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Commit bb0bb3b6 authored by Paul Mackerras's avatar Paul Mackerras Committed by Linus Torvalds
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[PATCH] ppc32: Kill init on unhandled synchronous signals 



This is a patch that I have had in my tree for ages.  If init causes
an exception that raises a signal, such as a SIGSEGV, SIGILL or
SIGFPE, and it hasn't registered a handler for it, we don't deliver
the signal, since init doesn't get any signals that it doesn't have a
handler for.  But that means that we just return to userland and
generate the same exception again immediately.  With this patch we
print a message and kill init in this situation.

This is very useful when you have a bug in the kernel that means that
init doesn't get as far as executing its first instruction. :)
Without this patch the system hangs when it gets to starting the
userland init; with it you at least get a message giving you a clue
about what has gone wrong.

Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 1e63bc73

arch/ppc/kernel/traps.c

+22 −0
Original line number Diff line number Diff line
@@ -118,6 +118,28 @@ void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr) 
	info.si_code = code;

	info.si_addr = (void __user *) addr;

	force_sig_info(signr, &info, current);



	/*

	 * Init gets no signals that it doesn't have a handler for.

	 * That's all very well, but if it has caused a synchronous

	 * exception and we ignore the resulting signal, it will just

	 * generate the same exception over and over again and we get

	 * nowhere.  Better to kill it and let the kernel panic.

	 */

	if (current->pid == 1) {

		__sighandler_t handler;



		spin_lock_irq(&current->sighand->siglock);

		handler = current->sighand->action[signr-1].sa.sa_handler;

		spin_unlock_irq(&current->sighand->siglock);

		if (handler == SIG_DFL) {

			/* init has generated a synchronous exception

			   and it doesn't have a handler for the signal */

			printk(KERN_CRIT "init has generated signal %d "

			       "but has no handler for it\n", signr);

			do_exit(signr);

		}

	}

}



/*

arch/ppc/mm/fault.c

+1 −5
Original line number Diff line number Diff line
@@ -278,11 +278,7 @@ bad_area: 


	/* User mode accesses cause a SIGSEGV */

	if (user_mode(regs)) {

		info.si_signo = SIGSEGV;

		info.si_errno = 0;

		info.si_code = code;

		info.si_addr = (void __user *) address;

		force_sig_info(SIGSEGV, &info, current);

		_exception(SIGSEGV, regs, code, address);

		return 0;

	}

include/asm-ppc/system.h

+1 −0
Original line number Diff line number Diff line
@@ -88,6 +88,7 @@ extern void *cacheable_memcpy(void *, const void *, unsigned int); 
extern int do_page_fault(struct pt_regs *, unsigned long, unsigned long);

extern void bad_page_fault(struct pt_regs *, unsigned long, int);

extern void die(const char *, struct pt_regs *, long);

extern void _exception(int, struct pt_regs *, int, unsigned long);

#ifdef CONFIG_BOOKE_WDT

extern u32 booke_wdt_enabled;

extern u32 booke_wdt_period;