x86/fpu: Don't reset thread.fpu_counter

[linux/fpc-iii.git] / arch / x86 / kernel / i387.c

/*
 *  Copyright (C) 1994 Linus Torvalds
 *
 *  Pentium III FXSR, SSE support
 *  General FPU state handling cleanups
 *      Gareth Hughes <gareth@valinux.com>, May 2000
 */
#include <linux/module.h>
#include <linux/regset.h>
#include <linux/sched.h>
#include <linux/slab.h>

#include <asm/sigcontext.h>
#include <asm/processor.h>
#include <asm/math_emu.h>
#include <asm/uaccess.h>
#include <asm/ptrace.h>
#include <asm/i387.h>
#include <asm/fpu-internal.h>
#include <asm/user.h>

/*
 * Were we in an interrupt that interrupted kernel mode?
 *
 * On others, we can do a kernel_fpu_begin/end() pair *ONLY* if that
 * pair does nothing at all: the thread must not have fpu (so
 * that we don't try to save the FPU state), and TS must
 * be set (so that the clts/stts pair does nothing that is
 * visible in the interrupted kernel thread).
 *
 * Except for the eagerfpu case when we return 1 unless we've already
 * been eager and saved the state in kernel_fpu_begin().
 */
static inline bool interrupted_kernel_fpu_idle(void)
{
        if (use_eager_fpu())
                return __thread_has_fpu(current);

        return !__thread_has_fpu(current) &&
                (read_cr0() & X86_CR0_TS);
}

/*
 * Were we in user mode (or vm86 mode) when we were
 * interrupted?
 *
 * Doing kernel_fpu_begin/end() is ok if we are running
 * in an interrupt context from user mode - we'll just
 * save the FPU state as required.
 */
static inline bool interrupted_user_mode(void)
{
        struct pt_regs *regs = get_irq_regs();
        return regs && user_mode_vm(regs);
}

/*
 * Can we use the FPU in kernel mode with the
 * whole "kernel_fpu_begin/end()" sequence?
 *
 * It's always ok in process context (ie "not interrupt")
 * but it is sometimes ok even from an irq.
 */
bool irq_fpu_usable(void)
{
        return !in_interrupt() ||
                interrupted_user_mode() ||
                interrupted_kernel_fpu_idle();
}
EXPORT_SYMBOL(irq_fpu_usable);

void __kernel_fpu_begin(void)
{
        struct task_struct *me = current;

        if (__thread_has_fpu(me)) {
                __thread_clear_has_fpu(me);
                __save_init_fpu(me);
                /* We do 'stts()' in __kernel_fpu_end() */
        } else if (!use_eager_fpu()) {
                this_cpu_write(fpu_owner_task, NULL);
                clts();
        }
}
EXPORT_SYMBOL(__kernel_fpu_begin);

void __kernel_fpu_end(void)
{
        if (use_eager_fpu()) {
                /*
                 * For eager fpu, most the time, tsk_used_math() is true.
                 * Restore the user math as we are done with the kernel usage.
                 * At few instances during thread exit, signal handling etc,
                 * tsk_used_math() is false. Those few places will take proper
                 * actions, so we don't need to restore the math here.
                 */
                if (likely(tsk_used_math(current)))
                        math_state_restore();
        } else {
                stts();
        }
}
EXPORT_SYMBOL(__kernel_fpu_end);

void unlazy_fpu(struct task_struct *tsk)
{
        preempt_disable();
        if (__thread_has_fpu(tsk)) {
                __save_init_fpu(tsk);
                __thread_fpu_end(tsk);
        }
        preempt_enable();
}
EXPORT_SYMBOL(unlazy_fpu);

unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
unsigned int xstate_size;
EXPORT_SYMBOL_GPL(xstate_size);
static struct i387_fxsave_struct fx_scratch;

static void mxcsr_feature_mask_init(void)
{
        unsigned long mask = 0;

        if (cpu_has_fxsr) {
                memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
                asm volatile("fxsave %0" : "+m" (fx_scratch));
                mask = fx_scratch.mxcsr_mask;
                if (mask == 0)
                        mask = 0x0000ffbf;
        }
        mxcsr_feature_mask &= mask;
}

static void init_thread_xstate(void)
{
        /*
         * Note that xstate_size might be overwriten later during
         * xsave_init().
         */

        if (!cpu_has_fpu) {
                /*
                 * Disable xsave as we do not support it if i387
                 * emulation is enabled.
                 */
                setup_clear_cpu_cap(X86_FEATURE_XSAVE);
                setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
                xstate_size = sizeof(struct i387_soft_struct);
                return;
        }

        if (cpu_has_fxsr)
                xstate_size = sizeof(struct i387_fxsave_struct);
        else
                xstate_size = sizeof(struct i387_fsave_struct);
}

