[PATCH] riscv: kprobes/ftrace: Add recursion protection to the ftrace callback
Palmer Dabbelt
palmer at dabbelt.com
Mon Apr 12 02:09:07 BST 2021
On Mon, 29 Mar 2021 11:14:40 PDT (-0700), jszhang3 at mail.ustc.edu.cn wrote:
> From: Jisheng Zhang <jszhang at kernel.org>
>
> 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 <jszhang at kernel.org>
> ---
> 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.
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