linux-kernel - [PATCH] arm64: traps: add dump instr before BUG in kernel

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Date:   Wed, 29 Sep 2021 21:29:46 +0800
From:   Chen Lin <chen45464546@....com>
To:     catalin.marinas@....com
Cc:     will@...nel.org, mark.rutland@....com, joey.gouly@....com,
        maz@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Chen Lin <chen.lin5@....com.cn>
Subject: [PATCH] arm64: traps: add dump instr before BUG in kernel

From: Chen Lin <chen.lin5@....com.cn>

we should dump the real instructions before BUG in kernel mode, and
compare this to the instructions from objdump.

Signed-off-by: Chen Lin <chen.lin5@....com.cn>
---
 arch/arm64/kernel/traps.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index b03e383..621a9dd 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -495,7 +495,12 @@ void do_undefinstr(struct pt_regs *regs)
 	if (call_undef_hook(regs) == 0)
 		return;
 
-	BUG_ON(!user_mode(regs));
+	if (!user_mode(regs)) {
+		pr_emerg("Undef instruction in kernel, dump instr:");
+		dump_kernel_instr(KERN_EMERG, regs);
+		BUG();
+	}
+
 	force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
 }
 NOKPROBE_SYMBOL(do_undefinstr);
-- 
1.7.9.5