/*
 * Called at bootup to set up the initial FPU state that is later cloned
 * into all processes.
 */

void fpu_init(void)
{
        unsigned long cr0;
        unsigned long cr4_mask = 0;

#ifndef CONFIG_MATH_EMULATION
        if (!cpu_has_fpu) {
                pr_emerg("No FPU found and no math emulation present\n");
                pr_emerg("Giving up\n");
                for (;;)
                        asm volatile("hlt");
        }
#endif
        if (cpu_has_fxsr)
                cr4_mask |= X86_CR4_OSFXSR;
        if (cpu_has_xmm)
                cr4_mask |= X86_CR4_OSXMMEXCPT;
        if (cr4_mask)
                set_in_cr4(cr4_mask);

        cr0 = read_cr0();
        cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */
        if (!cpu_has_fpu)
                cr0 |= X86_CR0_EM;
        write_cr0(cr0);

        /*
         * init_thread_xstate is only called once to avoid overriding
         * xstate_size during boot time or during CPU hotplug.
         */
        if (xstate_size == 0)
                init_thread_xstate();

        mxcsr_feature_mask_init();
        xsave_init();
        eager_fpu_init();
}

void fpu_finit(struct fpu *fpu)
{
        if (!cpu_has_fpu) {
                finit_soft_fpu(&fpu->state->soft);
                return;
        }

        if (cpu_has_fxsr) {
                fx_finit(&fpu->state->fxsave);
        } else {
                struct i387_fsave_struct *fp = &fpu->state->fsave;
                memset(fp, 0, xstate_size);
                fp->cwd = 0xffff037fu;
                fp->swd = 0xffff0000u;
                fp->twd = 0xffffffffu;
                fp->fos = 0xffff0000u;
        }
}
EXPORT_SYMBOL_GPL(fpu_finit);

/*
 * The _current_ task is using the FPU for the first time
 * so initialize it and set the mxcsr to its default
 * value at reset if we support XMM instructions and then
 * remember the current task has used the FPU.
 */
int init_fpu(struct task_struct *tsk)
{
        int ret;

        if (tsk_used_math(tsk)) {
                if (cpu_has_fpu && tsk == current)
                        unlazy_fpu(tsk);
                tsk->thread.fpu.last_cpu = ~0;
                return 0;
        }

        /*
         * Memory allocation at the first usage of the FPU and other state.
         */
        ret = fpu_alloc(&tsk->thread.fpu);
        if (ret)
                return ret;

        fpu_finit(&tsk->thread.fpu);

        set_stopped_child_used_math(tsk);
        return 0;
}
EXPORT_SYMBOL_GPL(init_fpu);

/*
 * The xstateregs_active() routine is the same as the fpregs_active() routine,
 * as the "regset->n" for the xstate regset will be updated based on the feature
 * capabilites supported by the xsave.
 */
int fpregs_active(struct task_struct *target, const struct user_regset *regset)
{
        return tsk_used_math(target) ? regset->n : 0;
}

int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
{
        return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
}

int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
                unsigned int pos, unsigned int count,
                void *kbuf, void __user *ubuf)
{
        int ret;

        if (!cpu_has_fxsr)
                return -ENODEV;

        ret = init_fpu(target);
        if (ret)
                return ret;

        sanitize_i387_state(target);

        return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
                                   &target->thread.fpu.state->fxsave, 0, -1);
}

int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
                unsigned int pos, unsigned int count,
                const void *kbuf, const void __user *ubuf)
{
        int ret;

        if (!cpu_has_fxsr)
                return -ENODEV;

        ret = init_fpu(target);
        if (ret)
                return ret;

        sanitize_i387_state(target);

        ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
                                 &target->thread.fpu.state->fxsave, 0, -1);

        /*
         * mxcsr reserved bits must be masked to zero for security reasons.
         */
        target->thread.fpu.state->fxsave.mxcsr &= mxcsr_feature_mask;

