fpu-internal.h

/*
 * Copyright (C) 1994 Linus Torvalds
 *
 * Pentium III FXSR, SSE support
 * General FPU state handling cleanups
 *	Gareth Hughes <gareth@valinux.com>, May 2000
 * x86-64 work by Andi Kleen 2002
 */

#ifndef _FPU_INTERNAL_H
#define _FPU_INTERNAL_H

#include <linux/kernel_stat.h>
#include <linux/regset.h>
#include <linux/compat.h>
#include <linux/slab.h>
#include <asm/asm.h>
#include <asm/cpufeature.h>
#include <asm/processor.h>
#include <asm/sigcontext.h>
#include <asm/user.h>
#include <asm/uaccess.h>
#include <asm/xsave.h>

extern unsigned int sig_xstate_size;
extern void fpu_init(void);

DECLARE_PER_CPU(struct task_struct *, fpu_owner_task);

extern user_regset_active_fn fpregs_active, xfpregs_active;
extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get,
				xstateregs_get;
extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set,
				 xstateregs_set;

/*
 * xstateregs_active == fpregs_active. Please refer to the comment
 * at the definition of fpregs_active.
 */
#define xstateregs_active	fpregs_active

extern struct _fpx_sw_bytes fx_sw_reserved;
#ifdef CONFIG_IA32_EMULATION
extern unsigned int sig_xstate_ia32_size;
extern struct _fpx_sw_bytes fx_sw_reserved_ia32;
struct _fpstate_ia32;
struct _xstate_ia32;
extern int save_i387_xstate_ia32(void __user *buf);
extern int restore_i387_xstate_ia32(void __user *buf);
#endif

#ifdef CONFIG_MATH_EMULATION
extern void finit_soft_fpu(struct i387_soft_struct *soft);
#else
static inline void finit_soft_fpu(struct i387_soft_struct *soft) {}
#endif

static inline int is_ia32_compat_frame(void)
{
	return config_enabled(CONFIG_IA32_EMULATION) &&
	       test_thread_flag(TIF_IA32);
}

static inline int is_ia32_frame(void)
{
	return config_enabled(CONFIG_X86_32) || is_ia32_compat_frame();
}

static inline int is_x32_frame(void)
{
	return config_enabled(CONFIG_X86_X32_ABI) && test_thread_flag(TIF_X32);
}

#define X87_FSW_ES (1 << 7)	/* Exception Summary */

static __always_inline __pure bool use_xsaveopt(void)
{
	return static_cpu_has(X86_FEATURE_XSAVEOPT);
}

static __always_inline __pure bool use_xsave(void)
{
	return static_cpu_has(X86_FEATURE_XSAVE);
}

static __always_inline __pure bool use_fxsr(void)
{
        return static_cpu_has(X86_FEATURE_FXSR);
}

extern void __sanitize_i387_state(struct task_struct *);

static inline void sanitize_i387_state(struct task_struct *tsk)
{
	if (!use_xsaveopt())
		return;
	__sanitize_i387_state(tsk);
}

#define check_insn(insn, output, input...)				\
({									\
	int err;							\
	asm volatile("1:" #insn "\n\t"					\
		     "2:\n"						\
		     ".section .fixup,\"ax\"\n"				\
		     "3:  movl $-1,%[err]\n"				\
		     "    jmp  2b\n"					\
		     ".previous\n"					\
		     _ASM_EXTABLE(1b, 3b)				\
		     : [err] "=r" (err), output				\
		     : "0"(0), input);					\
	err;								\
})

static inline int fsave_user(struct i387_fsave_struct __user *fx)
{
	return check_insn(fnsave %[fx]; fwait,  [fx] "=m" (*fx), "m" (*fx));
}

static inline int fxsave_user(struct i387_fxsave_struct __user *fx)
{
	int err;

