Hello,

I am just doing some R&D regarding low level development with D. Due to the multiboot standard, and the weird things you have to do at bootup on the x86 architecture, one has to perform a far jump to a specific code segment given as an offset to the prior registered GDT. Now, with nasm/Intel syntax, you can just do:

/+ ... +/
jmp 0x08:flush

flush:
/+ ... +/

.. in D, my brain tells me, the syntax would theoretically look like this:

void flush ( )

    asm {
        naked;

        /+ ... +/
        jmp int far ptr 0x08:flush;

        flush:
            /+ ... +/

        ret;
    }
}

Yet, the compiler (1.009) yells at me, that either the operand size for `jmp` is wrong, or it would have expected nops instead of the jump statement.

Any advice one could give?

Thanks in advance, and best regards,
Alex

On Tue, 13 Mar 2007 05:24:44 +0100, Alexander Panek <alexander.panek@brainsware.org> wrote:
> [...]
> void flush ( )
>
>     asm {
>         naked;
>
>         /+ ... +/
>         jmp int far ptr 0x08:flush;
>
>         flush:
>             /+ ... +/
>
>         ret;
>     }
> }
> [...]

Scratch that `int`. It's meant to be a 48-bit address.

Alexander Panek wrote:
> I am just doing some R&D regarding low level development with D. Due to the
> multiboot standard, and the weird things you have to do at bootup on the x86
> architecture, one has to perform a far jump to a specific code segment given
> as an offset to the prior registered GDT.

This doesn't have much to do with the multiboot standard, just the x86 architecture. Multiboot just doesn't allow you to assume the GDT is already correctly loaded (though the segment registers will be).

> Now, with nasm/Intel syntax, you
> can just do:
> 
> /+ ... +/
> jmp 0x08:flush
> 
> flush:
> /+ ... +/
> 
> .. in D, my brain tells me, the syntax would theoretically look like this:
> 
> void flush ( )
> 
>     asm {
>         naked;
> 
>         /+ ... +/
>         jmp int far ptr 0x08:flush;
> 
>         flush:
>             /+ ... +/
> 
>         ret;
>     }
> }
> 
> Yet, the compiler (1.009) yells at me, that either the operand size for
> `jmp` is wrong, or it would have expected nops instead of the jump
> statement.
> 
> Any advice one could give?

Sorry, I have no idea how to do this in the D inline assembler. I just have an external .asm file that sets up the GDT (and rudimentary paging) before calling the D code. I prefer the NASM variation of asm syntax anyway.

On Tue, 13 Mar 2007 11:49:22 +0100, Frits van Bommel <fvbommel@REMwOVExCAPSs.nl> wrote:
> This doesn't have much to do with the multiboot standard, just the x86 architecture. Multiboot just doesn't allow you to assume the GDT is already correctly loaded (though the segment registers will be).

Yea, I've seen that after the second time of reading, too. X-P

> Sorry, I have no idea how to do this in the D inline assembler. I just have an external .asm file that sets up the GDT (and rudimentary paging) before calling the D code. I prefer the NASM variation of asm syntax anyway.

I do have an assembler file for exactly that, which I just try to translate to D code.