vmunix: sendsig: bad user stack

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2 total messages Started by Brian Fitzgerald Fri, 18 Dec 1992 17:27

#2425

Author: Brian Fitzgerald
Date: Fri, 18 Dec 1992 17:27

25 lines
1053 bytes

I have found that if I startup a shell, but interrupt it immediately
with ^C, I get:

fitzgb@mml0.meche /fitzgb (22) bash -norc
^C^C
^C^C^C^C^CIllegal instruction (core dumped)

In /var/adm/messages I get 

Dec 18 00:56:31 mml0 vmunix: sendsig: bad user stack pid=6856, sig=11
Dec 18 00:56:31 mml0 vmunix: usp is ffffffdc, action is 3eac0, upc is e00482e

I'm interested to know ...

--  Why would interrupting a program during startup result in an illegal
instruction signal?

--  What do the log messages mean?

--  Why does the log message say "sig=11" (segmentation fault), but
"Illegal instruction", (signal 4), is printed on my terminal.

Sun3 os 4.1.1

Brian

Re: vmunix: sendsig: bad user stack

#2426

Author: Guy Harris
Date: Sat, 19 Dec 1992 04:34

27 lines
1171 bytes

>--  Why would interrupting a program during startup result in an illegal
>instruction signal?

See below.

>--  What do the log messages mean?

See below.

>--  Why does the log message say "sig=11" (segmentation fault), but
>"Illegal instruction", (signal 4), is printed on my terminal.

Because:

	1) "bash" is catching SIGSEGV;

	2) it did something that caused a SIGSEGV when you ^C'ed it;

	3) the user stack pointer was bad (the address 0xffffffdc looks
	   bogus), so the kernel couldn't deliver the SIGSEGV to the
	   process (it has to push stuff onto the stack to do so);

	4) if that happens, the kernel sends a SIGILL to the process to
	   kill it off, and logs some messages to indicate why it's
	   doing so.

Could be a bug somewhere in "bash"....

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