🚀 go-pugleaf

Donald K. Forbes (don@mythos.com) wrote:
: ewirtz@bga.com (Erik Wirtz) wrote:

: >I am trying to convert a program that accesses a network card
: >to 32bit Protected mode.  It consists of a small C program and a 
: >small ASM program,  It works flawlessly in real mode.  When compiled
: >under 32bit Protected Mode it generates GP's.  I need help getting

: My guess is you are trying to access memory using a real mode 
: segment/offset pair.  You can not do this from protected mode.
: You must allocate a selector and set its base address and limit.

: In Windows 16 bit or Borland 16 bit DPMI you can use 
: AllocSelector(), SetSelectorBase() and SetSelectorLimit().
: but since your are using Borland 32 bit DPMI these are not
: available, therefore, you must call DPMI yourself.  If you
: do this, though, your program will not run in a DOS shell
: under Windows 95 (it will if you use 16 bit DPMI).  Here is
: some code that will allocate a selector and set its base/limit:

: /**************************************************************************
: *
: * Allocates a selector with base addres 'dwBaseAddress' and limit of
: * 'dwLimit'.  The return value is the new selector if the function is 
: * successful or 0 on failure.
: * 
: * This is function should not be confused with the Windows API
: function
: * of the same name which simply allocates a selector.
: *
:  ********************************************/
: SELECTOR _EXPORT AllocSelector(DWORD dwBaseAddress, DWORD dwLimit)
: {
:   SELECTOR selNew;

:   asm {
:     // dwLimit must be non-zero
:     mov   eax, dwLimit
:     or    eax, eax
:     jz    short Fail
:   
:     // Allocate a data selector (DPMI sets default acces rights)
:     mov   ax, 0x0000
:     mov   cx, 0x0001
:     int   DPMI_INT
:     jc    short Fail
:     mov   selNew, ax

:     // Set the selector's base address
:     mov   ax, 0x0007
:     mov   bx, selNew
:     mov   ecx, dwBaseAddress
:     mov   dx, cx
:     shr   ecx, 16
:     int   DPMI_INT
:     jc    short Fail

:     // Set the selector's limit
:     mov   ax, 0x0008
:     mov   bx, selNew
:     mov   ecx, dwLimit
:     dec   ecx
:     mov   dx, cx
:     shr   ecx, 16
:     int   DPMI_INT
:     jc    short Fail
:   }
: Success:
:   return selNew;
: Fail:
:   return 0;
: } 

: ------------------------------------------------------------
: Donald K. Forbes                     e-mail:  don@mythos.com
:             _  _     ____     ___ ___
:            / / //__/  /  /__//  //__
:           /   /  /   /  /  //__/___/ Software, Inc.

: My opinions are mine and not necessarily that of my employer
: ------------------------------------------------------------