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

[Jisheng Zhang <jszhang3@mail.ustc.edu.cn>]

From: Jisheng Zhang <jszhang@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@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);
 
-- 
2.31.0