source: mainline/kernel/arch/sparc64/src/start.S@ e7b7be3f

#
# 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.
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#   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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# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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#include <arch/arch.h>
#include <arch/regdef.h>
#include <arch/boot/boot.h>
#include <arch/stack.h>

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

#ifdef CONFIG_SMP
#include <arch/context_offset.h>
#endif

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

.section K_TEXT_START, "ax"

#define BSP_FLAG        1

/*
 * Here is where the kernel is passed control from the boot loader.
 * 
 * The registers are expected to be in this state:
 * - %o0 starting address of physical memory + bootstrap processor flag
 *      bits 63...1:    physical memory starting address / 2
 *      bit 0:          non-zero on BSP processor, zero on AP processors
 * - %o1 bootinfo structure address (BSP only)
 * - %o2 bootinfo structure size (BSP only)
 *
 * Moreover, we depend on boot having established the following environment:
 * - TLBs are on
 * - identity mapping for the kernel image
 */

.global kernel_image_start
kernel_image_start:
        mov BSP_FLAG, %l0
        and %o0, %l0, %l7                       ! l7 <= bootstrap processor?
        andn %o0, %l0, %l6                      ! l6 <= start of physical memory

        ! Get bits 40:13 of physmem_base.
        srlx %l6, 13, %l5
        sllx %l5, 13 + (63 - 40), %l5
        srlx %l5, 63 - 40, %l5                  ! l5 <= physmem_base[40:13]
        
        /*
         * Setup basic runtime environment.
         */

        wrpr %g0, NWINDOWS - 2, %cansave        ! set maximum saveable windows
        wrpr %g0, 0, %canrestore                ! get rid of windows we will
                                                ! never need again
        wrpr %g0, 0, %otherwin                  ! make sure the window state is
                                                ! consistent
        wrpr %g0, NWINDOWS - 1, %cleanwin       ! prevent needless clean_window
                                                ! traps for kernel

        wrpr %g0, 0, %tl                        ! TL = 0, primary context
                                                ! register is used

        wrpr %g0, PSTATE_PRIV_BIT, %pstate      ! disable interrupts and disable
                                                ! 32-bit address masking

        wrpr %g0, 0, %pil                       ! intialize %pil

        /*
         * Switch to kernel trap table.
         */
        sethi %hi(trap_table), %g1
        wrpr %g1, %lo(trap_table), %tba

        /* 
         * Take over the DMMU by installing 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

#ifdef CONFIG_VIRT_IDX_DCACHE
#define TTE_LOW_DATA(imm)       (TTE_CP | TTE_CV | TTE_P | LMA | (imm))
#else /* CONFIG_VIRT_IDX_DCACHE */
#define TTE_LOW_DATA(imm)       (TTE_CP | TTE_P | LMA | (imm))
#endif /* CONFIG_VIRT_IDX_DCACHE */

#define SET_TLB_DATA(r1, r2, imm) \
        set TTE_LOW_DATA(imm), %r1; \
        or %r1, %l5, %r1; \
        mov PAGESIZE_4M, %r2; \
        sllx %r2, TTE_SIZE_SHIFT, %r2; \
        or %r1, %r2, %r1; \
        mov 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_L | TTE_W)     ! 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, TTE_W)                     ! 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)
        mov 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
        mov 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)
        mov 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, TTE_L)             ! use non-global mapping
        stxa %g1, [%g0] ASI_ITLB_DATA_IN_REG            
        flush %g5

        ! enter nucleus - using context 0
        wrpr %g0, 1, %tl

        ! 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
        
        ! leave nucleus - using primary context, i.e. context 0
        wrpr %g0, 0, %tl

        brz %l7, 1f                             ! skip if you are not the bootstrap CPU
        nop

        /*
         * Save physmem_base for use by the mm subsystem.
         * %l6 contains starting physical address
         */
        sethi %hi(physmem_base), %l4
        stx %l6, [%l4 + %lo(physmem_base)]

        /*
         * Precompute kernel 8K TLB data template.
         * %l5 contains starting physical address bits [40:13]
         */
        sethi %hi(kernel_8k_tlb_data_template), %l4
        ldx [%l4 + %lo(kernel_8k_tlb_data_template)], %l3
        or %l3, %l5, %l3
        stx %l3, [%l4 + %lo(kernel_8k_tlb_data_template)]

        /*
         * Flush D-Cache.
         */
        call dcache_flush
        nop

        /*
         * So far, we have not touched the stack.
         * It is a good idea to set the kernel stack to a known state now.
         */
        sethi %hi(temporary_boot_stack), %sp
        or %sp, %lo(temporary_boot_stack), %sp
        sub %sp, STACK_BIAS, %sp

        sethi %hi(bootinfo), %o0
        call memcpy                             ! copy bootinfo
        or %o0, %lo(bootinfo), %o0

        call arch_pre_main
        nop
        
        call main_bsp
        nop

        /* Not reached. */

0:
        ba 0b
        nop


        /*
         * Read MID from the processor.
         */
1:
        ldxa [%g0] ASI_UPA_CONFIG, %g1
        srlx %g1, UPA_CONFIG_MID_SHIFT, %g1
        and %g1, UPA_CONFIG_MID_MASK, %g1

#ifdef CONFIG_SMP
        /*
         * Active loop for APs until the BSP picks them up. A processor cannot
         * leave the loop until the global variable 'waking_up_mid' equals its
         * MID.
         */
        set waking_up_mid, %g2
2:
        ldx [%g2], %g3
        cmp %g3, %g1
        bne 2b
        nop

        /*
         * Configure stack for the AP.
         * The AP is expected to use the stack saved
         * in the ctx global variable.
         */
        set ctx, %g1
        add %g1, OFFSET_SP, %g1
        ldx [%g1], %o6

        call main_ap
        nop

        /* Not reached. */
#endif
        
0:
        ba 0b
        nop


.section K_DATA_START, "aw", @progbits

/*
 * Create small stack to be used by the bootstrap processor. It is going to be
 * used only for a very limited period of time, but we switch to it anyway,
 * just to be sure we are properly initialized.
 */

#define INITIAL_STACK_SIZE      1024

.align STACK_ALIGNMENT
        .space INITIAL_STACK_SIZE
.align STACK_ALIGNMENT
temporary_boot_stack:
        .space STACK_WINDOW_SAVE_AREA_SIZE


.data

.align 8
.global physmem_base            ! copy of the physical memory base address
physmem_base:
        .quad 0

/*
 * This variable is used by the fast_data_MMU_miss trap handler. In runtime, it
 * is further modified to reflect the starting address of physical memory.
 */
.global kernel_8k_tlb_data_template
kernel_8k_tlb_data_template:
#ifdef CONFIG_VIRT_IDX_DCACHE
        .quad ((1 << TTE_V_SHIFT) | (PAGESIZE_8K << TTE_SIZE_SHIFT) | TTE_CP | \
                 TTE_CV | TTE_P | TTE_W)
#else /* CONFIG_VIRT_IDX_DCACHE */
        .quad ((1 << TTE_V_SHIFT) | (PAGESIZE_8K << TTE_SIZE_SHIFT) | TTE_CP | \
                TTE_P | TTE_W)
#endif /* CONFIG_VIRT_IDX_DCACHE */