From 92b4dc16257fef814ddf1c8d1d2a20f67f67ee4b Mon Sep 17 00:00:00 2001
From: Kumar Gala <galak@freescale.com>
Date: Sat, 28 May 2005 15:52:13 -0700
Subject: [PATCH] [PATCH] ppc32: Simplified load string emulation error
 checking

The error checking for emulation of load string instructions was overly
generous and would cause certain valid forms of the instructions to be
treated as illegal.  We drop the range checking since the architecture
allows this to be boundedly undefined.  Tests on CPUs that support these
instructions appear not do cause illegal instruction traps on range errors
and just allow the execution to occur.

Thanks to Kim Phillips for debugging this and figuring out what real HW was
doing.

Signed-off-by: Kumar Gala <kumar.gala@freescale.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
 arch/ppc/kernel/traps.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/ppc/kernel/traps.c b/arch/ppc/kernel/traps.c
index f8e7e324a173..c65731e8bc65 100644
--- a/arch/ppc/kernel/traps.c
+++ b/arch/ppc/kernel/traps.c
@@ -408,12 +408,7 @@ static int emulate_string_inst(struct pt_regs *regs, u32 instword)
 
 	/* Early out if we are an invalid form of lswx */
 	if ((instword & INST_STRING_MASK) == INST_LSWX)
-		if ((rA >= rT) || (NB_RB >= rT) || (rT == rA) || (rT == NB_RB))
-			return -EINVAL;
-
-	/* Early out if we are an invalid form of lswi */
-	if ((instword & INST_STRING_MASK) == INST_LSWI)
-		if ((rA >= rT) || (rT == rA))
+		if ((rT == rA) || (rT == NB_RB))
 			return -EINVAL;
 
 	EA = (rA == 0) ? 0 : regs->gpr[rA];
-- 
2.30.9