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[SOLVED] - Doubts when building libgcc -mcmodel=kernel
https://forum.osdev.org/viewtopic.php?f=1&t=33534		 Page 1 of 1
Author:  remizero [ Mon Feb 25, 2019 10:07 pm ]
Post subject:  [SOLVED] - Doubts when building libgcc -mcmodel=kernel
Hi, I'm new to the community. I'm taking my first steps in the study and development of an OS.
In the readings of the osdev wiki there is something that is not clear to me in the Building libgcc for mcmodel=kernel https://wiki.osdev.org/Building_libgcc_for_mcmodel%3Dkernel.

The question I have is:
   I have to build two libgcc?
   If I have to do this, then I have to build two gcc?
   If this is so, do I have to build two binutils?

On the other hand, from what I have understood so far:
   -mcmodel=kernel, as its name implies is used for kernel's compilation?
   -mcmodel=large is used for compilations of user mode applications?
   in both cases they are used to make compilations for different objective platforms. Right?

Thanks in advance for your answers.
Author:  Octocontrabass [ Tue Feb 26, 2019 5:17 am ]
Post subject:  Re: Doubts when building libgcc -mcmodel=kernel
remizero wrote:
I have to build two libgcc?

Yes, but I think you can use the multilib system to do it. The documentation for that is here and a guide for setting it up is here.

remizero wrote:
If I have to do this, then I have to build two gcc?

If you use multilib, you only need one GCC. Otherwise, you'll have to build two.

remizero wrote:
If this is so, do I have to build two binutils?

No.

remizero wrote:
-mcmodel=kernel, as its name implies is used for kernel's compilation?

It's used for higher-half kernels, where all code and statically-allocated data is in the highest 2GB of the virtual address space. If your kernel is not located there, you must use a different memory model.

remizero wrote:
-mcmodel=large is used for compilations of user mode applications?

It can be, but it's only really useful if you need more than 2GB of address space for your code and static data. The generated code is slightly less efficient, too. The default -mcmodel=small works best in most cases.

remizero wrote:
in both cases they are used to make compilations for different objective platforms. Right?

I don't understand the question. What is an "objective platform"?
Author:  Schol-R-LEA [ Wed Feb 27, 2019 12:37 pm ]
Post subject:  Re: Doubts when building libgcc -mcmodel=kernel
Octocontrabass wrote:
remizero wrote:
remizero wrote:
in both cases they are used to make compilations for different objective platforms. Right?

I don't understand the question. What is an "objective platform"?


I believe remizero means 'objective' in the sense of 'goal', here, not in the sense of 'not subjective', so 'target platform' would be the more typical wording.
Author:  remizero [ Wed Feb 27, 2019 8:26 pm ]
Post subject:  Re: Doubts when building libgcc -mcmodel=kernel
Thanks for such a quick response.

Exactly that's what I meant Schol-R-LEA, sorry for my poor English :(
What I meant was target platform, but it does not matter anymore, your explanation has been a great help to move forward and clear doubts.

But now the next question arises.

Working even from my host system, then I would not need another gcc to compile applications in user space, right?

therefore the question of whether to build two gcc
Author:  Octocontrabass [ Thu Feb 28, 2019 6:38 am ]
Post subject:  Re: Doubts when building libgcc -mcmodel=kernel
remizero wrote:
Working even from my host system, then I would not need another gcc to compile applications in user space, right?

That's right.
Author:  remizero [ Sat Mar 02, 2019 6:13 pm ]
Post subject:  Re: [SOLVED] - Doubts when building libgcc -mcmodel=kernel
Thanks for a lot
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