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bootother.S 1.73 KiB
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#include "memlayout.h"
# Each non-boot CPU ("AP") is started up in response to a STARTUP
# IPI from the boot CPU.  Section B.4.2 of the Multi-Processor
# Specification says that the AP will start in real mode with CS:IP
# set to XY00:0000, where XY is an 8-bit value sent with the
# STARTUP. Thus this code must start at a 4096-byte boundary.
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#
# Because this code sets DS to zero, it must sit
# at an address in the low 2^16 bytes.
#
# Bootothers (in main.c) sends the STARTUPs one at a time.
# It copies this code (start) at 0x7000.
# It puts the address of a newly allocated per-core stack in start-4,
# and the address of the place to jump to (mpmain) in start-8.
#
# This code is identical to bootasm.S except:
#   - it does not need to enable A20
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#   - it uses the address at start-4 for the %esp
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#   - it jumps to the address at start-8 instead of calling bootmain
  xorw    %ax,%ax
  movw    %ax,%ds
  movw    %ax,%es
  movw    %ax,%ss
  lgdt    gdtdesc
  movl    %cr0, %eax
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  orl     $CR0_PE, %eax
  movl    %eax, %cr0
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//PAGEBREAK!
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  ljmpl    $(SEG_KCODE<<3), $(start32+KERNBASE)
start32:
  movw    $(SEG_KDATA<<3), %ax
  movw    %ax, %ds
  movw    %ax, %es
  movw    %ax, %ss
  movw    $0, %ax
  movw    %ax, %fs
  movw    %ax, %gs
  # switch to the stack allocated by bootothers()
  movl    P2V_WO(start-4), %esp
  call	*(P2V_WO(start)-8)
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  movw    $0x8a00, %ax
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  movw    %ax, %dx
  outw    %ax, %dx
  movw    $0x8ae0, %ax
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  outw    %ax, %dx
spin:
  jmp     spin
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  SEG_ASM(STA_X|STA_R, -KERNBASE, 0xffffffff)
  SEG_ASM(STA_W, -KERNBASE, 0xffffffff)

  .word   (gdtdesc - gdt - 1)
  .long   gdt