fpu-internal.h

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/*
 * Copyright (C) 1994 Linus Torvalds
 *
 * Pentium III FXSR, SSE support
 * General FPU state handling cleanups
 *  Gareth Hughes <[email protected]>, 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>
#include <asm/smap.h>

#ifdef CONFIG_X86_64
# include <asm/sigcontext32.h>
# include <asm/user32.h>
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
# define user_i387_ia32_struct  user_i387_struct
# define user32_fxsr_struct user_fxsr_struct
# define ia32_setup_frame   __setup_frame
# define ia32_setup_rt_frame    __setup_rt_frame
#endif

extern unsigned int mxcsr_feature_mask;
extern void fpu_init(void);
extern void eager_fpu_init(void);

DECLARE_PER_CPU(struct task_struct *, fpu_owner_task);

extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
                  struct task_struct *tsk);
extern void convert_to_fxsr(struct task_struct *tsk,
                const struct user_i387_ia32_struct *env);

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

#ifdef CONFIG_MATH_EMULATION
# define HAVE_HWFP      (boot_cpu_data.hard_math)
extern void finit_soft_fpu(struct i387_soft_struct *soft);
#else
# define HAVE_HWFP      1
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_eager_fpu(void)
{
    return static_cpu_has(X86_FEATURE_EAGER_FPU);
}

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);
}

static inline void fx_finit(struct i387_fxsave_struct *fx)
{
    memset(fx, 0, xstate_size);
    fx->cwd = 0x37f;
    fx->mxcsr = MXCSR_DEFAULT;
}

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 user_insn(insn, output, input...)               \
({                                  \
    int err;                            \
    asm volatile(ASM_STAC "\n"                  \
             "1:" #insn "\n\t"                  \
             "2: " ASM_CLAC "\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;                                \
})

#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 user_insn(fnsave %[fx]; fwait,  [fx] "=m" (*fx), "m" (*fx));
}

static inline int fxsave_user(struct i387_fxsave_struct __user *fx)
{
    if (config_enabled(CONFIG_X86_32))
        return user_insn(fxsave %[fx], [fx] "=m" (*fx), "m" (*fx));
    else if (config_enabled(CONFIG_AS_FXSAVEQ))
        return user_insn(fxsaveq %[fx], [fx] "=m" (*fx), "m" (*fx));

    /* See comment in fpu_fxsave() below. */
    return user_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 fxrstor_user(struct i387_fxsave_struct __user *fx)
{
    if (config_enabled(CONFIG_X86_32))
        return user_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
    else if (config_enabled(CONFIG_AS_FXSAVEQ))
        return user_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));

    /* See comment in fpu_fxsave() below. */
    return user_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 int frstor_user(struct i387_fsave_struct __user *fx)
{
    return user_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));
    }
}

/*
 * 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);
    if (!use_eager_fpu())
        stts();
}

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

static inline void __drop_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);
    }
}

static inline void drop_fpu(struct task_struct *tsk)
{
    /*
     * Forget coprocessor state..
     */
    preempt_disable();
    tsk->fpu_counter = 0;
    __drop_fpu(tsk);
    clear_used_math();
    preempt_enable();
}

static inline void drop_init_fpu(struct task_struct *tsk)
{
    if (!use_eager_fpu())
        drop_fpu(tsk);
    else {
        if (use_xsave())
            xrstor_state(init_xstate_buf, -1);
        else
            fxrstor_checking(&init_xstate_buf->i387);
    }
}

/*
 * 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;

/*
 * Must be run with preemption disabled: this clears the fpu_owner_task,
 * on this CPU.
 *
 * This will disable any lazy FPU state restore of the current FPU state,
 * but if the current thread owns the FPU, it will still be saved by.
 */
static inline void __cpu_disable_lazy_restore(unsigned int cpu)
{
    per_cpu(fpu_owner_task, cpu) = NULL;
}

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;

    /*
     * If the task has used the math, pre-load the FPU on xsave processors
     * or if the past 5 consecutive context-switches used math.
     */
    fpu.preload = tsk_used_math(new) && (use_eager_fpu() ||
                         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 if (!use_eager_fpu())
            stts();
    } else {
        old->fpu_counter = 0;
        old->thread.fpu.last_cpu = ~0;
        if (fpu.preload) {
            new->fpu_counter++;
            if (!use_eager_fpu() && 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)))
            drop_init_fpu(new);
    }
}

/*
 * Signal frame handlers...
 */
extern int save_xstate_sig(void __user *buf, void __user *fx, int size);
extern int __restore_xstate_sig(void __user *buf, void __user *fx, int size);

static inline int xstate_sigframe_size(void)
{
    return use_xsave() ? xstate_size + FP_XSTATE_MAGIC2_SIZE : xstate_size;
}

static inline int restore_xstate_sig(void __user *buf, int ia32_frame)
{
    void __user *buf_fx = buf;
    int size = xstate_sigframe_size();

    if (ia32_frame && use_fxsr()) {
        buf_fx = buf + sizeof(struct i387_fsave_struct);
        size += sizeof(struct i387_fsave_struct);
    }

    return __restore_xstate_sig(buf, buf_fx, size);
}

/*
 * Need to be preemption-safe.
 *
 * NOTE! user_fpu_begin() must be used only immediately before restoring
 * it. This function does not do any save/restore on their own.
 */
static inline void user_fpu_begin(void)
{
    preempt_disable();
    if (!user_has_fpu())
        __thread_fpu_begin(current);
    preempt_enable();
}

static inline void __save_fpu(struct task_struct *tsk)
{
    if (use_xsave())
        xsave_state(&tsk->thread.fpu.state->xsave, -1);
    else
        fpu_fxsave(&tsk->thread.fpu);
}

/*
 * 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));

    if (use_eager_fpu()) {
        __save_fpu(tsk);
        return;
    }

    preempt_disable();
    __save_init_fpu(tsk);
    __thread_fpu_end(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 task_struct *dst, struct task_struct *src)
{
    if (use_eager_fpu()) {
        memset(&dst->thread.fpu.state->xsave, 0, xstate_size);
        __save_fpu(dst);
    } else {
        struct fpu *dfpu = &dst->thread.fpu;
        struct fpu *sfpu = &src->thread.fpu;

        unlazy_fpu(src);
        memcpy(dfpu->state, sfpu->state, xstate_size);
    }
}

static inline unsigned long
alloc_mathframe(unsigned long sp, int ia32_frame, unsigned long *buf_fx,
        unsigned long *size)
{
    unsigned long frame_size = xstate_sigframe_size();

    *buf_fx = sp = round_down(sp - frame_size, 64);
    if (ia32_frame && use_fxsr()) {
        frame_size += sizeof(struct i387_fsave_struct);
        sp -= sizeof(struct i387_fsave_struct);
    }

    *size = frame_size;
    return sp;
}

#endif