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Old 05-25-2018, 04:49 PM   #1
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fastest/easiest way to recompile simple module inside source tree?


Ive build my own kernel with some modifications, now I need to change some parts of a single module. How to recompile only this one without building the whole kernel?
Old 05-25-2018, 04:58 PM   #2
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You could go down the source tree to that module and use the Makefile to build it there. And insmod it from there. Otherwise if you kept the build files (did not make clean), with things like ccache in place, it wont take much time to rebuild the kernel through normal routes. Installing the new module is the hard part if you choose the former. A lot of which requires root permissions since it's the kernel.
Old 05-25-2018, 08:11 PM   #3
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I think you have to run depmod last thing if you build just the module.
Old 05-28-2018, 08:51 AM   #4
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I cant get the makefile inside the mouse-driver directory to work for me, but currently Iam doing a "make modules" in the root of the source-tree, which seems to only rebuild the changed module. But still takes a couple of seconds to check the other 1500 modules in the build.

After that I copy the regarding .ko file into the corresponding lib/modules directory and then rmmod and modprobe.
Old 05-28-2018, 09:05 AM   #5
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So what's the problem ?. Takes a few seconds as you say.
Old 05-28-2018, 09:44 AM   #6
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153 seconds, to be exactly. Raspberry Pi 3B+ and no cross-compile capable machine around here.

Last edited by Poison Nuke; 05-28-2018 at 09:52 AM.
Old 06-03-2018, 11:34 PM   #7
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is there such a thing as "simple kernel module" when the rest of the tree is involved?

the fact is there's always a chance that re-using ".o" from a previous build may not work

if your assembler (and compiler) are perfect in a perfect world you won't have problems

the problem is people can spend hours debugging things only to find the assembler is putting in "the wrong instructions" causing STALE ".o" to not work

if you knew the junk GCC and ASM did when translating C code to machine code you'd have a headache. it's not like the old days when things were "more pure" and there was a strong relation between C code and the underlying ASM code

for example: you might say "INC CX" in asm. you might write C code known to do exactly that given the surrounding code (if you know what your doing).

but today's compilers will look at your "arch" and add and remove ASM code in a highly speculative manner to "use the processor better". doing that changes the code size. you have a speculative linker to worry about to. the result: you link a new to an old and they depend on different holes - the "true" dependencies of physical time and space are not met, the program may crash or have an extremely difficult bug to find.

you'd expect that from a high level language. but hackers didn't care about purity.

you'd say: hey if i wanted ASM bloat added I would call C functions from a library like STDIO that provided wrapped services.

ah! that's where you'd be wrong. they are going to force you to use their ASM code, their idea of speculative cascasing memory permissions, their idea about everthing: in every language, below the root before you get the compiler

Last edited by X-LFS-2010; 06-03-2018 at 11:56 PM.


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