1 files changed, 245 insertions, 47 deletions

diff --git a/arch/mips/include/asm/fpu.h b/arch/mips/include/asm/fpu.h
index d088e5db4903..bc5ac9887d09 100644
--- a/arch/mips/include/asm/fpu.h
+++ b/arch/mips/include/asm/fpu.h
@@ -1,62 +1,107 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
 /*
  * Copyright (C) 2002 MontaVista Software Inc.
  * Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by the
- * Free Software Foundation;  either version 2 of the  License, or (at your
- * option) any later version.
  */
 #ifndef _ASM_FPU_H
 #define _ASM_FPU_H
 
 #include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/ptrace.h>
 #include <linux/thread_info.h>
 #include <linux/bitops.h>
 
 #include <asm/mipsregs.h>
 #include <asm/cpu.h>
 #include <asm/cpu-features.h>
+#include <asm/fpu_emulator.h>
 #include <asm/hazards.h>
+#include <asm/ptrace.h>
 #include <asm/processor.h>
 #include <asm/current.h>
+#include <asm/msa.h>
 
 #ifdef CONFIG_MIPS_MT_FPAFF
 #include <asm/mips_mt.h>
 #endif
 
-struct sigcontext;
-struct sigcontext32;
+/*
+ * This enum specifies a mode in which we want the FPU to operate, for cores
+ * which implement the Status.FR bit. Note that the bottom bit of the value
+ * purposefully matches the desired value of the Status.FR bit.
+ */
+enum fpu_mode {
+	FPU_32BIT = 0,		/* FR = 0 */
+	FPU_64BIT,		/* FR = 1, FRE = 0 */
+	FPU_AS_IS,
+	FPU_HYBRID,		/* FR = 1, FRE = 1 */
+
+#define FPU_FR_MASK		0x1
+};
+
+#ifdef CONFIG_MIPS_FP_SUPPORT
 
-extern void fpu_emulator_init_fpu(void);
-extern void _init_fpu(void);
 extern void _save_fp(struct task_struct *);
 extern void _restore_fp(struct task_struct *);
 
-#define __enable_fpu()							\
-do {									\
-	set_c0_status(ST0_CU1);						\
-	enable_fpu_hazard();						\
-} while (0)
-
 #define __disable_fpu()							\
 do {									\
 	clear_c0_status(ST0_CU1);					\
 	disable_fpu_hazard();						\
 } while (0)
 
-#define enable_fpu()							\
-do {									\
-	if (cpu_has_fpu)						\
-		__enable_fpu();						\
-} while (0)
+static inline int __enable_fpu(enum fpu_mode mode)
+{
+	int fr;
 
-#define disable_fpu()							\
-do {									\
-	if (cpu_has_fpu)						\
-		__disable_fpu();					\
-} while (0)
+	switch (mode) {
+	case FPU_AS_IS:
+		/* just enable the FPU in its current mode */
+		set_c0_status(ST0_CU1);
+		enable_fpu_hazard();
+		return 0;
+
+	case FPU_HYBRID:
+		if (!cpu_has_fre)
+			return SIGFPE;
+
+		/* set FRE */
+		set_c0_config5(MIPS_CONF5_FRE);
+		goto fr_common;
+
+	case FPU_64BIT:
+#if !(defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR5) || \
+      defined(CONFIG_CPU_MIPSR6) || defined(CONFIG_64BIT))
+		/* we only have a 32-bit FPU */
+		return SIGFPE;
+#endif
+		/* fallthrough */
+	case FPU_32BIT:
+		if (cpu_has_fre) {
+			/* clear FRE */
+			clear_c0_config5(MIPS_CONF5_FRE);
+		}
+fr_common:
+		/* set CU1 & change FR appropriately */
+		fr = (int)mode & FPU_FR_MASK;
+		change_c0_status(ST0_CU1 | ST0_FR, ST0_CU1 | (fr ? ST0_FR : 0));
+		enable_fpu_hazard();
+
+		/* check FR has the desired value */
+		if (!!(read_c0_status() & ST0_FR) == !!fr)
+			return 0;
 