        /*
         * update the header bits in the xsave header, indicating the
         * presence of FP and SSE state.
         */
        if (cpu_has_xsave)
                target->thread.fpu.state->xsave.xsave_hdr.xstate_bv |= XSTATE_FPSSE;

        return ret;
}

int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
                unsigned int pos, unsigned int count,
                void *kbuf, void __user *ubuf)
{
        int ret;

        if (!cpu_has_xsave)
                return -ENODEV;

        ret = init_fpu(target);
        if (ret)
                return ret;

        /*
         * Copy the 48bytes defined by the software first into the xstate
         * memory layout in the thread struct, so that we can copy the entire
         * xstateregs to the user using one user_regset_copyout().
         */
        memcpy(&target->thread.fpu.state->fxsave.sw_reserved,
               xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));

        /*
         * Copy the xstate memory layout.
         */
        ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
                                  &target->thread.fpu.state->xsave, 0, -1);
        return ret;
}

int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
                  unsigned int pos, unsigned int count,
                  const void *kbuf, const void __user *ubuf)
{
        int ret;
        struct xsave_hdr_struct *xsave_hdr;

        if (!cpu_has_xsave)
                return -ENODEV;

        ret = init_fpu(target);
        if (ret)
                return ret;

        ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
                                 &target->thread.fpu.state->xsave, 0, -1);

        /*
         * mxcsr reserved bits must be masked to zero for security reasons.
         */
        target->thread.fpu.state->fxsave.mxcsr &= mxcsr_feature_mask;

        xsave_hdr = &target->thread.fpu.state->xsave.xsave_hdr;

        xsave_hdr->xstate_bv &= pcntxt_mask;
        /*
         * These bits must be zero.
         */
        memset(xsave_hdr->reserved, 0, 48);

        return ret;
}

#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION

/*
 * FPU tag word conversions.
 */

static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
{
        unsigned int tmp; /* to avoid 16 bit prefixes in the code */

        /* Transform each pair of bits into 01 (valid) or 00 (empty) */
        tmp = ~twd;
        tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
        /* and move the valid bits to the lower byte. */
        tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
        tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
        tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */

        return tmp;
}

#define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16)
#define FP_EXP_TAG_VALID        0
#define FP_EXP_TAG_ZERO         1
#define FP_EXP_TAG_SPECIAL      2
#define FP_EXP_TAG_EMPTY        3

static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
{
        struct _fpxreg *st;
        u32 tos = (fxsave->swd >> 11) & 7;
        u32 twd = (unsigned long) fxsave->twd;
        u32 tag;
        u32 ret = 0xffff0000u;
        int i;

        for (i = 0; i < 8; i++, twd >>= 1) {
                if (twd & 0x1) {
                        st = FPREG_ADDR(fxsave, (i - tos) & 7);

                        switch (st->exponent & 0x7fff) {
                        case 0x7fff:
                                tag = FP_EXP_TAG_SPECIAL;
                                break;
                        case 0x0000:
                                if (!st->significand[0] &&
                                    !st->significand[1] &&
                                    !st->significand[2] &&
                                    !st->significand[3])
                                        tag = FP_EXP_TAG_ZERO;
                                else
                                        tag = FP_EXP_TAG_SPECIAL;
                                break;
                        default:
                                if (st->significand[3] & 0x8000)
                                        tag = FP_EXP_TAG_VALID;
                                else
                                        tag = FP_EXP_TAG_SPECIAL;
                                break;
                        }
                } else {
                        tag = FP_EXP_TAG_EMPTY;
                }
                ret |= tag << (2 * i);
        }
        return ret;
}

/*
 * FXSR floating point environment conversions.
 */

void
convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
{
        struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state->fxsave;
        struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
        struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
        int i;

        env->cwd = fxsave->cwd | 0xffff0000u;
        env->swd = fxsave->swd | 0xffff0000u;
        env->twd = twd_fxsr_to_i387(fxsave);

