmd_line[COMMAND_LINE_SIZE];
+/*
+ * Placed cmd_line to .data section because can be initialized from
+ * ASM code. Default position is BSS section which is cleared
+ * in machine_early_init().
+ */
+char cmd_line[COMMAND_LINE_SIZE] __attribute__ ((section(".data")));
 
 void __init setup_arch(char **cmdline_p)
 {
@@ -130,12 +135,6 @@ void __init machine_early_init(const char *cmdline, unsigned int ram,
 	memset(__bss_start, 0, __bss_stop-__bss_start);
 	memset(_ssbss, 0, _esbss-_ssbss);
 
-	/* Copy command line passed from bootloader */
-#ifndef CONFIG_CMDLINE_BOOL
-	if (cmdline && cmdline[0] != '\0')
-		strlcpy(cmd_line, cmdline, COMMAND_LINE_SIZE);
-#endif
-
 	lockdep_init();
 
 /* initialize device tree for usage in early_printk */