busybox shell doesn't come up or get stuck.. where should I look or how should I debug it?

[Chan Kim]

Hi all,

I'm trying to boot linux with minimal config on our FPGA board which is
under development.
After months of trying (but I tried this intermittently) I think I'm about
to see the shell prompt.
(there was a bug in interconnect driver that I found yesterday, this caused
a long delay)

Anyway, when I run linux kernel on a qemu machine, the boot process ends
like this at the shell prompt.
(The echo '### INIT SCRIPT ###' was put in /init script which is in the
initramfs)
    
    Run /init as init process
    ### INIT SCRIPT ###
    mount: mounting none on /tmp failed: Invalid argument
    
    This boot took 2.12 seconds
    
    /bin/sh: can't access tty; job control turned off
    / # 
    / #

Now, when I run it on our FPGA board using u-boot, it ends like this.
    
    Run /init as init process
    ### INIT SCRIPT ###
    mount: mounting none on /tmp failed: Invalid argument
    
    This boot took 0.00 seconds
    
    /bin/sh: can't acce
    
So it seems this init_kernel thread executes /init and /init excutes /bin/sh
at the end.

this is the /init script.

	#!/bin/sh
	echo "### INIT SCRIPT ###"
	mkdir /proc /sys /tmp
	mount -t proc none /proc
	mount -t sysfs none /sys
	mount -t tmpfs none /tmp
	echo -e "\nThis boot took $(cut -d' ' -f1 /proc/uptime) seconds\n"

	#ifconfig eth0 10.0.2.15 netmask 255.255.255.0 up
	#route add default gw 10.0.2.2

	exec /bin/sh

Somehow the busybox applet /bin/sh is stuck somewhere.
Can anybody tell me where I should look? Or how to debug this?

Thanks in advance!

Chan Kim

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