	/*
	 * Clear the bytes not touched by the fxsave and reserved
	 * for the SW usage.
	 */
	err = __clear_user(&fx->sw_reserved,
			   sizeof(struct _fpx_sw_bytes));
	if (unlikely(err))
		return -EFAULT;

	if (config_enabled(CONFIG_X86_32))
		return check_insn(fxsave %[fx], [fx] "=m" (*fx), "m" (*fx));
	else if (config_enabled(CONFIG_AS_FXSAVEQ))
		return check_insn(fxsaveq %[fx], [fx] "=m" (*fx), "m" (*fx));

	/* See comment in fpu_fxsave() below. */
	return check_insn(rex64/fxsave (%[fx]), "=m" (*fx), [fx] "R" (fx));
}

static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
{
	if (config_enabled(CONFIG_X86_32))
		return check_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
	else if (config_enabled(CONFIG_AS_FXSAVEQ))
		return check_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));

	/* See comment in fpu_fxsave() below. */
	return check_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
			  "m" (*fx));
}

static inline int frstor_checking(struct i387_fsave_struct *fx)
{
	return check_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
}

static inline void fpu_fxsave(struct fpu *fpu)
{
	if (config_enabled(CONFIG_X86_32))
		asm volatile( "fxsave %[fx]" : [fx] "=m" (fpu->state->fxsave));
	else if (config_enabled(CONFIG_AS_FXSAVEQ))
		asm volatile("fxsaveq %0" : "=m" (fpu->state->fxsave));
	else {
		/* Using "rex64; fxsave %0" is broken because, if the memory
		 * operand uses any extended registers for addressing, a second
		 * REX prefix will be generated (to the assembler, rex64
		 * followed by semicolon is a separate instruction), and hence
		 * the 64-bitness is lost.
		 *
		 * Using "fxsaveq %0" would be the ideal choice, but is only
		 * supported starting with gas 2.16.
		 *
		 * Using, as a workaround, the properly prefixed form below
		 * isn't accepted by any binutils version so far released,
		 * complaining that the same type of prefix is used twice if
		 * an extended register is needed for addressing (fix submitted
		 * to mainline 2005-11-21).
		 *
		 *  asm volatile("rex64/fxsave %0" : "=m" (fpu->state->fxsave));
		 *
		 * This, however, we can work around by forcing the compiler to
		 * select an addressing mode that doesn't require extended
		 * registers.
		 */
		asm volatile( "rex64/fxsave (%[fx])"
			     : "=m" (fpu->state->fxsave)
			     : [fx] "R" (&fpu->state->fxsave));
	}
}
#ifdef CONFIG_X86_64

int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
			compat_sigset_t *set, struct pt_regs *regs);
int ia32_setup_frame(int sig, struct k_sigaction *ka,
		     compat_sigset_t *set, struct pt_regs *regs);

#else  /* CONFIG_X86_32 */

#define ia32_setup_frame	__setup_frame
#define ia32_setup_rt_frame	__setup_rt_frame

#endif	/* CONFIG_X86_64 */

/*
 * These must be called with preempt disabled. Returns
 * 'true' if the FPU state is still intact.
 */
static inline int fpu_save_init(struct fpu *fpu)
{
	if (use_xsave()) {
		fpu_xsave(fpu);

		/*
		 * xsave header may indicate the init state of the FP.
		 */
		if (!(fpu->state->xsave.xsave_hdr.xstate_bv & XSTATE_FP))
			return 1;
	} else if (use_fxsr()) {
		fpu_fxsave(fpu);
	} else {
		asm volatile("fnsave %[fx]; fwait"
			     : [fx] "=m" (fpu->state->fsave));
		return 0;
	}

