[PATCH] Fix string emulation for 32-bit process on ppc64

[James Yang]

String instruction emulation would erroneously result in a segfault if
the upper bits of the EA are set and is so high that it fails access
check.  Truncate the EA to 32 bits if the process is 32-bit.

Signed-off-by: James Yang <James.Yang at freescale.com>
---
 arch/powerpc/kernel/traps.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index dce1bea..c72e7e9 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -840,6 +840,10 @@ static int emulate_string_inst(struct pt_regs *regs, u32 instword)
 		u8 val;
 		u32 shift = 8 * (3 - (pos & 0x3));
 
+		/* if process is 32-bit, clear upper 32 bits of EA */
+		if ((regs->msr & MSR_64BIT) == 0)
+			EA &= 0xFFFFFFFF;
+
 		switch ((instword & PPC_INST_STRING_MASK)) {
 			case PPC_INST_LSWX:
 			case PPC_INST_LSWI:
-- 
1.7.0.4