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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

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# - Redistributions in binary form must reproduce the above copyright

#   notice, this list of conditions and the following disclaimer in the

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# - The name of the author may not be used to endorse or promote products

#   derived from this software without specific prior written permission.

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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

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#

#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

.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 %g0, 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, 0)			! use non-global mapping

	stxa %g1, [%g0] ASI_DTLB_DATA_IN_REG		

	membar #Sync

	/*

	 * Because we cannot use global mappings (because we want to

	 * have separate 64-bit address spaces for both the kernel

	 * and the userspace), we prepare the identity mapping also in

	 * context 1. This step is required by the

	 * code installing the ITLB mapping.

	 */

	! write DTLB tag of context 1 (i.e. MEM_CONTEXT_TEMP)

	SET_TLB_TAG(g1, MEM_CONTEXT_TEMP)

	stxa %g1, [VA_DMMU_TAG_ACCESS] %asi			

	membar #Sync

	! write DTLB data and install the kernel mapping in context 1

	SET_TLB_DATA(g1, g2, 0)			! use non-global mapping

	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, %g5

	! 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 %g5

	! 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 %g5

	! switch to context 1

	set MEM_CONTEXT_TEMP, %g1

	stxa %g1, [VA_PRIMARY_CONTEXT_REG] %asi	! ASI_DMMU is correct here !!!

	flush %g5

	! demap context 0

	SET_TLB_DEMAP_CMD(g1, TLB_DEMAP_NUCLEUS)

	stxa %g0, [%g1] ASI_IMMU_DEMAP			

	flush %g5

	! 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 %g5

	! 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 %g5

	! switch to context 0

	stxa %g0, [VA_PRIMARY_CONTEXT_REG] %asi	! ASI_DMMU is correct here !!!

	flush %g5

	! 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 %g5

	! demap context 1

	SET_TLB_DEMAP_CMD(g1, TLB_DEMAP_PRIMARY)

	stxa %g0, [%g1] ASI_IMMU_DEMAP			

	flush %g5

	! set context 0 in the primary context register

	stxa %g0, [VA_PRIMARY_CONTEXT_REG] %asi	! ASI_DMMU is correct here !!!

	flush %g5

	! set TL back to 0

	wrpr %g0, 0, %tl

	call arch_pre_main

	nop

	call main_bsp

	nop

	/* Not reached. */

2:

	b 2b

	nop