	/*
	 * If exceptions are pending, we need to clear them so
	 * that we don't randomly get exceptions later.
	 *
	 * FIXME! Is this perhaps only true for the old-style
	 * irq13 case? Maybe we could leave the x87 state
	 * intact otherwise?
	 */
	if (unlikely(fpu->state->fxsave.swd & X87_FSW_ES)) {
		asm volatile("fnclex");
		return 0;
	}
	return 1;
}

static inline int __save_init_fpu(struct task_struct *tsk)
{
	return fpu_save_init(&tsk->thread.fpu);
}

static inline int fpu_restore_checking(struct fpu *fpu)
{
	if (use_xsave())
		return fpu_xrstor_checking(&fpu->state->xsave);
	else if (use_fxsr())
		return fxrstor_checking(&fpu->state->fxsave);
	else
		return frstor_checking(&fpu->state->fsave);
}

static inline int restore_fpu_checking(struct task_struct *tsk)
{
	/* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception
	   is pending.  Clear the x87 state here by setting it to fixed
	   values. "m" is a random variable that should be in L1 */
	alternative_input(
		ASM_NOP8 ASM_NOP2,
		"emms\n\t"		/* clear stack tags */
		"fildl %P[addr]",	/* set F?P to defined value */
		X86_FEATURE_FXSAVE_LEAK,
		[addr] "m" (tsk->thread.fpu.has_fpu));

	return fpu_restore_checking(&tsk->thread.fpu);
}

/*
 * Software FPU state helpers. Careful: these need to
 * be preemption protection *and* they need to be
 * properly paired with the CR0.TS changes!
 */
static inline int __thread_has_fpu(struct task_struct *tsk)
{
	return tsk->thread.fpu.has_fpu;
}

/* Must be paired with an 'stts' after! */
static inline void __thread_clear_has_fpu(struct task_struct *tsk)
{
	tsk->thread.fpu.has_fpu = 0;
	this_cpu_write(fpu_owner_task, NULL);
}

/* Must be paired with a 'clts' before! */
static inline void __thread_set_has_fpu(struct task_struct *tsk)
{
	tsk->thread.fpu.has_fpu = 1;
	this_cpu_write(fpu_owner_task, tsk);
}

/*
 * Encapsulate the CR0.TS handling together with the
 * software flag.
 *
 * These generally need preemption protection to work,
 * do try to avoid using these on their own.
 */
static inline void __thread_fpu_end(struct task_struct *tsk)
{
	__thread_clear_has_fpu(tsk);
	stts();
}

static inline void __thread_fpu_begin(struct task_struct *tsk)
{
	clts();
	__thread_set_has_fpu(tsk);
}

/*
 * FPU state switching for scheduling.
 *
 * This is a two-stage process:
 *
 *  - switch_fpu_prepare() saves the old state and
 *    sets the new state of the CR0.TS bit. This is
 *    done within the context of the old process.
 *
 *  - switch_fpu_finish() restores the new state as
 *    necessary.
 */
typedef struct { int preload; } fpu_switch_t;

/*
 * FIXME! We could do a totally lazy restore, but we need to
 * add a per-cpu "this was the task that last touched the FPU
 * on this CPU" variable, and the task needs to have a "I last
 * touched the FPU on this CPU" and check them.
 *
 * We don't do that yet, so "fpu_lazy_restore()" always returns
 * false, but some day..
 */
static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)
{
	return new == this_cpu_read_stable(fpu_owner_task) &&
		cpu == new->thread.fpu.last_cpu;
}

static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct task_struct *new, int cpu)
{
	fpu_switch_t fpu;

	fpu.preload = tsk_used_math(new) && new->fpu_counter > 5;
	if (__thread_has_fpu(old)) {
		if (!__save_init_fpu(old))
			cpu = ~0;
		old->thread.fpu.last_cpu = cpu;
		old->thread.fpu.has_fpu = 0;	/* But leave fpu_owner_task! */

