linux-kernel - [PATCH] LoongArch: Enhance robust of kprobe

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Message-ID: <20250408092756.22339-1-yangtiezhu@loongson.cn>
Date: Tue,  8 Apr 2025 17:27:56 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH] LoongArch: Enhance robust of kprobe

Currently, interrupts need to be disabled before single-step mode is set,
it requires that the CSR_PRMD_PIE must be cleared in save_local_irqflag()
which is called by setup_singlestep(), this is reasonable.

But in the first kprobe breakpoint exception, if the irq is enabled at the
beginning of do_bp(), it will not be disabled at the end of do_bp() due to
the CSR_PRMD_PIE has been cleared in save_local_irqflag(). For this case,
it may corrupt exception context when restoring exception after do_bp() in
handle_bp(), this is not reasonable.

Based on the above analysis, in order to make sure the irq is disabled at
the end of do_bp() for the first kprobe breakpoint exception, it is proper
to disable irq first before clearing CSR_PRMD_PIE in save_local_irqflag().

Fixes: 6d4cc40fb5f5 ("LoongArch: Add kprobes support")
Co-developed-by: Tianyang Zhang <zhangtianyang@...ngson.cn>
Signed-off-by: Tianyang Zhang <zhangtianyang@...ngson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 arch/loongarch/kernel/kprobes.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/loongarch/kernel/kprobes.c b/arch/loongarch/kernel/kprobes.c
index 8ba391cfabb0..6eab97636e6b 100644
--- a/arch/loongarch/kernel/kprobes.c
+++ b/arch/loongarch/kernel/kprobes.c
@@ -113,6 +113,7 @@ NOKPROBE_SYMBOL(set_current_kprobe);
 static void save_local_irqflag(struct kprobe_ctlblk *kcb,
 			       struct pt_regs *regs)
 {
+	local_irq_disable();
 	kcb->saved_status = regs->csr_prmd;
 	regs->csr_prmd &= ~CSR_PRMD_PIE;
 }
-- 
2.42.0