Merge tag 'v3.10.108' into update

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / arch / mips / math-emu / cp1emu.c

diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c
index 3d492a823a55ede158b7dbe13ecdd3c4b2e9005c..dbddc9ccf2705b057b98dc4092e667fafaafe158 100644 (file)
--- a/arch/mips/math-emu/cp1emu.c
+++ b/arch/mips/math-emu/cp1emu.c
@@ -2002,6 +2002,35 @@ static int fpu_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
        return 0;
 }
 
+/*
+ * Emulate FPU instructions.
+ *
+ * If we use FPU hardware, then we have been typically called to handle
+ * an unimplemented operation, such as where an operand is a NaN or
+ * denormalized.  In that case exit the emulation loop after a single
+ * iteration so as to let hardware execute any subsequent instructions.
+ *
+ * If we have no FPU hardware or it has been disabled, then continue
+ * emulating floating-point instructions until one of these conditions
+ * has occurred:
+ *
+ * - a non-FPU instruction has been encountered,
+ *
+ * - an attempt to emulate has ended with a signal,
+ *
+ * - the ISA mode has been switched.
+ *
+ * We need to terminate the emulation loop if we got switched to the
+ * MIPS16 mode, whether supported or not, so that we do not attempt
+ * to emulate a MIPS16 instruction as a regular MIPS FPU instruction.
+ * Similarly if we got switched to the microMIPS mode and only the
+ * regular MIPS mode is supported, so that we do not attempt to emulate
+ * a microMIPS instruction as a regular MIPS FPU instruction.  Or if
+ * we got switched to the regular MIPS mode and only the microMIPS mode
+ * is supported, so that we do not attempt to emulate a regular MIPS
+ * instruction that should cause an Address Error exception instead.
+ * For simplicity we always terminate upon an ISA mode switch.
+ */
 int fpu_emulator_cop1Handler(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
        int has_fpu, void *__user *fault_addr)
 {
@@ -2093,6 +2122,15 @@ int fpu_emulator_cop1Handler(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
                        break;
                if (sig)
                        break;
+               /*
+                * We have to check for the ISA bit explicitly here,
+                * because `get_isa16_mode' may return 0 if support
+                * for code compression has been globally disabled,
+                * or otherwise we may produce the wrong signal or
+                * even proceed successfully where we must not.
+                */
+               if ((xcp->cp0_epc ^ prevepc) & 0x1)
+                       break;
 
                cond_resched();
        } while (xcp->cp0_epc > prevepc);