Re: __stack_start for ColdFire uClinux

On 4 Oct 2012, at 1:05 PM, Larry Baker wrote:

> I am still puzzled, though, why uClinux is silent when a program is aborted when it receives an unhandled fatal signal.  Mainline Linux (really the shell?) prints out a message like
> 
>> [root@atompc sdk]# ./SIGILL
>> Illegal instruction
> 
> (SIGILL.c is the example program from http://en.wikipedia.org/wiki/SIGILL.)  After a reboot of uClinux, I get nothing
> 
>> / # SIGILL
> 
> I have to enable print-fatal-signals as before to see anything:
> 
>> / # echo 1 >/proc/sys/kernel/print-fatal-signals
>> / # SIGILL
>> SIGILL/79: potentially unexpected fatal signal 4.
>> 
>> 
>> Format 04  Vector: 002c  PC: 4052e544  Status: 0000    Not tainted
>> ORIG_D0: ffffffff  D0: 4052e544  A2: 4052ff60  A1: 4052e4ec
>> A0: 4052e544  D5: 4052e524  D4: 00000000
>> D3: 00000000  D2: 00000001  D1: 0000002f
>> USP: 4052ff04
> 
> Is this a uClinux thing?  Or, a BusyBox (my uClinux shell) thing?


I'll answer my own question.

It is the shell that prints out the "Illegal instruction" message.  I found the code in bash that does that and added it to the BusyBox hush shell.  The SDK I use has a rather old BusyBox, 1.13.3.  The hush shell is in busybox-1.13.3/shell/hush.c.  checkjobs() waits for all child processes -- there is no distinction made between job control jobs and non-job control jobs like there is in bash.  There is already code there that can be (hand) enabled to be verbose about what happens to a job.  Enabling that also makes hush very chatty.  So, I added an #else clause for the #if DEBUG_JOBS conditional code in checkjobs() to mimic bash's behavior.  Here's the patch for busybox-1.13.3:

--- busybox-1.13.3/shell/hush.c
+++ busybox-1.13.3-patched/shell/hush.c
@@ -1720,2 +1720,13 @@
 					childpid, WEXITSTATUS(status));
> +#else
> +		if ((WIFSTOPPED (status) == 0) && WIFSIGNALED (status)) {
> +			int sig = WTERMSIG (status);
> +			if ((sig != SIGINT) && (sig != SIGPIPE)) {
> +				char *s = strsignal (sig);
> +				if ( s != NULL )
> +					fprintf (stderr, "%s\n", s);
> +				else
> +					fprintf (stderr, "Unknown signal: %d\n", sig);
> +			}
> +		}
>  #endif

With this patched hush, I get what I am used to seeing:

> / # trap
> Illegal instruction

> / # SIGILL
> Illegal instruction

Now I can go back and find out where the applications I use are failing.  I suspect stack overflows, which my implementation of gcc -stack-check-symbol=__stack_start for non-68020 (e.g., ColdFire) processors can catch now.

Larry Baker
US Geological Survey
650-329-5608
[email protected]

_______________________________________________
uClinux-dev mailing list
[email protected]
http://mailman.uclinux.org/mailman/listinfo/uclinux-dev
This message was resent by [email protected]
To unsubscribe see:
http://mailman.uclinux.org/mailman/options/uclinux-dev