[MIPS] FPU ownership management & preemption fixes

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 37 insertions, 47 deletions

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 18f56a9dbcfa..7d76a85422b2 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -610,16 +610,6 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
 	if (fcr31 & FPU_CSR_UNI_X) {
 		int sig;
 
-		preempt_disable();
-
-#ifdef CONFIG_PREEMPT
-		if (!is_fpu_owner()) {
-			/* We might lose fpu before disabling preempt... */
-			own_fpu();
-			BUG_ON(!used_math());
-			restore_fp(current);
-		}
-#endif
 		/*
 		 * Unimplemented operation exception.  If we've got the full
 		 * software emulator on-board, let's use it...
@@ -630,18 +620,12 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
 		 * register operands before invoking the emulator, which seems
 		 * a bit extreme for what should be an infrequent event.
 		 */
-		save_fp(current);
 		/* Ensure 'resume' not overwrite saved fp context again. */
-		lose_fpu();
-
-		preempt_enable();
+		lose_fpu(1);
 
 		/* Run the emulator */
 		sig = fpu_emulator_cop1Handler (regs, &current->thread.fpu, 1);
 
-		preempt_disable();
-
-		own_fpu();	/* Using the FPU again.  */
 		/*
 		 * We can't allow the emulated instruction to leave any of
 		 * the cause bit set in $fcr31.
@@ -649,9 +633,7 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
 		current->thread.fpu.fcr31 &= ~FPU_CSR_ALL_X;
 
 		/* Restore the hardware register state */
-		restore_fp(current);
-
-		preempt_enable();
+		own_fpu(1);	/* Using the FPU again.  */
 
 		/* If something went wrong, signal */
 		if (sig)
@@ -775,12 +757,11 @@ asmlinkage void do_cpu(struct pt_regs *regs)
 {
 	unsigned int cpid;
 
-	die_if_kernel("do_cpu invoked from kernel context!", regs);
-
 	cpid = (regs->cp0_cause >> CAUSEB_CE) & 3;
 
 	switch (cpid) {
 	case 0:
+		die_if_kernel("do_cpu invoked from kernel context!", regs);
 		if (!cpu_has_llsc)
 			if (!simulate_llsc(regs))
 				return;
@@ -791,21 +772,30 @@ asmlinkage void do_cpu(struct pt_regs *regs)
 		break;
 
 	case 1:
-		preempt_disable();
-
-		own_fpu();
-		if (used_math()) {	/* Using the FPU again.  */
-			restore_fp(current);
-		} else {			/* First time FPU user.  */
+		if (!test_thread_flag(TIF_ALLOW_FP_IN_KERNEL))
+			die_if_kernel("do_cpu invoked from kernel context!",
+				      regs);
+		if (used_math())	/* Using the FPU again.  */
+			own_fpu(1);
+		else {			/* First time FPU user.  */
 			init_fpu();
 			set_used_math();
 		}
 
-		if (cpu_has_fpu) {
-			preempt_enable();
+		if (raw_cpu_has_fpu) {
+			if (test_thread_flag(TIF_ALLOW_FP_IN_KERNEL)) {
+				local_irq_disable();
+				if (cpu_has_fpu)
+					regs->cp0_status |= ST0_CU1;
+				/*
+				 * We must return without enabling
+				 * interrupts to ensure keep FPU
+				 * ownership until resume.
+				 */
+				return;
+			}
 		} else {
 			int sig;
-			preempt_enable();
 			sig = fpu_emulator_cop1Handler(regs,
 						&current->thread.fpu, 0);
 			if (sig)
@@ -1259,26 +1249,26 @@ static inline void mips_srs_init(void)
 /*
  * This is used by native signal handling
  */
-asmlinkage int (*save_fp_context)(struct sigcontext *sc);
-asmlinkage int (*restore_fp_context)(struct sigcontext *sc);
+asmlinkage int (*save_fp_context)(struct sigcontext __user *sc);
+asmlinkage int (*restore_fp_context)(struct sigcontext __user *sc);
 
-extern asmlinkage int _save_fp_context(struct sigcontext *sc);
-extern asmlinkage int _restore_fp_context(struct sigcontext *sc);
+extern asmlinkage int _save_fp_context(struct sigcontext __user *sc);
+extern asmlinkage int _restore_fp_context(struct sigcontext __user *sc);
 
-extern asmlinkage int fpu_emulator_save_context(struct sigcontext *sc);
-extern asmlinkage int fpu_emulator_restore_context(struct sigcontext *sc);
+extern asmlinkage int fpu_emulator_save_context(struct sigcontext __user *sc);
+extern asmlinkage int fpu_emulator_restore_context(struct sigcontext __user *sc);
 
 #ifdef CONFIG_SMP
-static int smp_save_fp_context(struct sigcontext *sc)
+static int smp_save_fp_context(struct sigcontext __user *sc)
 {
-	return cpu_has_fpu
+	return raw_cpu_has_fpu
 	       ? _save_fp_context(sc)
 	       : fpu_emulator_save_context(sc);
 }
 
-static int smp_restore_fp_context(struct sigcontext *sc)
+static int smp_restore_fp_context(struct sigcontext __user *sc)
 {
-	return cpu_has_fpu
+	return raw_cpu_has_fpu
 	       ? _restore_fp_context(sc)
 	       : fpu_emulator_restore_context(sc);
 }
@@ -1306,14 +1296,14 @@ static inline void signal_init(void)
 /*
  * This is used by 32-bit signal stuff on the 64-bit kernel
  */
-asmlinkage int (*save_fp_context32)(struct sigcontext32 *sc);
-asmlinkage int (*restore_fp_context32)(struct sigcontext32 *sc);
+asmlinkage int (*save_fp_context32)(struct sigcontext32 __user *sc);
+asmlinkage int (*restore_fp_context32)(struct sigcontext32 __user *sc);
 
-extern asmlinkage int _save_fp_context32(struct sigcontext32 *sc);
-extern asmlinkage int _restore_fp_context32(struct sigcontext32 *sc);
+extern asmlinkage int _save_fp_context32(struct sigcontext32 __user *sc);
+extern asmlinkage int _restore_fp_context32(struct sigcontext32 __user *sc);
 
-extern asmlinkage int fpu_emulator_save_context32(struct sigcontext32 *sc);
-extern asmlinkage int fpu_emulator_restore_context32(struct sigcontext32 *sc);
+extern asmlinkage int fpu_emulator_save_context32(struct sigcontext32 __user *sc);
+extern asmlinkage int fpu_emulator_restore_context32(struct sigcontext32 __user *sc);
 
 static inline void signal32_init(void)
 {