airport: remove useless return in a function returning void

[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 <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/user.h>

#ifdef CONFIG_X86_64
# include <asm/sigcontext32.h>
# include <asm/user32.h>
#else
# define save_i387_xstate_ia32          save_i387_xstate
# define restore_i387_xstate_ia32       restore_i387_xstate
# define _fpstate_ia32          _fpstate
# define _xstate_ia32           _xstate
# define sig_xstate_ia32_size   sig_xstate_size
# define fx_sw_reserved_ia32    fx_sw_reserved
# define user_i387_ia32_struct  user_i387_struct
# define user32_fxsr_struct     user_fxsr_struct
#endif

#ifdef CONFIG_MATH_EMULATION
# define HAVE_HWFP              (boot_cpu_data.hard_math)
#else
# define HAVE_HWFP              1
#endif

static unsigned int             mxcsr_feature_mask __read_mostly = 0xffffffffu;
unsigned int xstate_size;
unsigned int sig_xstate_ia32_size = sizeof(struct _fpstate_ia32);
static struct i387_fxsave_struct fx_scratch __cpuinitdata;

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

        clts();
        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;
        stts();
}

void __cpuinit init_thread_xstate(void)
{
        if (!HAVE_HWFP) {
                xstate_size = sizeof(struct i387_soft_struct);
                return;
        }

        if (cpu_has_xsave) {
                xsave_cntxt_init();
                return;
        }

        if (cpu_has_fxsr)
                xstate_size = sizeof(struct i387_fxsave_struct);
#ifdef CONFIG_X86_32
        else
                xstate_size = sizeof(struct i387_fsave_struct);
#endif
}

#ifdef CONFIG_X86_64
/*
 * Called at bootup to set up the initial FPU state that is later cloned
 * into all processes.
 */
void __cpuinit fpu_init(void)
{
        unsigned long oldcr0 = read_cr0();

        set_in_cr4(X86_CR4_OSFXSR);
        set_in_cr4(X86_CR4_OSXMMEXCPT);

        write_cr0(oldcr0 & ~(X86_CR0_TS|X86_CR0_EM)); /* clear TS and EM */

        /*
         * Boot processor to setup the FP and extended state context info.
         */
        if (!smp_processor_id())
                init_thread_xstate();
        xsave_init();

        mxcsr_feature_mask_init();
        /* clean state in init */
        if (cpu_has_xsave)
                current_thread_info()->status = TS_XSAVE;
        else
                current_thread_info()->status = 0;
        clear_used_math();
}
#endif  /* CONFIG_X86_64 */

/*
 * 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
 * remeber the current task has used the FPU.
 */
int init_fpu(struct task_struct *tsk)
{
        if (tsk_used_math(tsk)) {
                if (HAVE_HWFP && tsk == current)
                        unlazy_fpu(tsk);
                return 0;
        }

        /*
         * Memory allocation at the first usage of the FPU and other state.
         */
        if (!tsk->thread.xstate) {
                tsk->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
                                                      GFP_KERNEL);
                if (!tsk->thread.xstate)
                        return -ENOMEM;
        }

#ifdef CONFIG_X86_32
        if (!HAVE_HWFP) {
                memset(tsk->thread.xstate, 0, xstate_size);
                finit();
                set_stopped_child_used_math(tsk);
                return 0;
        }
#endif

        if (cpu_has_fxsr) {
                struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;

                memset(fx, 0, xstate_size);
                fx->cwd = 0x37f;
                if (cpu_has_xmm)
                        fx->mxcsr = MXCSR_DEFAULT;
        } else {
                struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
                memset(fp, 0, xstate_size);
                fp->cwd = 0xffff037fu;
                fp->swd = 0xffff0000u;
                fp->twd = 0xffffffffu;
                fp->fos = 0xffff0000u;
        }
        /*
         * Only the device not available exception or ptrace can call init_fpu.
         */
        set_stopped_child_used_math(tsk);
        return 0;
}

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;

        return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
                                   &target->thread.xstate->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;

        set_stopped_child_used_math(target);

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

        /*
         * mxcsr reserved bits must be masked to zero for security reasons.
         */
        target->thread.xstate->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.xstate->xsave.xsave_hdr.xstate_bv |= XSTATE_FPSSE;

        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.
 */

static void
convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
{
        struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->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;
        if (tsk == current) {
                /*
                 * should be actually ds/cs at fpu exception time, but
                 * that information is not available in 64bit mode.
                 */
                asm("mov %%ds, %[fos]" : [fos] "=r" (env->fos));
                asm("mov %%cs, %[fcs]" : [fcs] "=r" (env->fcs));
        } else {
                struct pt_regs *regs = task_pt_regs(tsk);

                env->fos = 0xffff0000 | tsk->thread.ds;
                env->fcs = regs->cs;
        }
#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]));
}

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

{
        struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->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 (!HAVE_HWFP)
                return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);

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

        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;

        set_stopped_child_used_math(target);

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

        if (!cpu_has_fxsr) {
                return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
                                          &target->thread.xstate->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.xstate->xsave.xsave_hdr.xstate_bv |= XSTATE_FP;
        return ret;
}

