Busybox won't init

[Denys Vlasenko]

On Thursday 04 November 2010 06:34, Matt Johnson wrote:
> 
> Hi.  I need some assistance with getting busybox working on an ARM920t based board (custom s3c2410, similar to QT2410 or SMDK2410).  I have a good working toolchain (built by crosstool-ng), u-boot and kernel (2.6.36).  I am using buildroot to make busybox 1.17.3 with the defconfig.
>  
> When booting my kernel, the last step is to call /linuxrc - which is a link to busybox.  Busybox outputs absolutly nothing, but just exits.  The kernel then panics because init was killed.  It looks like this:
>  
> ... (normal kernel startup messages)
> Freeing init memory: 128K
> ... (init is here, calling busybox, which just quits with no output)
> Kernel panic - not syncing: Attempted to kill init!
> ... (then the kernel stack unwinds and the box halts) ...
>  
> I've already read the FAQ, and yes - "hello world" works fine.  More than that, if I set init=/bin/busybox I get the busybox help page, so I know that it is compiled correctly for my platform.  I get the same results compiling outside of buildroot directly from the toolchain.  I've also verified that the kernel is built with EABI.
>  
> What are next steps to debug this?

You came pretty far in the debugging already,
and your mail is an excellent example how to report
problems properly.

I guess at this point you need to resort to adding
debug printouts to init's main, a-la:

int init_main(int argc UNUSED_PARAM, char **argv)
{
bb_error_msg("%s:%u", __func__, __LINE__);
        die_sleep = 30 * 24*60*60; /* if xmalloc would ever die... */

        if (argv[1] && strcmp(argv[1], "-q") == 0) {
bb_error_msg("%s:%u", __func__, __LINE__);
                return kill(1, SIGHUP);
        }
bb_error_msg("%s:%u", __func__, __LINE__);
...
        /* Figure out where the default console should be */
        console_init();
bb_error_msg("%s:%u", __func__, __LINE__);
        set_sane_term();
        xchdir("/");
bb_error_msg("%s:%u", __func__, __LINE__);
        setsid();
bb_error_msg("%s:%u", __func__, __LINE__);
...


> Are there any arguments I can pass or set in the config that would output something useful for debugging? 

Try disabling FEATURE_EXTRA_QUIET, with it off
you should see this message emitted pretty early
in init's lifetime:

#if !ENABLE_FEATURE_EXTRA_QUIET
        /* Hello world */
        message(L_CONSOLE | L_LOG, "init started: %s", bb_banner);
#endif

-- 
vda