+		/* unsupported FR value */
+		__disable_fpu();
+		return SIGFPE;
+
+	default:
+		BUG();
+	}
+
+	return SIGFPE;
+}
 
 #define clear_fpu_owner()	clear_thread_flag(TIF_USEDFPU)
 
@@ -70,54 +115,130 @@ static inline int is_fpu_owner(void)
 	return cpu_has_fpu && __is_fpu_owner();
 }
 
-static inline void __own_fpu(void)
+static inline int __own_fpu(void)
 {
-	__enable_fpu();
+	enum fpu_mode mode;
+	int ret;
+
+	if (test_thread_flag(TIF_HYBRID_FPREGS))
+		mode = FPU_HYBRID;
+	else
+		mode = !test_thread_flag(TIF_32BIT_FPREGS);
+
+	ret = __enable_fpu(mode);
+	if (ret)
+		return ret;
+
+	if (current->thread.fpu.fcr31 & FPU_CSR_NAN2008) {
+		if (!cpu_has_nan_2008) {
+			ret = SIGFPE;
+			goto failed;
+		}
+	} else {
+		if (!cpu_has_nan_legacy) {
+			ret = SIGFPE;
+			goto failed;
+		}
+	}
+
 	KSTK_STATUS(current) |= ST0_CU1;
+	if (mode == FPU_64BIT || mode == FPU_HYBRID)
+		KSTK_STATUS(current) |= ST0_FR;
+	else /* mode == FPU_32BIT */
+		KSTK_STATUS(current) &= ~ST0_FR;
+
 	set_thread_flag(TIF_USEDFPU);
+	return 0;
+failed:
+	__disable_fpu();
+	return ret;
 }
 
-static inline void own_fpu_inatomic(int restore)
+static inline int own_fpu_inatomic(int restore)
 {
+	int ret = 0;
+
 	if (cpu_has_fpu && !__is_fpu_owner()) {
-		__own_fpu();
-		if (restore)
+		ret = __own_fpu();
+		if (restore && !ret)
 			_restore_fp(current);
 	}
+	return ret;
 }
 
-static inline void own_fpu(int restore)
+static inline int own_fpu(int restore)
 {
+	int ret;
+
 	preempt_disable();
-	own_fpu_inatomic(restore);
+	ret = own_fpu_inatomic(restore);
 	preempt_enable();
+	return ret;
 }
 
-static inline void lose_fpu(int save)
+static inline void lose_fpu_inatomic(int save, struct task_struct *tsk)
 {
-	preempt_disable();
-	if (is_fpu_owner()) {
+	if (is_msa_enabled()) {
+		if (save) {
+			save_msa(tsk);
+			tsk->thread.fpu.fcr31 =
+					read_32bit_cp1_register(CP1_STATUS);
+		}
+		disable_msa();
+		clear_tsk_thread_flag(tsk, TIF_USEDMSA);
+		__disable_fpu();
+	} else if (is_fpu_owner()) {
 		if (save)
-			_save_fp(current);
-		KSTK_STATUS(current) &= ~ST0_CU1;
-		clear_thread_flag(TIF_USEDFPU);
+			_save_fp(tsk);
 		__disable_fpu();
+	} else {
+		/* FPU should not have been left enabled with no owner */
+		WARN(read_c0_status() & ST0_CU1,
+		     "Orphaned FPU left enabled");
 	}
-	preempt_enable();
+	KSTK_STATUS(tsk) &= ~ST0_CU1;
+	clear_tsk_thread_flag(tsk, TIF_USEDFPU);
 }
 
-static inline void init_fpu(void)
+static inline void lose_fpu(int save)
 {
 	preempt_disable();
-	if (cpu_has_fpu) {
-		__own_fpu();
-		_init_fpu();
-	} else {
-		fpu_emulator_init_fpu();
-	}
+	lose_fpu_inatomic(save, current);
 	preempt_enable();
 }
 
