Search found 387 matches

by Andyhhp
Tue Oct 30, 2012 1:22 am
Forum: Beginning OS Development
Topic: Bootloader instructions help
Replies: 3
Views: 8371

Re: Bootloader instructions help

In addition why do we need to null ds and es? ds and es are used implicitly by several common operations which we would want to perform during boot. In the example given, we are getting our running system into a consistant state. Depending on your nasm settings (the ORG statement), the chances are ...
by Andyhhp
Fri Sep 28, 2012 8:18 pm
Forum: Beginning OS Development
Topic: Combining C and Assembly for the bootloader
Replies: 3
Views: 8821

Re: Combining C and Assembly for the bootloader

You will get errors because you are delaring an extern variable but not linking.

As a result, nasm cant work out where that jump is supposed to go, so cant make a valid executable.

~Andrew
by Andyhhp
Tue Jul 31, 2012 10:29 pm
Forum: Advanced OS Development
Topic: [Example] Heap Manager for brokenthorn
Replies: 8
Views: 29734

Re: [Example] Heap Manager for brokenthorn

D'oh - I have been doing C89 for so long that without syntax highlighting, i completely missed the fact that that was a declaration rather than just another line of code.

~Andrew
by Andyhhp
Mon Jul 30, 2012 11:07 pm
Forum: Advanced OS Development
Topic: [Example] Heap Manager for brokenthorn
Replies: 8
Views: 29734

Re: [Example] Heap Manager for brokenthorn

If you are looking for some constructive criticism: Your #defines at the top should have the 'U' suffix to imply unsigned. It changes the behaviour of the arithmatic in certain places. Change HmmHeader to be more like this: typedef struct HmmHeader { uint32_t addr; HmmHeader *next; uint32_t allocate...
by Andyhhp
Sat May 12, 2012 7:34 pm
Forum: Beginning OS Development
Topic: memory size calculation from multiboot
Replies: 4
Views: 9677

Re: memory size calculation from multiboot

Virtual environments tend not to have an MMIO hole at 15 MB because it is not backed by the legacy hardware which requires it. As for your specific example, I would say that the number is simply being reported wrongly; The only way virtual environments want to communicate RAM information is throug t...
by Andyhhp
Thu May 10, 2012 11:10 pm
Forum: Beginning OS Development
Topic: memory size calculation from multiboot
Replies: 4
Views: 9677

Re: memory size calculation from multiboot

I would agree that that calculation looks wrong. However, the information in the multiboot header is advisory only, and even then only gives you the available memory up to the first MMIO hole which is typically at 15MB for compatability. Realistically, the only way to accuratly determine the extent ...
by Andyhhp
Sat Apr 28, 2012 12:23 pm
Forum: Beginning OS Development
Topic: higher half kernel and identity-mapping
Replies: 6
Views: 11819

Re: higher half kernel and identity-mapping

The problem is that BIOS service routines can not be used in 32bit mode, which means that when the bootloader jumps into 32bit mode, it can no longer load anything from disk without a proper scsi driver.
by Andyhhp
Fri Apr 27, 2012 8:49 pm
Forum: Beginning OS Development
Topic: higher half kernel and identity-mapping
Replies: 6
Views: 11819

Re: higher half kernel and identity-mapping

It is certainly possible to use memory above the 1Mb limit in Real mode. This is known as Unreal Mode, and works because of a quirk with how the segment registers work in 32bit mode. In 32bit mode, a lot of information is cached in non-accessable bits in the CPU. This saves the CPU needing to repeat...
by Andyhhp
Wed Feb 22, 2012 9:37 pm
Forum: News Discussion
Topic: OSDev Series: IA32 machine language
Replies: 7
Views: 45812

Re: OSDev Series: IA32 machine language

Hey, Sorry to call you out on this, but IA64 is the Intel Itanium architecture, not 64bit x86 archtecture. The naming is very confusing. 32bit: x86 (most common name) IA-32 (Intel name - default in their manuals) i386 (Linux 32bit stuff, including systems code) i686 (Linux 32bit kernel level stuff) ...
by Andyhhp
Sun Jan 01, 2012 11:30 pm
Forum: Lounge
Topic: Happy new year...
Replies: 5
Views: 27858

Re: Happy new year...

And a somewhat belated Happy New Year from me.

(Internetless at the time)

~Andrew
by Andyhhp
Wed Dec 28, 2011 10:02 pm
Forum: Advanced OS Development
Topic: copy, move in command promp
Replies: 8
Views: 15869

Re: copy, move in command promp

Copy and Move are very simple when thinking about what they are actually doing. With copy, you want to duplicate the data into another file. So, your copy program needs to open 1 file for reading, and create a new file for writing. Then just loop reading data from 1 file and writing it to the other,...
by Andyhhp
Tue Dec 27, 2011 10:09 pm
Forum: Advanced OS Development
Topic: copy, move in command promp
Replies: 8
Views: 15869

Re: copy, move in command promp

Ah - I misread you question. You can ignore about clipboards for your purposes, although they most certainly are not just a gui concept. a simple command line mv is trivial if you have a filesystem driver and some standard library functions for accessing the filesystem driver. If you lack those, the...
by Andyhhp
Mon Dec 26, 2011 4:11 pm
Forum: Advanced OS Development
Topic: copy, move in command promp
Replies: 8
Views: 15869

Re: copy, move in command promp

First of all, you need a clipboard. It doesn't nesseserally have to be in the kernel, but it does need to be system wide accessable. You need to have an API to read, write and clear the clipboard. Then, your command prompt keystroke interpreter should recognise certain keystoke combinations and use ...
by Andyhhp
Mon Dec 12, 2011 10:05 am
Forum: Beginning OS Development
Topic: Booting from disks with partitions other than FAT 12
Replies: 1
Views: 7336

Re: Booting from disks with partitions other than FAT 12

The FAT12/16/32 spec is available as a .doc from the Microsoft Website, or look on http://www.ntfs.com/#fat%20file%20system

However, on a floppy disk, you really want to be using FAT12 as it has less filesystem overhead, meaning you can store more regular data on the data.

~Andrew
by Andyhhp
Tue Nov 15, 2011 7:32 pm
Forum: Site Comments, Suggestions, and Ideas
Topic: Spam
Replies: 5
Views: 15038

Re: Spam

I had noticed that it had got substantially better recently.

Thanks,

~Andrew