/*
 * Signal frame handlers.
 */

static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
{
        struct task_struct *tsk = current;
        struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;

        fp->status = fp->swd;
        if (__copy_to_user(buf, fp, sizeof(struct i387_fsave_struct)))
                return -1;
        return 1;
}

static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
{
        struct task_struct *tsk = current;
        struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
        struct user_i387_ia32_struct env;
        int err = 0;

        convert_from_fxsr(&env, tsk);
        if (__copy_to_user(buf, &env, sizeof(env)))
                return -1;

        err |= __put_user(fx->swd, &buf->status);
        err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
        if (err)
                return -1;

        if (__copy_to_user(&buf->_fxsr_env[0], fx, xstate_size))
                return -1;
        return 1;
}

static int save_i387_xsave(void __user *buf)
{
        struct task_struct *tsk = current;
        struct _fpstate_ia32 __user *fx = buf;
        int err = 0;

        /*
         * For legacy compatible, we always set FP/SSE bits in the bit
         * vector while saving the state to the user context.
         * This will enable us capturing any changes(during sigreturn) to
         * the FP/SSE bits by the legacy applications which don't touch
         * xstate_bv in the xsave header.
         *
         * xsave aware applications can change the xstate_bv in the xsave
         * header as well as change any contents in the memory layout.
         * xrestore as part of sigreturn will capture all the changes.
         */
        tsk->thread.xstate->xsave.xsave_hdr.xstate_bv |= XSTATE_FPSSE;

        if (save_i387_fxsave(fx) < 0)
                return -1;

        err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved_ia32,
                             sizeof(struct _fpx_sw_bytes));
        err |= __put_user(FP_XSTATE_MAGIC2,
                          (__u32 __user *) (buf + sig_xstate_ia32_size
                                            - FP_XSTATE_MAGIC2_SIZE));
        if (err)
                return -1;

        return 1;
}

int save_i387_xstate_ia32(void __user *buf)
{
        struct _fpstate_ia32 __user *fp = (struct _fpstate_ia32 __user *) buf;
        struct task_struct *tsk = current;

        if (!used_math())
                return 0;

        if (!access_ok(VERIFY_WRITE, buf, sig_xstate_ia32_size))
                return -EACCES;
        /*
         * This will cause a "finit" to be triggered by the next
         * attempted FPU operation by the 'current' process.
         */
        clear_used_math();

        if (!HAVE_HWFP) {
                return fpregs_soft_get(current, NULL,
                                       0, sizeof(struct user_i387_ia32_struct),
                                       NULL, fp) ? -1 : 1;
        }

        unlazy_fpu(tsk);

        if (cpu_has_xsave)
                return save_i387_xsave(fp);
        if (cpu_has_fxsr)
                return save_i387_fxsave(fp);
        else
                return save_i387_fsave(fp);
}

static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
{
        struct task_struct *tsk = current;

        return __copy_from_user(&tsk->thread.xstate->fsave, buf,
                                sizeof(struct i387_fsave_struct));
}

static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf,
                               unsigned int size)
{
        struct task_struct *tsk = current;
        struct user_i387_ia32_struct env;
        int err;

        err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
                               size);
        /* mxcsr reserved bits must be masked to zero for security reasons */
        tsk->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
        if (err || __copy_from_user(&env, buf, sizeof(env)))
                return 1;
        convert_to_fxsr(tsk, &env);

        return 0;
}

static int restore_i387_xsave(void __user *buf)
{
        struct _fpx_sw_bytes fx_sw_user;
        struct _fpstate_ia32 __user *fx_user =
                        ((struct _fpstate_ia32 __user *) buf);
        struct i387_fxsave_struct __user *fx =
                (struct i387_fxsave_struct __user *) &fx_user->_fxsr_env[0];
        struct xsave_hdr_struct *xsave_hdr =
                                &current->thread.xstate->xsave.xsave_hdr;
        u64 mask;
        int err;

        if (check_for_xstate(fx, buf, &fx_sw_user))
                goto fx_only;

        mask = fx_sw_user.xstate_bv;

        err = restore_i387_fxsave(buf, fx_sw_user.xstate_size);

        xsave_hdr->xstate_bv &= pcntxt_mask;
        /*
         * These bits must be zero.
         */
        xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;

        /*
         * Init the state that is not present in the memory layout
         * and enabled by the OS.
         */
        mask = ~(pcntxt_mask & ~mask);
        xsave_hdr->xstate_bv &= mask;

        return err;
fx_only:
        /*
         * Couldn't find the extended state information in the memory
         * layout. Restore the FP/SSE and init the other extended state
         * enabled by the OS.
         */
        xsave_hdr->xstate_bv = XSTATE_FPSSE;
        return restore_i387_fxsave(buf, sizeof(struct i387_fxsave_struct));
}

int restore_i387_xstate_ia32(void __user *buf)
{
        int err;
        struct task_struct *tsk = current;
        struct _fpstate_ia32 __user *fp = (struct _fpstate_ia32 __user *) buf;

        if (HAVE_HWFP)
                clear_fpu(tsk);

        if (!buf) {
                if (used_math()) {
                        clear_fpu(tsk);
                        clear_used_math();
                }

                return 0;
        } else
                if (!access_ok(VERIFY_READ, buf, sig_xstate_ia32_size))
                        return -EACCES;

        if (!used_math()) {
                err = init_fpu(tsk);
                if (err)
                        return err;
        }

        if (HAVE_HWFP) {
                if (cpu_has_xsave)
                        err = restore_i387_xsave(buf);
                else if (cpu_has_fxsr)
                        err = restore_i387_fxsave(fp, sizeof(struct
                                                           i387_fxsave_struct));
                else
                        err = restore_i387_fsave(fp);
        } else {
                err = fpregs_soft_set(current, NULL,
                                      0, sizeof(struct user_i387_ia32_struct),
                                      NULL, fp) != 0;
        }
        set_used_math();

        return err;
}

/*
 * 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 */