[S390] kprobes breaks BUG_ON (f794c827) · Commits · 戴 / test

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:

Martin Schwidefsky <schwidefsky@de.ibm.com>

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);

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