Paging? Crash!

[deleted]

Hey guys,

I have finally picked back up my OS (not even) again after a break. I scrapped the old one, and restarted from brandon's tutorial. I attempted to implements James Malloy's paging system, but to no avil.

I am using QEMU and i686-pc-elf toolchain, when I try to boot the OS, it won't get past the "Booting" message on QEMU. My code can be found here: https://github.com/BiggerOnTheInside/Boom

Any help would by greatly aprecated!

PS: James's (kmalloc && friends functions) = working!

[eryjus]

Hi,

You are not calling paging_install() -- it is commented out. Assuming that was a mistake to commit that code with the function call commented out, I would implement switch_page_directory() as pure assembly. Its current implementation will cause you quite a bit of trouble. I cannot comment on the details of the problems it causes because I stay away from inline assembly. However, you can disassemble your object (or compile to assembly) and compare that against what you intended in the C code and see how the compiler shoots you in the foot.

Now, if I remember correctly, I had all kinds of trouble with that tutorial and it took quite a while to work out the bugs -- if I even got them all. I would check the wiki for more details. You will be better to write your own paging code since you will understand it much better if you do.

[madanra]

If you haven't already, it's worth reading James Molloy's Tutorial Known Bugs on the wiki first.

[deleted]

Thanks guys, I got it working! I worked with the wiki's stuff, and it works! Thanks again

[deleted]

Ok, new problem. I tried to create a spot in physical memory using malloc() (From James's tutorial), here's what I did:

Code: Select all

char a = '1';
    char *b = malloc(sizeof(a));
    *b = a;
    char c = b;
    
    putch(c);

And it throws a page fault. Entire code is at http://github.com/BiggerOnTheInside/Boom/

Thanks

[Techel]

Maybe your pages after 'end' is not mapped or the problem is in the 'putch' function.

[deleted]

Stupid me! I cast (if possible [from Java background]) a char* to a char! Fixed it, error done.

Please excuse my n00bness

[deleted]

Hello,

Just to check, what does it mean if ASSERT fails when freeing memory? That is, in James's Malloy's tutorial.

Thanks!