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Commit f794c827 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

[S390] kprobes breaks BUG_ON 



The illegal operation handler calls the die notifier with DIE_BPT to
let kprobes pick up its breakpoint. If kprobes does not find its
breakpoint it returns NOTIFY_STOP instead of NOTIFY_DONE.
Since we use stop_machine_run on s390 to arm/disarm the kprobes
breakpoints the race that kprobe_handler tries to solve by checking
for the kprobes breakpoints does not exist. Removing the check makes
BUG_ON working again.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent c3442e29

arch/s390/kernel/kprobes.c

+7 −14
Original line number Diff line number Diff line
@@ -337,21 +337,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
	}



	p = get_kprobe(addr);

	if (!p) {

		if (*addr != BREAKPOINT_INSTRUCTION) {

	if (!p)

		/*

			 * The breakpoint instruction was removed right

			 * after we hit it.  Another cpu has removed

			 * either a probepoint or a debugger breakpoint

			 * at this address.  In either case, no further

			 * handling of this interrupt is appropriate.

			 *

		 * No kprobe at this address. The fault has not been

		 * caused by a kprobe breakpoint. The race of breakpoint

		 * vs. kprobe remove does not exist because on s390 we

		 * use stop_machine_run to arm/disarm the breakpoints.

		 */

			ret = 1;

		}

		/* Not one of ours: let kernel handle it */

		goto no_kprobe;

	}



	kcb->kprobe_status = KPROBE_HIT_ACTIVE;

	set_current_kprobe(p, regs, kcb);