The patch titled
kprobe-booster: disable in preemptible kernel
has been added to the -mm tree. Its filename is
kprobe-booster-disable-in-preemptible-kernel.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: kprobe-booster: disable in preemptible kernel
From: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
The kprobe-booster's safety check against preemption does not work well
now, because the preemption count has been modified by read_rcu_lock() in
atomic_notifier_call_chain() before we check it. So, I'd like to prevent
boosting kprobe temporarily if the kernel is preemptable.
Now we are searching for the good solution.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Cc: Prasanna S Panchamukhi <prasanna@xxxxxxxxxx>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
arch/i386/kernel/kprobes.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff -puN arch/i386/kernel/kprobes.c~kprobe-booster-disable-in-preemptible-kernel arch/i386/kernel/kprobes.c
--- a/arch/i386/kernel/kprobes.c~kprobe-booster-disable-in-preemptible-kernel
+++ a/arch/i386/kernel/kprobes.c
@@ -256,11 +256,6 @@ static int __kprobes kprobe_handler(stru
int ret = 0;
kprobe_opcode_t *addr;
struct kprobe_ctlblk *kcb;
-#ifdef CONFIG_PREEMPT
- unsigned pre_preempt_count = preempt_count();
-#else
- unsigned pre_preempt_count = 1;
-#endif
addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
@@ -338,13 +333,15 @@ static int __kprobes kprobe_handler(stru
return 1;
ss_probe:
- if (pre_preempt_count && p->ainsn.boostable == 1 && !p->post_handler){
+#ifndef CONFIG_PREEMPT
+ if (p->ainsn.boostable == 1 && !p->post_handler){
/* Boost up -- we can execute copied instructions directly */
reset_current_kprobe();
regs->eip = (unsigned long)p->ainsn.insn;
preempt_enable_no_resched();
return 1;
}
+#endif
prepare_singlestep(p, regs);
kcb->kprobe_status = KPROBE_HIT_SS;
return 1;
_
Patches currently in -mm which might be from masami.hiramatsu.pt@xxxxxxxxxxx are
kprobe-booster-disable-in-preemptible-kernel.patch
-
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