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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>
Gabor Juhos 12 years ago
parent
commit
14fdd1a8bf
2 changed files with 3 additions and 0 deletions
  1. 2 0
      arch/mips/cpu/mips32/start.S
  2. 1 0
      arch/mips/cpu/mips64/start.S

+ 2 - 0
arch/mips/cpu/mips32/start.S

@@ -380,6 +380,8 @@ in_ram:
 	/* Exception handlers */
 romReserved:
 	b	romReserved
+	 nop
 
 romExcHandle:
 	b	romExcHandle
+	 nop

+ 1 - 0
arch/mips/cpu/mips64/start.S

@@ -259,3 +259,4 @@ in_ram:
 	/* Exception handlers */
 romReserved:
 	b	romReserved
+	 nop