linux-kernel - [PATCH] MIPS: head: Reorder instructions missing a delay slot

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Message-Id: <20170627191109.28917-1-karl.beldan+oss@gmail.com>
Date:   Tue, 27 Jun 2017 19:11:09 +0000
From:   Karl Beldan <karl.beldan@...il.com>
To:     linux-mips@...ux-mips.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] MIPS: head: Reorder instructions missing a delay slot

In this sequence the 'move' is assumed in the delay slot of the 'beq',
but head.S is in reorder mode and the former gets pushed one 'nop'
farther by the assembler.

The corrected behavior made booting with an UHI supplied dtb erratic.

Fixes: 15f37e158892 ("MIPS: store the appended dtb address in a variable")
Cc: <stable@...r.kernel.org>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Jonas Gorski <jogo@...nwrt.org>
Signed-off-by: Karl Beldan <karl.beldan+oss@...il.com>
---
 arch/mips/kernel/head.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/head.S b/arch/mips/kernel/head.S
index cf05220..d1bb506 100644
--- a/arch/mips/kernel/head.S
+++ b/arch/mips/kernel/head.S
@@ -106,8 +106,8 @@ NESTED(kernel_entry, 16, sp)			# kernel entry point
 	beq		t0, t1, dtb_found
 #endif
 	li		t1, -2
-	beq		a0, t1, dtb_found
 	move		t2, a1
+	beq		a0, t1, dtb_found
 
 	li		t2, 0
 dtb_found:
-- 
2.10.1