Ramdrive address

[Robert]

Hi!

How can I set the ramdrive's memory address?
Using QEMU without grub or grub on an actual machine.

[iansjack]

What ramdrive are you talking about?

[Robert]

What ramdrive are you talking about?

I'm developing my own OS and it is an initrd-like ramdrive.

[bzt]

Hi!

How can I set the ramdrive's memory address?
Using QEMU without grub or grub on an actual machine.

If I'm guessing right, you're using GRUB's module feature to load the ramdisk. In that case you cannot set the address, you must query it dynamically from GRUB's structures. First, get mods_addr from multiboot_info, and use it as a pointer to multiboot_module_t. Then from that struct, get mod_start, that will be your ramdisk's address (assuming your have only one module and that's your ramdisk).

Code: Select all

uint32_t ramdisk_addr = ((multiboot_module_t*)multiboot_info.mods_addr)->mod_start;

I also load the ramdisk as a GRUB module in my boot loader (that is, if you use it in Multiboot compatibility mode), here's the source (Assembly).

Cheers,
bzt

[Robert]

Set the address, not get. I wanted to load the image to a fixed address, no matter how large is the kernel image. But I solved the issue another way (memory reordering).

[austanss]

Set the address, not get. I wanted to load the image to a fixed address, no matter how large is the kernel image. But I solved the issue another way (memory reordering).

Then simply map the ramdrive addresses to a specific address in virtual address space.