Need clearings about kernel headers

Hi all.

I need to know which differences are between the various kernel headers distributed with kernels.

Which version I should use? I was thinking that I must use the same version of the used kernel, but by this way I have problems compiling programs.

An example: I was trying to compile chillispot.
using kernel 2.4.31 and headers 2.4.31 compiled ok;
using kernel 2.6.11.11 and headers 2.4.31 compiled ok;
using kernel 2.6.11.11 and headers 2.6.11.11 I get an error
Here you can find more details

I'm using slack updated to current, and I was using precompiled kernels from slackware ftp.

I also read the readme/warning of the 2.6 headers, but it isn't too much clear.

Can anyone explain me something more to understand why I have problems with 2.6 headers?ù

Tnx all in advance

using kernel 2.4.31 and headers 2.4.31 compiled ok;

This is ok. the program will work.

using kernel 2.6.11.11 and headers 2.4.31 compiled ok;

This is not ok. the program will not work. The program does not check that the headers match the kernel, but even if it compiles, it won't run.

using kernel 2.6.11.11 and headers 2.6.11.11 I get an error

Maybe the program is only designed for a 2.4 kernel

but the program works perfectly under 2.6.x kernels ... it interacts strongly with kernel (it creates a TUN device which is similar to a virtual net interface) and it works flawlessy ....

I may not be 100% correct about this.
99% of Linux programs use glibc (http://www.gnu.org/software/libc/libc.html) to run, it's a C library which offers basic functions like allocating memory, opening files, etc.
The problem between different headers often arises when you compile that library with 2.4 headers, and then try to compile a program with 2.6 headers using the glibc library which was built against 2.4 headers.
I don't know exactly which code could break the program but as you can guess some functionality will be different in 2.4 and 2.6 kernels.
As Pat states in the warning file, not all code will break with different headers.
I hope I'm clear enough.

so probably (actual) glibc is compiled using 2.4 headers, and if I install 2.6 headers and I try to compile programs I get an error.
If I use 2.4 header (same as used to compile glibc) the conflict is resolved .. indipendently from the running kernel.

So using kernel 2.6 and headers 2.4 shouldn't be a mistake, unless libc 'becomes' compiled using 2.6 headers ..

Thanks for the clarification

Originally posted by Barx Which version I should use? I was thinking that I must use the same version of the used kernel, but by this way I have problems compiling programs.

This is to be expected. Your assumption that the headers must be the same version as the running kernel is incorrect. The kernel headers must match the headers used to compile glibc. Simply put, do not upgrade the kernel headers.

Originally posted by stefan_nicolau quote: using kernel 2.6.11.11 and headers 2.4.31 compiled ok; This is not ok. the program will not work. The program does not check that the headers match the kernel, but even if it compiles, it won't run.

This is wrong.

Originally posted by gbonvehi I may not be 100% correct about this.

Sounds 100% correct to me.

Originally posted by Barx So using kernel 2.6 and headers 2.4 shouldn't be a mistake, unless libc 'becomes' compiled using 2.6 headers ..

Exactly

Originally posted by Barx Thanks for the clarification

No problem

Originally posted by shilo Sounds 100% correct to me.

Thanks, I wasn't sure if I was explaining it ok and my programming/guessing skills were right

quote:Originally posted by stefan_nicolau quote: using kernel 2.6.11.11 and headers 2.4.31 compiled ok; This is not ok. the program will not work. The program does not check that the headers match the kernel, but even if it compiles, it won't run. This is wrong.

Sorry, I was thinking about compiling kernel modules.

Tnx all!

Last question: If I want to recompile kernel 2.6 and modules, which headers I should use? 2.4 as used to compile libc, or 2.6 as the kernel I'm compiling??

2.4 headers as libc

Last question:

I thought that was the first question?

Originally posted by shilo I thought that was the first question?

the first question was "Can anyone explain me something more to understand why I have problems with 2.6 headers?" :-)

Now is all clear, tnx all

So how would one recompile glibc with 2.6 headers?

Sounds like the chicken or the egg.

A search tool is a wonderful thing - perhaps start here

Barx, Chinaman quoted a good part of text about why the headers should match glibc here: http://www.linuxquestions.org/questi...61#post1723561
There's also a link to the original article there.