[OpenBIOS] Re: [fb-d] Mixing 16 and 32 bits code

[Johan Rydberg]

Ollie Lho wrote:
> Ronald,
>         It seems that you made some mistake in mixing 16
> and 32 bits code in the intel_start32.S:
>
> _realstart:
>         cli
>         movw    %cs, %eax
>         movw    %eax, %es
>     xor  %eax, %eax
>     mov  %eax, %cr3    /* Invalidate TLB*/
>
>     .byte 0x66 /* prefix */
>     .byte 0x26
>     .byte 0x0f, 0x01, 0x16 /* lgdt [es:offset]*/
>     .word 0x02      /* offset in segment */
>
>     movl    %cr0, %eax
>     andl    $0x7FFAFFD1, %eax    /* PG,AM,WP,NE,TS,EM,MP = 0*/
>     orl     $1, %eax
>     movl    %eax, %cr0
>     data32
>     ljmp    $0x10, $.Lprotected
>
> Before _realstart there was a .code16 directive, so it should be in 16
> bits mode, so how could those 32 bits (long) operation works ??

The compiler (assembler) adds 32-bit prefix to the insn.