2021-03-29 18:22:01

by Jisheng Zhang

Subject: [PATCH] riscv: kprobes/ftrace: Add recursion protection to the ftrace callback

From: Jisheng Zhang <[email protected]>

Currently, the riscv's kprobes(powerred by ftrace) handler is
preemptible. Futher check indicates we miss something similar as the
commit c536aa1c5b17 ("kprobes/ftrace: Add recursion protection to the
ftrace callback"), so do similar modifications as the commit does.

Fixes: 829adda597fe ("riscv: Add KPROBES_ON_FTRACE supported")
Signed-off-by: Jisheng Zhang <[email protected]>
---
arch/riscv/kernel/probes/ftrace.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/probes/ftrace.c b/arch/riscv/kernel/probes/ftrace.c
index 17ca5e923bb0..aab85a82f419 100644
--- a/arch/riscv/kernel/probes/ftrace.c
+++ b/arch/riscv/kernel/probes/ftrace.c
@@ -9,10 +9,16 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
struct kprobe *p;
struct pt_regs *regs;
struct kprobe_ctlblk *kcb;
+ int bit;

+ bit = ftrace_test_recursion_trylock(ip, parent_ip);
+ if (bit < 0)
+ return;
+
+ preempt_disable_notrace();
p = get_kprobe((kprobe_opcode_t *)ip);
if (unlikely(!p) || kprobe_disabled(p))
- return;
+ goto out;

regs = ftrace_get_regs(fregs);
kcb = get_kprobe_ctlblk();
@@ -45,6 +51,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
*/
__this_cpu_write(current_kprobe, NULL);
}
+out:
+ preempt_enable_notrace();
+ ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);

--
2.31.0

2021-03-30 19:41:55

by Steven Rostedt

Subject: Re: [PATCH] riscv: kprobes/ftrace: Add recursion protection to the ftrace callback

On Tue, 30 Mar 2021 02:14:40 +0800
Jisheng Zhang <[email protected]> wrote:

> From: Jisheng Zhang <[email protected]>
>
> Currently, the riscv's kprobes(powerred by ftrace) handler is
> preemptible. Futher check indicates we miss something similar as the
> commit c536aa1c5b17 ("kprobes/ftrace: Add recursion protection to the
> ftrace callback"), so do similar modifications as the commit does.
>
> Fixes: 829adda597fe ("riscv: Add KPROBES_ON_FTRACE supported")
> Signed-off-by: Jisheng Zhang <[email protected]>

Looks fine to me.

Reviewed-by: Steven Rostedt (VMware) <[email protected]>

-- Steve

2021-04-12 01:11:39

by Palmer Dabbelt

Subject: Re: [PATCH] riscv: kprobes/ftrace: Add recursion protection to the ftrace callback

On Mon, 29 Mar 2021 11:14:40 PDT (-0700), [email protected] wrote:
> From: Jisheng Zhang <[email protected]>
>
> Currently, the riscv's kprobes(powerred by ftrace) handler is
> preemptible. Futher check indicates we miss something similar as the
> commit c536aa1c5b17 ("kprobes/ftrace: Add recursion protection to the
> ftrace callback"), so do similar modifications as the commit does.
>
> Fixes: 829adda597fe ("riscv: Add KPROBES_ON_FTRACE supported")
> Signed-off-by: Jisheng Zhang <[email protected]>
> ---
> arch/riscv/kernel/probes/ftrace.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/probes/ftrace.c b/arch/riscv/kernel/probes/ftrace.c
> index 17ca5e923bb0..aab85a82f419 100644
> --- a/arch/riscv/kernel/probes/ftrace.c
> +++ b/arch/riscv/kernel/probes/ftrace.c
> @@ -9,10 +9,16 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
> struct kprobe *p;
> struct pt_regs *regs;
> struct kprobe_ctlblk *kcb;
> + int bit;
>
> + bit = ftrace_test_recursion_trylock(ip, parent_ip);
> + if (bit < 0)
> + return;
> +
> + preempt_disable_notrace();
> p = get_kprobe((kprobe_opcode_t *)ip);
> if (unlikely(!p) || kprobe_disabled(p))
> - return;
> + goto out;
>
> regs = ftrace_get_regs(fregs);
> kcb = get_kprobe_ctlblk();
> @@ -45,6 +51,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
> */
> __this_cpu_write(current_kprobe, NULL);
> }
> +out:
> + preempt_enable_notrace();
> + ftrace_test_recursion_unlock(bit);
> }
> NOKPROBE_SYMBOL(kprobe_ftrace_handler);

Thanks, this is on fixes.