+/**
+ * init_fp_ctx() - Initialize task FP context
+ * @target: The task whose FP context should be initialized.
+ *
+ * Initializes the FP context of the target task to sane default values if that
+ * target task does not already have valid FP context. Once the context has
+ * been initialized, the task will be marked as having used FP & thus having
+ * valid FP context.
+ *
+ * Returns: true if context is initialized, else false.
+ */
+static inline bool init_fp_ctx(struct task_struct *target)
+{
+	/* If FP has been used then the target already has context */
+	if (tsk_used_math(target))
+		return false;
+
+	/* Begin with data registers set to all 1s... */
+	memset(&target->thread.fpu.fpr, ~0, sizeof(target->thread.fpu.fpr));
+
+	/* FCSR has been preset by `mips_set_personality_nan'.  */
+
+	/*
+	 * Record that the target has "used" math, such that the context
+	 * just initialised, and any modifications made by the caller,
+	 * aren't discarded.
+	 */
+	set_stopped_child_used_math(target);
+
+	return true;
+}
+
 static inline void save_fp(struct task_struct *tsk)
 {
 	if (cpu_has_fpu)
@@ -130,7 +251,7 @@ static inline void restore_fp(struct task_struct *tsk)
 		_restore_fp(tsk);
 }
 
-static inline fpureg_t *get_fpu_regs(struct task_struct *tsk)
+static inline union fpureg *get_fpu_regs(struct task_struct *tsk)
 {
 	if (tsk == current) {
 		preempt_disable();
@@ -142,4 +263,81 @@ static inline fpureg_t *get_fpu_regs(struct task_struct *tsk)
 	return tsk->thread.fpu.fpr;
 }
 
+#else /* !CONFIG_MIPS_FP_SUPPORT */
+
+/*
+ * When FP support is disabled we provide only a minimal set of stub functions
+ * to avoid callers needing to care too much about CONFIG_MIPS_FP_SUPPORT.
+ */
+
+static inline int __enable_fpu(enum fpu_mode mode)
+{
+	return SIGILL;
+}
+
+static inline void __disable_fpu(void)
+{
+	/* no-op */
+}
+
+
+static inline int is_fpu_owner(void)
+{
+	return 0;
+}
+
+static inline void clear_fpu_owner(void)
+{
+	/* no-op */
+}
+
+static inline int own_fpu_inatomic(int restore)
+{
+	return SIGILL;
+}
+
+static inline int own_fpu(int restore)
+{
+	return SIGILL;
+}
+
+static inline void lose_fpu_inatomic(int save, struct task_struct *tsk)
+{
+	/* no-op */
+}
+
+static inline void lose_fpu(int save)
+{
+	/* no-op */
+}
+
+static inline bool init_fp_ctx(struct task_struct *target)
+{
+	return false;
+}
+
+/*
+ * The following functions should only be called in paths where we know that FP
+ * support is enabled, typically a path where own_fpu() or __enable_fpu() have
+ * returned successfully. When CONFIG_MIPS_FP_SUPPORT=n it is known at compile
+ * time that this should never happen, so calls to these functions should be
+ * optimized away & never actually be emitted.
+ */
+
+extern void save_fp(struct task_struct *tsk)
+	__compiletime_error("save_fp() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
+
+extern void _save_fp(struct task_struct *)
+	__compiletime_error("_save_fp() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
+
+extern void restore_fp(struct task_struct *tsk)
+	__compiletime_error("restore_fp() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
+
+extern void _restore_fp(struct task_struct *)
+	__compiletime_error("_restore_fp() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
+
+extern union fpureg *get_fpu_regs(struct task_struct *tsk)
+	__compiletime_error("get_fpu_regs() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
+
+#endif /* !CONFIG_MIPS_FP_SUPPORT */
 #endif /* _ASM_FPU_H */