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>

2 files changed, 21 insertions, 11 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;
                         }
                 }
diff --git a/arch/sparc/math-emu/math_64.c b/arch/sparc/math-emu/math_64.c
index 2bbe2f28ad23..1704068da928 100644
--- a/arch/sparc/math-emu/math_64.c
+++ b/arch/sparc/math-emu/math_64.c
@@ -163,7 +163,7 @@ typedef union {
         u64 q[2];
 } *argp;
 
-int do_mathemu(struct pt_regs *regs, struct fpustate *f)
+int do_mathemu(struct pt_regs *regs, struct fpustate *f, bool illegal_insn_trap)
 {
         unsigned long pc = regs->tpc;
         unsigned long tstate = regs->tstate;
@@ -218,7 +218,7 @@ int do_mathemu(struct pt_regs *regs, struct fpustate *f)
                         case FSQRTS: {
                                 unsigned long x = current_thread_info()->xfsr[0];
 
-                                x = (x >> 14) & 0xf;
+                                x = (x >> 14) & 0x7;
                                 TYPE(x,1,1,1,1,0,0);
                                 break;
                         }
@@ -226,7 +226,7 @@ int do_mathemu(struct pt_regs *regs, struct fpustate *f)
                         case FSQRTD: {
                                 unsigned long x = current_thread_info()->xfsr[0];
 
-                                x = (x >> 14) & 0xf;
+                                x = (x >> 14) & 0x7;
                                 TYPE(x,2,1,2,1,0,0);
                                 break;
                         }
@@ -357,9 +357,17 @@ int do_mathemu(struct pt_regs *regs, struct fpustate *f)
         if (type) {
                 argp rs1 = NULL, rs2 = NULL, rd = NULL;
                 
-                freg = (current_thread_info()->xfsr[0] >> 14) & 0xf;
-                if (freg != (type >> 9))
-                        goto err;
+                /* Starting with UltraSPARC-T2, the cpu does not set the FP Trap
+                 * Type field in the %fsr to unimplemented_FPop.  Nor does it
+                 * use the fp_exception_other trap.  Instead it signals an
+                 * illegal instruction and leaves the FP trap type field of
+                 * the %fsr unchanged.
+                 */
+                if (!illegal_insn_trap) {
+                        int ftt = (current_thread_info()->xfsr[0] >> 14) & 0x7;
+                        if (ftt != (type >> 9))
+                                goto err;
+                }
                 current_thread_info()->xfsr[0] &= ~0x1c000;
                 freg = ((insn >> 14) & 0x1f);
                 switch (type & 0x3) {