I know this might be a stupid newbie question but I cant help it, lol
I have been hearing alot about Dynamic linking, I just cant seem to figure out what it is, Can someone explain it to me?, thx
What is Dynamic Linking?
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Moose
RE:What is Dynamic Linking?
When i link my kernel, i have lots of object files that represent code. They all get placed inside one file when they are linked together. This is static linking.
Dynamic linking is loading an object file into a program 'on the fly' in real time. So it gets linked while the program is running.
Linux drivers are essentially elf object files. They are dynamically linked into the kernel when those drivers are needed. They are then unlinked when they are not needed.
Its sort of attaching another object to a progran, after you've linked the program for it to become executable.
Moose.
Dynamic linking is loading an object file into a program 'on the fly' in real time. So it gets linked while the program is running.
Linux drivers are essentially elf object files. They are dynamically linked into the kernel when those drivers are needed. They are then unlinked when they are not needed.
Its sort of attaching another object to a progran, after you've linked the program for it to become executable.
Moose.
RE:What is Dynamic Linking?
Seems intresting.. 
How do i write to to "link" in a extra (standard dos) .obj in my kernel?
In nasm code? Some links maybe?
Thanks.
/ Christoffer
How do i write to to "link" in a extra (standard dos) .obj in my kernel?
In nasm code? Some links maybe?
Thanks.
/ Christoffer
RE:What is Dynamic Linking?
Can someone explain how to do this?
/ Christoffer
/ Christoffer
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carbonBased
RE:What is Dynamic Linking?
It's not easy.
First, decide on your object format. For my OS, I dynamically load in RDOFF2 objects (aka, the format developed by the Nasm developers). It may not be as extensible as ELF (although it comes surprisingly close), but it's a simple format, and that rates highly in my books
Second, research this object file format thoroughly. As you do so, the concept of dynamic linking will probably start to make more sense.
Essentially, all you do is load the object into memory, and look at the object's header. The header will contain information about the object, like where each of the sections (.text, .code) are, and how much space should be reserved for the .bss section.
The header will also contain (more importantly) offsets into these sections that need to be 'fixed' In other words, these are variables, function pointers, etc, that are contained elsewhere... in other objects... or in your kernel. You'll have to go through all of these, and replace them with the proper offsets of the other objects/your kernel.
And lastly, the header will also contain a list of all the globally available symbols in the object. If you need any of these, you should record them somewhere, and perhaps 'fix'/patch your kernel with these addresses, if it needs them.
Hope that makes sense. Like I said, my kernel does this with RDOFF2 modules... it might help to see it in code: http://www.neuraldk.org (products -> ndk). The code's not beautiful, by any means... it's not done. But it works.
Cheers,
Jeff
First, decide on your object format. For my OS, I dynamically load in RDOFF2 objects (aka, the format developed by the Nasm developers). It may not be as extensible as ELF (although it comes surprisingly close), but it's a simple format, and that rates highly in my books
Second, research this object file format thoroughly. As you do so, the concept of dynamic linking will probably start to make more sense.
Essentially, all you do is load the object into memory, and look at the object's header. The header will contain information about the object, like where each of the sections (.text, .code) are, and how much space should be reserved for the .bss section.
The header will also contain (more importantly) offsets into these sections that need to be 'fixed' In other words, these are variables, function pointers, etc, that are contained elsewhere... in other objects... or in your kernel. You'll have to go through all of these, and replace them with the proper offsets of the other objects/your kernel.
And lastly, the header will also contain a list of all the globally available symbols in the object. If you need any of these, you should record them somewhere, and perhaps 'fix'/patch your kernel with these addresses, if it needs them.
Hope that makes sense. Like I said, my kernel does this with RDOFF2 modules... it might help to see it in code: http://www.neuraldk.org (products -> ndk). The code's not beautiful, by any means... it's not done. But it works.
Cheers,
Jeff