Question for page

[xuanplus]

When I go to long mode like the first edition and try to write something to framebuffer, the qemu just reboot again and again with a page fault.

By searching, it happended for page map error.

The start address of buffer is 0xfd000000.

So, I just do identify map for 0~5G (maybe?) like this , it works well, but I don't think it is a good method.

...
set_up_page_tables:
        ; map first P4 entry to P3 table
        mov     eax,            p3_table
        or      eax,            0b11    ; present + writable
        mov     [p4_table],     eax

        ; map first five P3 entries to P2 table
        mov     eax,            p2_table + 0x1000 * 0
        or      eax,            0b11
        mov     [p3_table],     eax

        mov     eax,            p2_table + 0x1000 * 1
        or      eax,            0b11
        mov     [p3_table+8], eax

        mov     eax,            p2_table + 0x1000 * 2
        or      eax,            0b11
        mov     [p3_table+16],  eax

        mov     eax,            p2_table + 0x1000 * 3
        or      eax,            0b11
        mov     [p3_table+24],  eax

        mov     eax,            p2_table + 0x1000 * 4
        or      eax,            0b11
        mov     [p3_table+32],  eax

        ; map each P2 entry to a huge 2MiB page
        mov ecx, 0      ; counter variable
...

Please tell me a better solution