linux-kernel - [PATCH 4.4 012/312] MIPS: smp-cps: Stop printing EJTAG exceptions to UART

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Date:   Fri,  8 May 2020 14:30:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paul Burton <paul.burton@...tec.com>,
        linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH 4.4 012/312] MIPS: smp-cps: Stop printing EJTAG exceptions to UART

From: Paul Burton <paul.burton@...tec.com>

commit 6609ccdc852f7bfbfa54300dd5b3cd89eb4ced6f upstream.

When CONFIG_MIPS_CPS_NS16550 is enabled, some register state is dumped
to the UART when an exception is taken via the BEV on secondary cores.
EJTAG exceptions are architecturally expected to be handled by the BEV
even when Status.BEV is 0. This effectively means that if userland
executes an sdbbp instruction on a secondary core then the kernel dumps
register state to the UART even though the exception is perfectly normal
& expected. Prevent this by simply not dumping information to the UART
for EJTAG exceptions.

Fixes: 609cf6f2291a ("MIPS: CPS: Early debug using an ns16550-compatible UART")
Signed-off-by: Paul Burton <paul.burton@...tec.com>
Cc: linux-mips@...ux-mips.org
Cc: linux-kernel@...r.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12341/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/kernel/cps-vec.S |    1 -
 1 file changed, 1 deletion(-)

--- a/arch/mips/kernel/cps-vec.S
+++ b/arch/mips/kernel/cps-vec.S
@@ -245,7 +245,6 @@ LEAF(excep_intex)

 .org 0x480
 LEAF(excep_ejtag)
-	DUMP_EXCEP("EJTAG")
 	PTR_LA	k0, ejtag_debug_handler
 	jr	k0
 	 nop