Function fpuinitstate

freebsd/amd64/amd64/fpu.c:433–496

* On the boot CPU we generate a clean state that is used to * initialize the floating point unit when it is first used by a * process. */

 * process.
 */
static void
fpuinitstate(void *arg __unused)
{
	uint64_t *xstate_bv;
	register_t saveintr;
	int cp[4], i, max_ext_n;

	/* Do potentially blocking operations before disabling interrupts. */
	fpu_save_area_zone = uma_zcreate("FPU_save_area",
	    cpu_max_ext_state_size, NULL, NULL, NULL, NULL,
	    XSAVE_AREA_ALIGN - 1, 0);
	fpu_initialstate = uma_zalloc(fpu_save_area_zone, M_WAITOK | M_ZERO);
	if (use_xsave) {
		max_ext_n = flsl(xsave_mask);
		xsave_area_desc = malloc(max_ext_n * sizeof(struct
		    xsave_area_elm_descr), M_DEVBUF, M_WAITOK | M_ZERO);
	}

	saveintr = intr_disable();
	stop_emulating();

	fpusave_fxsave(fpu_initialstate);
	if (fpu_initialstate->sv_env.en_mxcsr_mask)
		cpu_mxcsr_mask = fpu_initialstate->sv_env.en_mxcsr_mask;
	else
		cpu_mxcsr_mask = 0xFFBF;

	/*
	 * The fninit instruction does not modify XMM registers or x87
	 * registers (MM/ST).  The fpusave call dumped the garbage
	 * contained in the registers after reset to the initial state
	 * saved.  Clear XMM and x87 registers file image to make the
	 * startup program state and signal handler XMM/x87 register
	 * content predictable.
	 */
	bzero(fpu_initialstate->sv_fp, sizeof(fpu_initialstate->sv_fp));
	bzero(fpu_initialstate->sv_xmm, sizeof(fpu_initialstate->sv_xmm));

	/*
	 * Create a table describing the layout of the CPU Extended
	 * Save Area.
	 */
	if (use_xsave) {
		xstate_bv = (uint64_t *)((char *)(fpu_initialstate + 1) +
		    offsetof(struct xstate_hdr, xstate_bv));
		*xstate_bv = XFEATURE_ENABLED_X87 | XFEATURE_ENABLED_SSE;

		/* x87 state */
		xsave_area_desc[0].offset = 0;
		xsave_area_desc[0].size = 160;
		/* XMM */
		xsave_area_desc[1].offset = 160;
		xsave_area_desc[1].size = 288 - 160;

		for (i = 2; i < max_ext_n; i++) {
			cpuid_count(0xd, i, cp);
			xsave_area_desc[i].offset = cp[1];
			xsave_area_desc[i].size = cp[0];