From: Gabor Juhos <juhosg@openwrt.org>
Date: Wed, 16 Jan 2013 03:05:01 +0000 (+0000)
Subject: MIPS: start{, 64}.S: fill branch delay slots with NOP instructions
X-Git-Tag: v2013.04-rc1~136^2~15
X-Git-Url: https://repo.jachan.dev/J-u-boot.git/commitdiff_plain/14fdd1a8bfd97de46042cda6086347b0d66461d4

MIPS: start{, 64}.S: fill branch delay slots with NOP instructions

The romReserved and romExcHandle handlers are
accessed by a branch instruction however the
delay slots of those instructions are not filled.

Because the start.S uses the 'noreorder' directive,
the assembler will not fill the delay slots either,
and leads to the following assembly code:

  0000056c <romReserved>:
   56c:   1000ffff        b       56c <romReserved>

  00000570 <romExcHandle>:
   570:   1000ffff        b       570 <romExcHandle>

In the resulting code, the second branch instruction
is placed into the delay slot of the first branch
instruction, which is not allowed on the MIPS
architecture.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
---

diff --git a/arch/mips/cpu/mips32/start.S b/arch/mips/cpu/mips32/start.S
index 9c1b2f76d09..22a9c1bff5e 100644
--- a/arch/mips/cpu/mips32/start.S
+++ b/arch/mips/cpu/mips32/start.S
@@ -380,6 +380,8 @@ in_ram:
 	/* Exception handlers */
 romReserved:
 	b	romReserved
+	 nop
 
 romExcHandle:
 	b	romExcHandle
+	 nop
diff --git a/arch/mips/cpu/mips64/start.S b/arch/mips/cpu/mips64/start.S
index 2b8d531e73b..bc7e41eed52 100644
--- a/arch/mips/cpu/mips64/start.S
+++ b/arch/mips/cpu/mips64/start.S
@@ -259,3 +259,4 @@ in_ram:
 	/* Exception handlers */
 romReserved:
 	b	romReserved
+	 nop