Function fpu_kern_enter

freebsd/amd64/amd64/fpu.c:1147–1197

}

void
fpu_kern_enter(struct thread *td, struct fpu_kern_ctx *ctx, u_int flags)
{
	struct pcb *pcb;

	pcb = td->td_pcb;
	KASSERT((flags & FPU_KERN_NOCTX) != 0 || ctx != NULL,
	    ("ctx is required when !FPU_KERN_NOCTX"));
	KASSERT(ctx == NULL || (ctx->flags & FPU_KERN_CTX_INUSE) == 0,
	    ("using inuse ctx"));
	KASSERT((pcb->pcb_flags & PCB_FPUNOSAVE) == 0,
	    ("recursive fpu_kern_enter while in PCB_FPUNOSAVE state"));

	if ((flags & FPU_KERN_NOCTX) != 0) {
		critical_enter();
		stop_emulating();
		if (curthread == PCPU_GET(fpcurthread)) {
			fpusave(curpcb->pcb_save);
			PCPU_SET(fpcurthread, NULL);
		} else {
			KASSERT(PCPU_GET(fpcurthread) == NULL,
			    ("invalid fpcurthread"));
		}

		/*
		 * This breaks XSAVEOPT tracker, but
		 * PCB_FPUNOSAVE state is supposed to never need to
		 * save FPU context at all.
		 */
		fpurestore(fpu_initialstate);
		set_pcb_flags(pcb, PCB_KERNFPU | PCB_FPUNOSAVE |
		    PCB_FPUINITDONE);
		return;
	}
	if ((flags & FPU_KERN_KTHR) != 0 && is_fpu_kern_thread(0)) {
		ctx->flags = FPU_KERN_CTX_DUMMY | FPU_KERN_CTX_INUSE;
		return;
	}
	critical_enter();
	KASSERT(!PCB_USER_FPU(pcb) || pcb->pcb_save ==
	    get_pcb_user_save_pcb(pcb), ("mangled pcb_save"));
	ctx->flags = FPU_KERN_CTX_INUSE;
	if ((pcb->pcb_flags & PCB_FPUINITDONE) != 0)
		ctx->flags |= FPU_KERN_CTX_FPUINITDONE;
	fpuexit(td);
	ctx->prev = pcb->pcb_save;
	pcb->pcb_save = fpu_kern_ctx_savefpu(ctx);
	set_pcb_flags(pcb, PCB_KERNFPU);
	clear_pcb_flags(pcb, PCB_FPUINITDONE);
	critical_exit();
}

int
fpu_kern_leave(struct thread *td, struct fpu_kern_ctx *ctx)