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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Vincent Chen <vincent.chen@sifive.com>,
        Christoph Hellwig <hch@lst.de>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.3 054/163] riscv: avoid kernel hangs when trapped in BUG()
Date:   Mon,  4 Nov 2019 22:44:04 +0100
Message-Id: <20191104212144.063503330@linuxfoundation.org>
In-Reply-To: <20191104212140.046021995@linuxfoundation.org>
References: <20191104212140.046021995@linuxfoundation.org>
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From: Vincent Chen <vincent.chen@sifive.com>

[ Upstream commit 8b04825ed205da38754f86f4c07ea8600d8c2a65 ]

When the CONFIG_GENERIC_BUG is disabled by disabling CONFIG_BUG, if a
kernel thread is trapped by BUG(), the whole system will be in the
loop that infinitely handles the ebreak exception instead of entering the
die function. To fix this problem, the do_trap_break() will always call
the die() to deal with the break exception as the type of break is
BUG_TRAP_TYPE_BUG.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/riscv/kernel/traps.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 424eb72d56b10..055a937aca70a 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -124,23 +124,23 @@ static inline unsigned long get_break_insn_length(unsigned long pc)
 
 asmlinkage void do_trap_break(struct pt_regs *regs)
 {
-#ifdef CONFIG_GENERIC_BUG
 	if (!user_mode(regs)) {
 		enum bug_trap_type type;
 
 		type = report_bug(regs->sepc, regs);
 		switch (type) {
+#ifdef CONFIG_GENERIC_BUG
 		case BUG_TRAP_TYPE_NONE:
 			break;
 		case BUG_TRAP_TYPE_WARN:
 			regs->sepc += get_break_insn_length(regs->sepc);
 			break;
 		case BUG_TRAP_TYPE_BUG:
+#endif /* CONFIG_GENERIC_BUG */
+		default:
 			die(regs, "Kernel BUG");
 		}
 	}
-#endif /* CONFIG_GENERIC_BUG */
-
 	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs->sepc));
 }
 
-- 
2.20.1