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

[Jisheng Zhang]

From: Jisheng Zhang <jszh...@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 <jszh...@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