61 lines
1.7 KiB
ArmAsm
61 lines
1.7 KiB
ArmAsm
#include "asm.h"
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#include "memlayout.h"
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#include "mmu.h"
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# Each non-boot CPU ("AP") is started up in response to a STARTUP
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# IPI from the boot CPU. Section B.4.2 of the Multi-Processor
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# Specification says that the AP will start in real mode with CS:IP
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# set to XY00:0000, where XY is an 8-bit value sent with the
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# STARTUP. Thus this code must start at a 4096-byte boundary.
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#
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# Because this code sets DS to zero, it must sit
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# at an address in the low 2^16 bytes.
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#
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# Startothers (in main.c) sends the STARTUPs one at a time.
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# It copies this code (start) at 0x7000. It puts the address of
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# a newly allocated per-core stack in start-12,the address of the
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# place to jump to (apstart32) in start-4, and the physical address
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# of entrypgdir in start-12.
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.code16
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.globl start
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start:
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cli
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# Zero data segment registers DS, ES, and SS.
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xorw %ax,%ax
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movw %ax,%ds
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movw %ax,%es
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movw %ax,%ss
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# Switch from real to protected mode. Use a bootstrap GDT that makes
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# virtual addresses map directly to physical addresses so that the
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# effective memory map doesn't change during the transition.
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lgdt gdtdesc
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movl %cr0, %eax
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orl $CR0_PE, %eax
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movl %eax, %cr0
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# Complete the transition to 32-bit protected mode by using a long jmp
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# to reload %cs and %eip. The segment descriptors are set up with no
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# translation, so that the mapping is still the identity mapping.
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ljmpl $(SEG_KCODE32), $start32
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.code32
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start32:
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movl $start-12, %esp
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movl start-4, %ecx
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jmp *%ecx
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.align 4
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gdt:
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SEG_NULLASM
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SEG_ASM(0xa, 0, 0xffffffff)
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SEG_ASM(0x2, 0, 0xffffffff)
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.align 16
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gdtdesc:
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.word 0x17 # sizeof(gdt)-1
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.long gdt
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