This is a note to let you know that I've just added the patch titled
kprobes/x86: Disable preemption in ftrace-based jprobes
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kprobes-x86-disable-preemption-in-ftrace-based-jprobes.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Wed Dec 6 17:39:55 CET 2017
From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Date: Tue, 19 Sep 2017 19:01:40 +0900
Subject: kprobes/x86: Disable preemption in ftrace-based jprobes
From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
[ Upstream commit 5bb4fc2d8641219732eb2bb654206775a4219aca ]
Disable preemption in ftrace-based jprobe handlers as
described in Documentation/kprobes.txt:
"Probe handlers are run with preemption disabled."
This will fix jprobes behavior when CONFIG_PREEMPT=y.
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul E . McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/150581530024.32348.9863783558598926771.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/kprobes/ftrace.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -26,7 +26,7 @@
#include "common.h"
static nokprobe_inline
-int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
+void __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb, unsigned long orig_ip)
{
/*
@@ -41,20 +41,21 @@ int __skip_singlestep(struct kprobe *p,
__this_cpu_write(current_kprobe, NULL);
if (orig_ip)
regs->ip = orig_ip;
- return 1;
}
int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
- if (kprobe_ftrace(p))
- return __skip_singlestep(p, regs, kcb, 0);
- else
- return 0;
+ if (kprobe_ftrace(p)) {
+ __skip_singlestep(p, regs, kcb, 0);
+ preempt_enable_no_resched();
+ return 1;
+ }
+ return 0;
}
NOKPROBE_SYMBOL(skip_singlestep);
-/* Ftrace callback handler for kprobes */
+/* Ftrace callback handler for kprobes -- called under preepmt disabed */
void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct pt_regs *regs)
{
@@ -77,13 +78,17 @@ void kprobe_ftrace_handler(unsigned long
/* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
regs->ip = ip + sizeof(kprobe_opcode_t);
+ /* To emulate trap based kprobes, preempt_disable here */
+ preempt_disable();
__this_cpu_write(current_kprobe, p);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
- if (!p->pre_handler || !p->pre_handler(p, regs))
+ if (!p->pre_handler || !p->pre_handler(p, regs)) {
__skip_singlestep(p, regs, kcb, orig_ip);
+ preempt_enable_no_resched();
+ }
/*
* If pre_handler returns !0, it sets regs->ip and
- * resets current kprobe.
+ * resets current kprobe, and keep preempt count +1.
*/
}
end:
Patches currently in stable-queue which might be from mhiramat@xxxxxxxxxx are
queue-4.9/kprobes-use-synchronize_rcu_tasks-for-optprobe-with-config_preempt-y.patch
queue-4.9/kprobes-x86-disable-preemption-in-ftrace-based-jprobes.patch