VirtualBox

Changes between Initial Version and Version 1 of Ticket #20625, comment 14


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Timestamp:
12/30/2021 01:57:21 AM (12 months ago)
Author:
bird
Comment:

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  • Ticket #20625, comment 14

    initial v1  
    11As mentioned, TESTCFG.SYS ends up causing a BIOS call in real mode.  When switch to real mode an identity mapped page virtual address 12000h is installed by tweaking the page directory / tables.  When returning to protected mode, these page table and page directory changes are undone after enabling paging, but no CR3 flushing is done afterwards and that's causing trouble. 
    22{{{ 
    3 VBoxDbg> u 1200:00000147 L 60 
    4 1200:00000147 6a 01                   push byte 00001h 
    5 1200:00000149 9c                      pushfw 
    6 1200:0000014a 60                      pushaw 
    7 1200:0000014b 66 50                   push eax 
    8 1200:0000014d 66 53                   push ebx 
    9 1200:0000014f fa                      cli 
    10 1200:00000150 e9 bf fe                jmp -00141h (00012h) 
     3VBoxDbg> u 1200:00000153 L 60 
    1141200:00000153 55                      push bp 
    1251200:00000154 8b ec                   mov bp, sp 

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