Subversion Repositories Kolibri OS

align 4

proc user_unmap stdcall, base:dword, offset:dword, size:dword

        push    ebx

        mov     ebx, [base]             ; must be valid pointer

        test    ebx, ebx

        jz      .error

        mov     edx, [offset]           ; check offset

        add     edx, ebx                ; must be below 2Gb app limit

        js      .error

        shr     ebx, 12                 ; chek block attributes

        lea     ebx, [page_tabs+ebx*4]

        mov     eax, [ebx-4]            ; block attributes

        test    al, USED_BLOCK

        jz      .error

        test    al, DONT_FREE_BLOCK

        jnz     .error

        shr     edx, 12

        lea     edx, [page_tabs+edx*4]  ; unmap offset

        mov     ecx, [size]

        add     ecx, 4095

        shr     ecx, 12                 ; unmap size in pages

        shr     eax, 12                 ; block size + 1 page

        lea     ebx, [ebx+eax*4-4]      ; block end ptr

        lea     eax, [edx+ecx*4]        ; unmap end ptr

        cmp     eax, ebx                ; check for overflow

        ja      .error

        mov     ebx, [offset]

        and     ebx, not 4095           ; is it required ?

.unmap:

        mov     eax, [edx]              ; get page addres

        test    al, 1                   ; page mapped ?

        jz      @F

        test    eax, PG_SHARED          ; page shared ?

        jnz     @F

        mov     [page_tabs+edx*4], dword 2

                                        ; mark page as reserved

        invlpg  [ebx]                   ; when we start using

        call    free_page               ; empty c-o-w page instead this ?

@@:

        add     ebx, 4096

        add     edx, 4

        dec     ecx

        jnz     .unmap

        pop     ebx

        or      al, 1                   ; return non zero on success

        ret

.error:

        pop     ebx

        xor     eax, eax                ; something wrong

        ret

endp