sparc64: Fix several bugs in quad floating point emulation.

UltraSPARC-T2 and later do not use the fp_exception_other trap and do
not set the floating point trap type field in the %fsr at all when you
try to execute an unimplemented FPU operation.

Instead, it uses the illegal_instruction trap and it leaves the
floating point trap type field clear.

So we should not validate the %fsr trap type field when do_mathemu()
is invoked from the illegal instruction handler.

Also, the floating point trap type field is 3 bits, not 4 bits.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c
index c72fdf55e1c1..3b05e6697710 100644
--- a/arch/sparc/kernel/traps_64.c
+++ b/arch/sparc/kernel/traps_64.c
@@ -2054,7 +2054,7 @@ void do_fpieee(struct pt_regs *regs)
 	do_fpe_common(regs);
 }
 
-extern int do_mathemu(struct pt_regs *, struct fpustate *);
+extern int do_mathemu(struct pt_regs *, struct fpustate *, bool);
 
 void do_fpother(struct pt_regs *regs)
 {
@@ -2068,7 +2068,7 @@ void do_fpother(struct pt_regs *regs)
 	switch ((current_thread_info()->xfsr[0] & 0x1c000)) {
 	case (2 << 14): /* unfinished_FPop */
 	case (3 << 14): /* unimplemented_FPop */
-		ret = do_mathemu(regs, f);
+		ret = do_mathemu(regs, f, false);
 		break;
 	}
 	if (ret)
@@ -2308,10 +2308,12 @@ void do_illegal_instruction(struct pt_regs *regs)
 			} else {
 				struct fpustate *f = FPUSTATE;
 
-				/* XXX maybe verify XFSR bits like
-				 * XXX do_fpother() does?
+				/* On UltraSPARC T2 and later, FPU insns which
+				 * are not implemented in HW signal an illegal
+				 * instruction trap and do not set the FP Trap
+				 * Trap in the %fsr to unimplemented_FPop.
 				 */
-				if (do_mathemu(regs, f))
+				if (do_mathemu(regs, f, true))
 					return;
 			}
 		}