/*      $NetBSD: i386func.S,v 1.22 2020/05/19 21:40:55 ad Exp $ */

/*-
 * Copyright (c) 1998, 2007, 2008 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Charles M. Hannum, and by Andrew Doran.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Functions to provide access to i386-specific instructions.
 *
 * These are _not_ shared with NetBSD/xen.
 */

#include <machine/asm.h>
__KERNEL_RCSID(0, "$NetBSD: i386func.S,v 1.22 2020/05/19 21:40:55 ad Exp $");

#include <machine/specialreg.h>
#include <machine/segments.h>

#include "assym.h"

ENTRY(invlpg)
        movl    4(%esp), %eax
        invlpg  (%eax)
        ret
END(invlpg)

ENTRY(lldt)
        movl    4(%esp), %eax
        cmpl    %eax, CPUVAR(CURLDT)
        jne     1f
        ret
1:
        movl    %eax, CPUVAR(CURLDT)
        lldt    %ax
        ret
END(lldt)

ENTRY(ltr)
        movl    4(%esp), %eax
        ltr     %ax
        ret
END(ltr)

/*
 * Big hammer: flush all TLB entries, including ones from PTE's
 * with the G bit set.  This should only be necessary if TLB
 * shootdown falls far behind.
 *
 * Intel Architecture Software Developer's Manual, Volume 3,
 *      System Programming, section 9.10, "Invalidating the
 * Translation Lookaside Buffers (TLBS)":
 * "The following operations invalidate all TLB entries, irrespective
 * of the setting of the G flag:
 * ...
 * "(P6 family processors only): Writing to control register CR4 to
 * modify the PSE, PGE, or PAE flag."
 *
 * (the alternatives not quoted above are not an option here.)
 *
 * If PGE is not in use, we reload CR3.  Check for the PGE feature
 * first since i486 does not have CR4.  Note: the feature flag may
 * be present while the actual PGE functionality not yet enabled.
 */
ENTRY(tlbflushg)
        testl   $CPUID_PGE, _C_LABEL(cpu_feature)
        jz      1f
        movl    %cr4, %eax
        testl   $CR4_PGE, %eax
        jz      1f
        movl    %eax, %edx
        andl    $~CR4_PGE, %edx
        movl    %edx, %cr4
        movl    %eax, %cr4
        ret
END(tlbflushg)

ENTRY(tlbflush)
1:
        movl    %cr3, %eax
        movl    %eax, %cr3
        ret
END(tlbflush)

ENTRY(wbinvd)
        wbinvd
        ret
END(wbinvd)

/*
 * void lgdt(struct region_descriptor *rdp);
 *
 * Load a new GDT pointer (and do any necessary cleanup).
 * XXX It's somewhat questionable whether reloading all the segment registers
 * is necessary, since the actual descriptor data is not changed except by
 * process creation and exit, both of which clean up via task switches.  OTOH,
 * this only happens at run time when the GDT is resized.
 */
ENTRY(lgdt)
        /* Reload the descriptor table. */
        movl    4(%esp), %eax
        lgdt    (%eax)
        /* Flush the prefetch queue. */
        jmp     1f
        nop
1:      /* Reload "stale" selectors. */
        movl    $GSEL(GDATA_SEL, SEL_KPL), %eax
        movl    %eax, %ds
        movl    %eax, %es
        movl    %eax, %gs
        movl    %eax, %ss
        movl    $GSEL(GCPU_SEL, SEL_KPL), %eax
        movl    %eax, %fs
        jmp     _C_LABEL(x86_flush)
END(lgdt)