		/* Don't change CR0.TS if we just switch! */
		if (fpu.preload) {
			new->fpu_counter++;
			__thread_set_has_fpu(new);
			prefetch(new->thread.fpu.state);
		} else
			stts();
	} else {
		old->fpu_counter = 0;
		old->thread.fpu.last_cpu = ~0;
		if (fpu.preload) {
			new->fpu_counter++;
			if (fpu_lazy_restore(new, cpu))
				fpu.preload = 0;
			else
				prefetch(new->thread.fpu.state);
			__thread_fpu_begin(new);
		}
	}
	return fpu;
}

/*
 * By the time this gets called, we've already cleared CR0.TS and
 * given the process the FPU if we are going to preload the FPU
 * state - all we need to do is to conditionally restore the register
 * state itself.
 */
static inline void switch_fpu_finish(struct task_struct *new, fpu_switch_t fpu)
{
	if (fpu.preload) {
		if (unlikely(restore_fpu_checking(new)))
			__thread_fpu_end(new);
	}
}

/*
 * Signal frame handlers...
 */
extern int save_i387_xstate(void __user *buf);
extern int restore_i387_xstate(void __user *buf);

static inline void __clear_fpu(struct task_struct *tsk)
{
	if (__thread_has_fpu(tsk)) {
		/* Ignore delayed exceptions from user space */
		asm volatile("1: fwait\n"
			     "2:\n"
			     _ASM_EXTABLE(1b, 2b));
		__thread_fpu_end(tsk);
	}
}

/*
 * The actual user_fpu_begin/end() functions
 * need to be preemption-safe.
 *
 * NOTE! user_fpu_end() must be used only after you
 * have saved the FP state, and user_fpu_begin() must
 * be used only immediately before restoring it.
 * These functions do not do any save/restore on
 * their own.
 */
static inline void user_fpu_end(void)
{
	preempt_disable();
	__thread_fpu_end(current);
	preempt_enable();
}

static inline void user_fpu_begin(void)
{
	preempt_disable();
	if (!user_has_fpu())
		__thread_fpu_begin(current);
	preempt_enable();
}

/*
 * These disable preemption on their own and are safe
 */
static inline void save_init_fpu(struct task_struct *tsk)
{
	WARN_ON_ONCE(!__thread_has_fpu(tsk));
	preempt_disable();
	__save_init_fpu(tsk);
	__thread_fpu_end(tsk);
	preempt_enable();
}

static inline void clear_fpu(struct task_struct *tsk)
{
	preempt_disable();
	__clear_fpu(tsk);
	preempt_enable();
}

/*
 * i387 state interaction
 */
static inline unsigned short get_fpu_cwd(struct task_struct *tsk)
{
	if (cpu_has_fxsr) {
		return tsk->thread.fpu.state->fxsave.cwd;
	} else {
		return (unsigned short)tsk->thread.fpu.state->fsave.cwd;
	}
}

static inline unsigned short get_fpu_swd(struct task_struct *tsk)
{
	if (cpu_has_fxsr) {
		return tsk->thread.fpu.state->fxsave.swd;
	} else {
		return (unsigned short)tsk->thread.fpu.state->fsave.swd;
	}
}

static inline unsigned short get_fpu_mxcsr(struct task_struct *tsk)
{
	if (cpu_has_xmm) {
		return tsk->thread.fpu.state->fxsave.mxcsr;
	} else {
		return MXCSR_DEFAULT;
	}
}

static bool fpu_allocated(struct fpu *fpu)
{
	return fpu->state != NULL;
}

static inline int fpu_alloc(struct fpu *fpu)
{
	if (fpu_allocated(fpu))
		return 0;
	fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
	if (!fpu->state)
		return -ENOMEM;
	WARN_ON((unsigned long)fpu->state & 15);
	return 0;
}

static inline void fpu_free(struct fpu *fpu)
{
	if (fpu->state) {
		kmem_cache_free(task_xstate_cachep, fpu->state);
		fpu->state = NULL;
	}
}

static inline void fpu_copy(struct fpu *dst, struct fpu *src)
{
	memcpy(dst->state, src->state, xstate_size);
}

extern void fpu_finit(struct fpu *fpu);

#endif