#ifdef CONFIG_X86_64
        env->fip = fxsave->rip;
        env->foo = fxsave->rdp;
        /*
         * should be actually ds/cs at fpu exception time, but
         * that information is not available in 64bit mode.
         */
        env->fcs = task_pt_regs(tsk)->cs;
        if (tsk == current) {
                savesegment(ds, env->fos);
        } else {
                env->fos = tsk->thread.ds;
        }
        env->fos |= 0xffff0000;
#else
        env->fip = fxsave->fip;
        env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
        env->foo = fxsave->foo;
        env->fos = fxsave->fos;
#endif

        for (i = 0; i < 8; ++i)
                memcpy(&to[i], &from[i], sizeof(to[0]));
}

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

{
        struct i387_fxsave_struct *fxsave = &tsk->thread.fpu.state->fxsave;
        struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
        struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
        int i;

        fxsave->cwd = env->cwd;
        fxsave->swd = env->swd;
        fxsave->twd = twd_i387_to_fxsr(env->twd);
        fxsave->fop = (u16) ((u32) env->fcs >> 16);
#ifdef CONFIG_X86_64
        fxsave->rip = env->fip;
        fxsave->rdp = env->foo;
        /* cs and ds ignored */
#else
        fxsave->fip = env->fip;
        fxsave->fcs = (env->fcs & 0xffff);
        fxsave->foo = env->foo;
        fxsave->fos = env->fos;
#endif

        for (i = 0; i < 8; ++i)
                memcpy(&to[i], &from[i], sizeof(from[0]));
}

int fpregs_get(struct task_struct *target, const struct user_regset *regset,
               unsigned int pos, unsigned int count,
               void *kbuf, void __user *ubuf)
{
        struct user_i387_ia32_struct env;
        int ret;

        ret = init_fpu(target);
        if (ret)
                return ret;

        if (!static_cpu_has(X86_FEATURE_FPU))
                return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);

        if (!cpu_has_fxsr)
                return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
                                           &target->thread.fpu.state->fsave, 0,
                                           -1);

        sanitize_i387_state(target);

        if (kbuf && pos == 0 && count == sizeof(env)) {
                convert_from_fxsr(kbuf, target);
                return 0;
        }

        convert_from_fxsr(&env, target);

        return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
}

int fpregs_set(struct task_struct *target, const struct user_regset *regset,
               unsigned int pos, unsigned int count,
               const void *kbuf, const void __user *ubuf)
{
        struct user_i387_ia32_struct env;
        int ret;

        ret = init_fpu(target);
        if (ret)
                return ret;

        sanitize_i387_state(target);

        if (!static_cpu_has(X86_FEATURE_FPU))
                return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);

        if (!cpu_has_fxsr)
                return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
                                          &target->thread.fpu.state->fsave, 0,
                                          -1);

        if (pos > 0 || count < sizeof(env))
                convert_from_fxsr(&env, target);

        ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
        if (!ret)
                convert_to_fxsr(target, &env);

        /*
         * update the header bit in the xsave header, indicating the
         * presence of FP.
         */
        if (cpu_has_xsave)
                target->thread.fpu.state->xsave.xsave_hdr.xstate_bv |= XSTATE_FP;
        return ret;
}

/*
 * FPU state for core dumps.
 * This is only used for a.out dumps now.
 * It is declared generically using elf_fpregset_t (which is
 * struct user_i387_struct) but is in fact only used for 32-bit
 * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
 */
int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
{
        struct task_struct *tsk = current;
        int fpvalid;

        fpvalid = !!used_math();
        if (fpvalid)
                fpvalid = !fpregs_get(tsk, NULL,
                                      0, sizeof(struct user_i387_ia32_struct),
                                      fpu, NULL);

        return fpvalid;
}
EXPORT_SYMBOL(dump_fpu);

#endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */

static int __init no_387(char *s)
{
        setup_clear_cpu_cap(X86_FEATURE_FPU);
        return 1;
}

__setup("no387", no_387);

void fpu_detect(struct cpuinfo_x86 *c)
{
        unsigned long cr0;
        u16 fsw, fcw;

        fsw = fcw = 0xffff;

        cr0 = read_cr0();
        cr0 &= ~(X86_CR0_TS | X86_CR0_EM);
        write_cr0(cr0);

        asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
                     : "+m" (fsw), "+m" (fcw));

        if (fsw == 0 && (fcw & 0x103f) == 0x003f)
                set_cpu_cap(c, X86_FEATURE_FPU);
        else
                clear_cpu_cap(c, X86_FEATURE_FPU);

        /* The final cr0 value is set in fpu_init() */
}