[POWERPC] Fix handling of stfiwx math emulation

Its legal for the stfiwx instruction to have RA = 0 as part of its
effective address calculation.  This is illegal for all other XE
form instructions.

Add code to compute the proper effective address for stfiwx if
RA = 0 rather than treating it as illegal.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/arch/powerpc/math-emu/math.c b/arch/powerpc/math-emu/math.c
index 69058b2873de..381306bb1590 100644
--- a/arch/powerpc/math-emu/math.c
+++ b/arch/powerpc/math-emu/math.c
@@ -407,11 +407,16 @@ do_mathemu(struct pt_regs *regs)
 
         case XE:
                 idx = (insn >> 16) & 0x1f;
-                if (!idx)
-                        goto illegal;
-
                 op0 = (void *)&current->thread.fpr[(insn >> 21) & 0x1f];
-                op1 = (void *)(regs->gpr[idx] + regs->gpr[(insn >> 11) & 0x1f]);
+                if (!idx) {
+                        if (((insn >> 1) & 0x3ff) == STFIWX)
+                                op1 = (void *)(regs->gpr[(insn >> 11) & 0x1f]);
+                        else
+                                goto illegal;
+                } else {
+                        op1 = (void *)(regs->gpr[idx] + regs->gpr[(insn >> 11) & 0x1f]);
+                }
+
                 break;
 
         case XEU: