如何在 raspbian 上修复一个奇怪的 linux kernel 模块构建问题，在 x64 上运行良好 ubuntu

Question

I ran into this problem and figured it out but it took me a while because it wasn't obvious, so I thought I'd post here to help out if anybody else has this problem.

I have a linux kernel module that I build on x86 and on a bunch of raspberry pis running raspian.

the build works fine on x64 ubuntu and it works fine when I run make from the command line on the raspberry pis.

But I have a build script to automate all the things that have to build and only in that case was it failing on the raspians.

the error I was getting was:

make[1]: Entering directory '/usr/src/linux-headers-4.19.75-v7+' Makefile:614: arch/armv7l/Makefile: No such file or directory make[1]:
*** No rule to make target 'arch/armv7l/Makefile'.  Stop. make[1]: Leaving directory '/usr/src/linux-headers-4.19.75-v7+'

Looked fine to me, and it worked fine from the command line just not my build script. See below for the solution.

Answer 1

I have a few raspberry pis that build different architectures so in my build script I had added

export ARCH= uname -m

and I'd append that to the end of the build result filename.

It turns out that something about the kernel module build where make forks make -C again uses the ARCH environment variable, which my script was changing unexpectedly.

I was confused by the message "*** No rule to make target 'arch/armv7l/Makefile'" because that looks legit, but apparently that was being derived from the incorrect ARCH environment variable.

I change the name of the ARCH variable in the script and it all started working again.

Hope this helps somebody.