fpu.c

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#include <linux/sched.h>
#include <linux/slab.h>
#include <asm/processor.h>
#include <asm/fpu.h>
#include <asm/traps.h>

int init_fpu(struct task_struct *tsk)
{
    if (tsk_used_math(tsk)) {
        if ((boot_cpu_data.flags & CPU_HAS_FPU) && tsk == current)
            unlazy_fpu(tsk, task_pt_regs(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;
    }

    if (boot_cpu_data.flags & CPU_HAS_FPU) {
        struct sh_fpu_hard_struct *fp = &tsk->thread.xstate->hardfpu;
        memset(fp, 0, xstate_size);
        fp->fpscr = FPSCR_INIT;
    } else {
        struct sh_fpu_soft_struct *fp = &tsk->thread.xstate->softfpu;
        memset(fp, 0, xstate_size);
        fp->fpscr = FPSCR_INIT;
    }

    set_stopped_child_used_math(tsk);
    return 0;
}

#ifdef CONFIG_SH_FPU
void __fpu_state_restore(void)
{
    struct task_struct *tsk = current;

    restore_fpu(tsk);

    task_thread_info(tsk)->status |= TS_USEDFPU;
    tsk->fpu_counter++;
}

void fpu_state_restore(struct pt_regs *regs)
{
    struct task_struct *tsk = current;

    if (unlikely(!user_mode(regs))) {
        printk(KERN_ERR "BUG: FPU is used in kernel mode.\n");
        BUG();
        return;
    }

    if (!tsk_used_math(tsk)) {
        local_irq_enable();
        /*
         * does a slab alloc which can sleep
         */
        if (init_fpu(tsk)) {
            /*
             * ran out of memory!
             */
            do_group_exit(SIGKILL);
            return;
        }
        local_irq_disable();
    }

    grab_fpu(regs);

    __fpu_state_restore();
}

BUILD_TRAP_HANDLER(fpu_state_restore)
{
    TRAP_HANDLER_DECL;

    fpu_state_restore(regs);
}
#endif /* CONFIG_SH_FPU */