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#
# Copyright (C) 2005 Jakub Jermar
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# - Redistributions of source code must retain the above copyright
#   notice, this list of conditions and the following disclaimer.
# - 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.
# - The name of the author may not be used to endorse or promote products
#   derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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
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# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#

#include <arch/regdef.h>
#include <arch/boot/boot.h>

#include <arch/mm/mmu.h>
#include <arch/mm/tlb.h>
#include <arch/mm/tte.h>

.register %g2, #scratch
.register %g3, #scratch
.register %g6, #scratch
.register %g7, #scratch

.section K_TEXT_START, "ax"

/*
 * Here is where the kernel is passed control
 * from the boot loader.
 * 
 * The registers are expected to be in this state:
 * - %o0 bootinfo structure address
 * - %o1 bootinfo structure size
 *
 * Moreover, we depend on boot having established the
 * following environment:
 * - TLBs are on
 * - identity mapping for the kernel image
 * - identity mapping for memory stack
 */

.global kernel_image_start
kernel_image_start:

    /*
     * Setup basic runtime environment.
     */

    flushw              ! flush all but the active register window
    wrpr %g0, 0, %tl        ! TL = 0, primary context register is used

    ! Disable interrupts and disable 32-bit address masking.
    rdpr %pstate, %g1
    and %g1, ~(PSTATE_AM_BIT|PSTATE_IE_BIT), %g1
    wrpr %g1, 0, %pstate

    wrpr %r0, 0, %pil       ! intialize %pil

    /*
     * Copy the bootinfo structure passed from the boot loader
     * to the kernel bootinfo structure.
     */
    mov %o1, %o2
    mov %o0, %o1
    set bootinfo, %o0
    call memcpy
    nop

    /*
     * Switch to kernel trap table.
     */
    set trap_table, %g1
    wrpr %g1, 0, %tba

    /* 
     * Take over the DMMU by installing global locked
     * TTE entry identically mapping the first 4M
     * of memory.
     *
     * In case of DMMU, no FLUSH instructions need to be
     * issued. Because of that, the old DTLB contents can
     * be demapped pretty straightforwardly and without
     * causing any traps.
     */

    wr %g0, ASI_DMMU, %asi

#define SET_TLB_DEMAP_CMD(r1, context_id) \
    set (TLB_DEMAP_CONTEXT<<TLB_DEMAP_TYPE_SHIFT) | (context_id<<TLB_DEMAP_CONTEXT_SHIFT), %r1
    
    ! demap context 0
    SET_TLB_DEMAP_CMD(g1, TLB_DEMAP_NUCLEUS)
    stxa %g0, [%g1] ASI_DMMU_DEMAP          
    membar #Sync

#define SET_TLB_TAG(r1, context) \
    set VMA | (context<<TLB_TAG_ACCESS_CONTEXT_SHIFT), %r1

    ! write DTLB tag
    SET_TLB_TAG(g1, MEM_CONTEXT_KERNEL)
    stxa %g1, [VA_DMMU_TAG_ACCESS] %asi         
    membar #Sync

#define SET_TLB_DATA(r1, r2, imm) \
    set TTE_L | TTE_CP | TTE_P | TTE_W | LMA | imm, %r1; \
    set PAGESIZE_4M, %r2; \
    sllx %r2, TTE_SIZE_SHIFT, %r2; \
    or %r1, %r2, %r1; \
    set 1, %r2; \
    sllx %r2, TTE_V_SHIFT, %r2; \
    or %r1, %r2, %r1;
    
    ! write DTLB data and install the kernel mapping
    SET_TLB_DATA(g1, g2, TTE_G)
    stxa %g1, [%g0] ASI_DTLB_DATA_IN_REG        
    membar #Sync
    
    /*
     * Now is time to take over the IMMU.
     * Unfortunatelly, it cannot be done as easily as the DMMU,
     * because the IMMU is mapping the code it executes.
     *
     * [ Note that brave experiments with disabling the IMMU
     * and using the DMMU approach failed after a dozen
     * of desparate days with only little success. ]
     *
     * The approach used here is inspired from OpenBSD.
     * First, the kernel creates IMMU mapping for itself
     * in context 1 (MEM_CONTEXT_TEMP) and switches to
     * it. Context 0 (MEM_CONTEXT_KERNEL) can be demapped
     * afterwards and replaced with the kernel permanent
     * mapping. Finally, the kernel switches back to
     * context 0 and demaps context 1.
     *
     * Moreover, the IMMU requires use of the FLUSH instructions.
     * But that is OK because we always use operands with
     * addresses already mapped by the taken over DTLB.
     */
    
    set kernel_image_start, %g7
    
    ! write ITLB tag of context 1
    SET_TLB_TAG(g1, MEM_CONTEXT_TEMP)
    set VA_DMMU_TAG_ACCESS, %g2
    stxa %g1, [%g2] ASI_IMMU
    flush %g7

    ! write ITLB data and install the temporary mapping in context 1
    SET_TLB_DATA(g1, g2, 0)         ! use non-global mapping
    stxa %g1, [%g0] ASI_ITLB_DATA_IN_REG        
    flush %g7
    
    ! switch to context 1
    set MEM_CONTEXT_TEMP, %g1
    stxa %g1, [VA_PRIMARY_CONTEXT_REG] %asi ! ASI_DMMU is correct here !!!
    flush %g7
    
    ! demap context 0
    SET_TLB_DEMAP_CMD(g1, TLB_DEMAP_NUCLEUS)
    stxa %g0, [%g1] ASI_IMMU_DEMAP          
    flush %g7
    
    ! write ITLB tag of context 0
    SET_TLB_TAG(g1, MEM_CONTEXT_KERNEL)
    set VA_DMMU_TAG_ACCESS, %g2
    stxa %g1, [%g2] ASI_IMMU
    flush %g7

    ! write ITLB data and install the permanent kernel mapping in context 0
    SET_TLB_DATA(g1, g2, 0)         ! use non-global mapping
    stxa %g1, [%g0] ASI_ITLB_DATA_IN_REG        
    flush %g7

    ! switch to context 0
    stxa %g0, [VA_PRIMARY_CONTEXT_REG] %asi ! ASI_DMMU is correct here !!!
    flush %g7

    ! ensure nucleus mapping
    wrpr %g0, 1, %tl

    ! set context 1 in the primary context register
    set MEM_CONTEXT_TEMP, %g1
    stxa %g1, [VA_PRIMARY_CONTEXT_REG] %asi ! ASI_DMMU is correct here !!!
    flush %g7

    ! demap context 1
    SET_TLB_DEMAP_CMD(g1, TLB_DEMAP_PRIMARY)
    stxa %g0, [%g1] ASI_IMMU_DEMAP          
    flush %g7
    
    ! set context 0 in the primary context register
    stxa %g0, [VA_PRIMARY_CONTEXT_REG] %asi ! ASI_DMMU is correct here !!!
    flush %g7
    
    ! set TL back to 0
    wrpr %g0, 0, %tl
    
    call main_bsp
    nop

    /* Not reached. */

2:
    b 2b
    nop