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Message-ID: <20070305223910.GA22630@skybase>
Date: Mon, 5 Mar 2007 23:39:11 +0100
From: Martin Schwidefsky <schwidefsky@...ibm.com>
To: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: [S390] kprobes breaks BUG_ON
From: Martin Schwidefsky <schwidefsky@...ibm.com>
[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: Martin Schwidefsky <schwidefsky@...ibm.com>
---
arch/s390/kernel/kprobes.c | 21 +++++++--------------
1 files changed, 7 insertions(+), 14 deletions(-)
diff -urpN linux-2.6/arch/s390/kernel/kprobes.c linux-2.6-patched/arch/s390/kernel/kprobes.c
--- linux-2.6/arch/s390/kernel/kprobes.c 2007-03-05 22:51:29.000000000 +0100
+++ linux-2.6-patched/arch/s390/kernel/kprobes.c 2007-03-05 22:51:47.000000000 +0100
@@ -337,21 +337,14 @@ static int __kprobes kprobe_handler(stru
}
p = get_kprobe(addr);
- if (!p) {
- if (*addr != BREAKPOINT_INSTRUCTION) {
- /*
- * 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.
- *
- */
- ret = 1;
- }
- /* Not one of ours: let kernel handle it */
+ if (!p)
+ /*
+ * 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.
+ */
goto no_kprobe;
- }
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
set_current_kprobe(p, regs, kcb);
-
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