自学教程：C++ vfp_sync_hwstate函数代码示例

static void vfp_thread_copy(struct thread_info *thread){	struct thread_info *parent = current_thread_info();	vfp_sync_hwstate(parent);	thread->vfpstate = parent->vfpstate;}

/* * VFP register get/set implementations. * * With respect to the kernel, struct user_fp is divided into three chunks: * 16 or 32 real VFP registers (d0-d15 or d0-31) *	These are transferred to/from the real registers in the task's *	vfp_hard_struct.  The number of registers depends on the kernel *	configuration. * * 16 or 0 fake VFP registers (d16-d31 or empty) *	i.e., the user_vfp structure has space for 32 registers even if *	the kernel doesn't have them all. * *	vfp_get() reads this chunk as zero where applicable *	vfp_set() ignores this chunk * * 1 word for the FPSCR * * The bounds-checking logic built into user_regset_copyout and friends * means that we can make a simple sequence of calls to map the relevant data * to/from the specified slice of the user regset structure. */static int vfp_get(struct task_struct *target,		   const struct user_regset *regset,		   unsigned int pos, unsigned int count,		   void *kbuf, void __user *ubuf){	int ret;	struct thread_info *thread = task_thread_info(target);	struct vfp_hard_struct const *vfp = &thread->vfpstate.hard;	const size_t user_fpregs_offset = offsetof(struct user_vfp, fpregs);	const size_t user_fpscr_offset = offsetof(struct user_vfp, fpscr);	vfp_sync_hwstate(thread);	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,				  &vfp->fpregs,				  user_fpregs_offset,				  user_fpregs_offset + sizeof(vfp->fpregs));	if (ret)		return ret;	ret = user_regset_copyout_zero(&pos, &count, &kbuf, &ubuf,				       user_fpregs_offset + sizeof(vfp->fpregs),				       user_fpscr_offset);	if (ret)		return ret;	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,				   &vfp->fpscr,				   user_fpscr_offset,				   user_fpscr_offset + sizeof(vfp->fpscr));}

int vfp_preserve_user_clear_hwstate(struct user_vfp __user *ufp,				    struct user_vfp_exc __user *ufp_exc){	struct thread_info *thread = current_thread_info();	struct vfp_hard_struct *hwstate = &thread->vfpstate.hard;	int err = 0;		vfp_sync_hwstate(thread);	err |= __copy_to_user(&ufp->fpregs, &hwstate->fpregs,			      sizeof(hwstate->fpregs));	__put_user_error(hwstate->fpscr, &ufp->fpscr, err);	__put_user_error(hwstate->fpexc, &ufp_exc->fpexc, err);	__put_user_error(hwstate->fpinst, &ufp_exc->fpinst, err);	__put_user_error(hwstate->fpinst2, &ufp_exc->fpinst2, err);	if (err)		return -EFAULT;		vfp_flush_hwstate(thread);	hwstate->fpscr &= ~(FPSCR_LENGTH_MASK | FPSCR_STRIDE_MASK);	return 0;}

static int preserve_vfp_context(struct vfp_sigframe __user *frame){	struct thread_info *thread = current_thread_info();	struct vfp_hard_struct *h = &thread->vfpstate.hard;	const unsigned long magic = VFP_MAGIC;	const unsigned long size = VFP_STORAGE_SIZE;	int err = 0;	vfp_sync_hwstate(thread);	__put_user_error(magic, &frame->magic, err);	__put_user_error(size, &frame->size, err);	/*	 * Copy the floating point registers. There can be unused	 * registers see asm/hwcap.h for details.	 */	err |= __copy_to_user(&frame->ufp.fpregs, &h->fpregs,			      sizeof(h->fpregs));	/*	 * Copy the status and control register.	 */	__put_user_error(h->fpscr, &frame->ufp.fpscr, err);	/*	 * Copy the exception registers.	 */	__put_user_error(h->fpexc, &frame->ufp_exc.fpexc, err);	__put_user_error(h->fpinst, &frame->ufp_exc.fpinst, err);	__put_user_error(h->fpinst2, &frame->ufp_exc.fpinst2, err);	return err ? -EFAULT : 0;}

static void vfp_thread_copy(struct thread_info *thread){	struct thread_info *parent = current_thread_info();	vfp_sync_hwstate(parent);	thread->vfpstate = parent->vfpstate;#ifdef CONFIG_SMP	thread->vfpstate.hard.cpu = NR_CPUS;#endif}