cprocstart  InstallBankFunc        ARG     codeLen:UINT, bankFunc:DPTR        enter_c        mov     esi,[bankFunc]      ; Copy the code into buffer        mov     edi,offset BankFuncBuf        mov     ecx,[codeLen]    rep movsb        mov     [BYTE edi],0C3h     ; Terminate the function with a near ret        leave_c        retcprocend;----------------------------------------------------------------------------; int InitPaging(void);----------------------------------------------------------------------------; Initializes paging system. If paging is not enabled, builds a page table; directory and page tables for physical memory;;   Exit:       0   - Successful;               -1  - Couldn't initialize paging mechanism;----------------------------------------------------------------------------cprocstart  InitPaging        push    ebx        push    ecx        push    edx        push    esi        push    edi; Are we running under CauseWay?        mov     ax,0FFF9h        int     31h        jc      @@NotCauseway        cmp     ecx,"CAUS"        jnz     @@NotCauseway        cmp     edx,"EWAY"        jnz     @@NotCauseway        mov     [BOOL VF_haveCauseWay],1        mov     [CauseWayDIRLinear],esi        mov     [CauseWay1stLinear],edi; Check for DPMI        mov     ax,0ff00h        push    es        int     31h        pop     es        shr     edi,2        and     edi,3        cmp     edi,2        jz      @@ErrExit               ; Not supported under DPMI        mov     eax,[CauseWayDIRLinear]        jmp     @@CopyCR3@@NotCauseway:        mov     ax,cs        test    ax,3                    ; Which ring are we running        jnz     @@ErrExit               ; Needs zero ring to access                                        ; page tables (CR3)        mov     eax,cr0                 ; Load CR0        test    eax,80000000h           ; Is paging enabled?        jz      @@ErrExit               ; No, we must have paging!        mov     eax,cr3                 ; Load directory address        and     eax,0FFFFF000h@@CopyCR3:        mov     [PDBR],eax              ; Save it        mov     esi,eax        mov     edi,offset pageDirectory        mov     ecx,1024        cld        rep     movsd                   ; Copy the original page table directory        cmp     [DWORD accessPageAddr],0; Check if we have allocated page        jne     @@HaveRealMem           ; table already (we cant free it)        mov     eax,0100h               ; DPMI DOS allocate        mov     ebx,8192/16        int     31h                     ; Allocate 8192 bytes        and     eax,0FFFFh        shl     eax,4                   ; EAX points to newly allocated memory        add     eax,4095        and     eax,0FFFFF000h          ; Page align        mov     [accessPageAddr],eax@@HaveRealMem:        mov     eax,[accessPageAddr]    ; EAX -> page table in 1st Mb        shr     eax,12        and     eax,3FFh                ; Page table offset        shl     eax,2        cmp     [BOOL VF_haveCauseWay],0        jz      @@NotCW0        mov     ebx,[CauseWay1stLinear]        jmp     @@Put1st@@NotCW0:        mov     ebx,[PDBR]        mov     ebx,[ebx]        and     ebx,0FFFFF000h          ; Page table for 1st megabyte@@Put1st:        add     eax,ebx        mov     [accessPageTable],eax        sub     eax,eax                 ; No error        jmp     @@Exit@@ErrExit:        mov     eax,-1@@Exit: pop     edi        pop     esi        pop     edx        pop     ecx        pop     ebx        retcprocend;----------------------------------------------------------------------------; void ClosePaging(void);----------------------------------------------------------------------------; Closes the paging system;----------------------------------------------------------------------------cprocstart  ClosePaging        push    eax        push    ecx        push    edx        push    esi        push    edi        mov     eax,[accessPageAddr]        call    AccessPage              ; Restore AccessPage mapping        mov     edi,[PDBR]        mov     esi,offset pageDirectory        mov     ecx,1024        cld        rep     movsd                   ; Restore the original page table directory@@Exit: pop     edi        pop     esi        pop     edx        pop     ecx        pop     eax        retcprocend;----------------------------------------------------------------------------; long AccessPage(long phys);----------------------------------------------------------------------------; Maps a known page to given physical memory;   Entry:      EAX - Physical memory;   Exit:       EAX - Linear memory address of mapped phys mem;----------------------------------------------------------------------------cprocstatic     AccessPage        push    edx        mov     edx,[accessPageTable]        or      eax,7        mov     [edx],eax        mov     eax,cr3        mov     cr3,eax                 ; Update page table cache        mov     eax,[accessPageAddr]        pop     edx        retcprocend;----------------------------------------------------------------------------; long GetPhysicalAddress(long linear);----------------------------------------------------------------------------; Returns