* [PATCH] trace: reenable preemption if we modify the ip
@ 2017-12-16 2:42 Josef Bacik
2017-12-17 19:49 ` Daniel Borkmann
2017-12-18 7:29 ` Masami Hiramatsu
0 siblings, 2 replies; 3+ messages in thread
From: Josef Bacik @ 2017-12-16 2:42 UTC (permalink / raw)
To: netdev, mhiramat, ast, daniel, darrick.wong, linux-kernel; +Cc: Josef Bacik
From: Josef Bacik <jbacik@fb.com>
Things got moved around between the original bpf_override_return patches
and the final version, and now the ftrace kprobe dispatcher assumes if
you modified the ip that you also enabled preemption. Make a comment of
this and enable preemption, this fixes the lockdep splat that happened
when using this feature.
Signed-off-by: Josef Bacik <jbacik@fb.com>
---
kernel/trace/trace_kprobe.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 5db849809a56..91f4b57dab82 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1322,8 +1322,15 @@ static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs)
if (tk->tp.flags & TP_FLAG_TRACE)
kprobe_trace_func(tk, regs);
#ifdef CONFIG_PERF_EVENTS
- if (tk->tp.flags & TP_FLAG_PROFILE)
+ if (tk->tp.flags & TP_FLAG_PROFILE) {
ret = kprobe_perf_func(tk, regs);
+ /*
+ * The ftrace kprobe handler leaves it up to us to re-enable
+ * preemption here before returning if we've modified the ip.
+ */
+ if (ret)
+ preempt_enable_no_resched();
+ }
#endif
return ret;
}
--
2.7.5
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] trace: reenable preemption if we modify the ip
2017-12-16 2:42 [PATCH] trace: reenable preemption if we modify the ip Josef Bacik
@ 2017-12-17 19:49 ` Daniel Borkmann
2017-12-18 7:29 ` Masami Hiramatsu
1 sibling, 0 replies; 3+ messages in thread
From: Daniel Borkmann @ 2017-12-17 19:49 UTC (permalink / raw)
To: Josef Bacik, netdev, mhiramat, ast, darrick.wong, linux-kernel
Cc: Josef Bacik
On 12/16/2017 03:42 AM, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
>
> Things got moved around between the original bpf_override_return patches
> and the final version, and now the ftrace kprobe dispatcher assumes if
> you modified the ip that you also enabled preemption. Make a comment of
> this and enable preemption, this fixes the lockdep splat that happened
> when using this feature.
>
> Signed-off-by: Josef Bacik <jbacik@fb.com>
Applied to bpf-next with Fixes tag, thanks Josef.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] trace: reenable preemption if we modify the ip
2017-12-16 2:42 [PATCH] trace: reenable preemption if we modify the ip Josef Bacik
2017-12-17 19:49 ` Daniel Borkmann
@ 2017-12-18 7:29 ` Masami Hiramatsu
1 sibling, 0 replies; 3+ messages in thread
From: Masami Hiramatsu @ 2017-12-18 7:29 UTC (permalink / raw)
To: Josef Bacik; +Cc: netdev, ast, daniel, darrick.wong, linux-kernel, Josef Bacik
On Fri, 15 Dec 2017 21:42:57 -0500
Josef Bacik <josef@toxicpanda.com> wrote:
> From: Josef Bacik <jbacik@fb.com>
>
> Things got moved around between the original bpf_override_return patches
> and the final version, and now the ftrace kprobe dispatcher assumes if
> you modified the ip that you also enabled preemption. Make a comment of
> this and enable preemption, this fixes the lockdep splat that happened
> when using this feature.
>
> Signed-off-by: Josef Bacik <jbacik@fb.com>
> ---
> kernel/trace/trace_kprobe.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 5db849809a56..91f4b57dab82 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1322,8 +1322,15 @@ static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs)
> if (tk->tp.flags & TP_FLAG_TRACE)
> kprobe_trace_func(tk, regs);
> #ifdef CONFIG_PERF_EVENTS
> - if (tk->tp.flags & TP_FLAG_PROFILE)
> + if (tk->tp.flags & TP_FLAG_PROFILE) {
> ret = kprobe_perf_func(tk, regs);
> + /*
> + * The ftrace kprobe handler leaves it up to us to re-enable
> + * preemption here before returning if we've modified the ip.
> + */
> + if (ret)
> + preempt_enable_no_resched();
Where is reset_current_kprobe()?
Since kprobes still expects this modification is used by jprobes,
we need to call it in caller-side.
Thank you,
> + }
> #endif
> return ret;
> }
> --
> 2.7.5
>
--
Masami Hiramatsu <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
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