the physical address of linear address;   Entry:      EAX - Linear address to convert;   Exit:       EAX - Physical address;----------------------------------------------------------------------------cprocstatic     GetPhysicalAddress        push    ebx        push    edx        mov     edx,eax        shr     edx,22                  ; EDX is the directory offset        mov     ebx,[PDBR]        mov     edx,[edx*4+ebx]         ; Load page table address        push    eax        mov     eax,edx        call    AccessPage              ; Access the page table        mov     edx,eax        pop     eax        shr     eax,12        and     eax,03FFh               ; EAX offset into page table        mov     eax,[edx+eax*4]         ; Load physical address        and     eax,0FFFFF000h        pop     edx        pop     ebx        retcprocend;----------------------------------------------------------------------------; void CreatePageTable(long pageDEntry);----------------------------------------------------------------------------; Creates a page table for specific address (4MB);       Entry:  EAX - Page directory entry (top 10-bits of address);----------------------------------------------------------------------------cprocstatic     CreatePageTable        push    ebx        push    ecx        push    edx        push    edi        mov     ebx,eax                 ; Save address        mov     eax,8192        push    eax        call    VF_malloc              ; Allocate page table directory        add     esp,4        add     eax,0FFFh        and     eax,0FFFFF000h          ; Page align (4KB)        mov     edi,eax                 ; Save page table linear address        sub     eax,eax                 ; Fill with zero        mov     ecx,1024        cld        rep     stosd                   ; Clear page table        sub     edi,4096        mov     eax,edi        call    GetPhysicalAddress        mov     edx,[PDBR]        or      eax,7                   ; Present/write/user bit        mov     [edx+ebx*4],eax         ; Save physical address into page directory        mov     eax,cr3        mov     cr3,eax                 ; Update page table cache        pop     edi        pop     edx        pop     ecx        pop     ebx        retcprocend;----------------------------------------------------------------------------; void MapPhysical2Linear(ulong pAddr, ulong lAddr, int pages, int flags);;----------------------------------------------------------------------------; Maps physical memory into linear memory;   Entry:      pAddr   - Physical address;               lAddr   - Linear address;               pages   - Number of 4K pages to map;               flags   - Page flags;                           bit 0   =       present;                           bit 1   =       Read(0)/Write(1);----------------------------------------------------------------------------cprocstart  MapPhysical2Linear        ARG     pAddr:ULONG, lAddr:ULONG, pages:UINT, pflags:UINT        enter_c        and     [ULONG pAddr],0FFFFF000h; Page boundary        and     [ULONG lAddr],0FFFFF000h; Page boundary        mov     ecx,[pflags]        and     ecx,11b                 ; Just two bits        or      ecx,100b                ; Supervisor bit        mov     [pflags],ecx        mov     edx,[lAddr]        shr     edx,22                  ; EDX = Directory        mov     esi,[PDBR]        mov     edi,[pages]             ; EDI page count        mov     ebx,[lAddr]@@CreateLoop:        mov     ecx,[esi+edx*4]         ; Load page table address        test    ecx,1                   ; Is it present?        jnz     @@TableOK        mov     eax,edx        call    CreatePageTable         ; Create a page table@@TableOK:        mov     eax,ebx        shr     eax,12        and     eax,3FFh        sub     eax,1024        neg     eax                     ; EAX = page count in this table        inc     edx                     ; Next table        mov     ebx,0                   ; Next time we'll map 1K pages        sub     edi,eax                 ; Subtract mapped pages from page count        jns     @@CreateLoop            ; Create more tables if necessary        mov     ecx,[pages]             ; ECX = Page count        mov     esi,[lAddr]        shr     esi,12                  ; Offset part isn't needed        mov     edi,[pAddr]@@MappingLoop:        mov     eax,esi        shr     eax,10                  ; EAX = offset to page directory        mov     ebx,[PDBR]        mov     eax,[eax*4+ebx]         ; EAX = page table address        call    AccessPage        mov     ebx,esi        and     ebx,3FFh                ; EBX = offset to page table        mov     edx,edi        add     edi,4096                ; Next physical address        inc     esi                     ; Next linear page        or      edx,[pflags]            ; Update flags...        mov     [eax+ebx*4],edx         ; Store page table entry        loop    @@MappingLoop        mov     eax,cr3        mov     cr3,eax                 ; Update page table cache        leave_c        retcprocendendcodeseg  _vflatendif        END                     ; End of module