Darling: LKM: incorrect vermagic

[lmuthu]

I am trying to build darling on Ubuntu16.04 but the build fails with the following error:

[ 95%] Building CXX object src/external/JavaScriptCore/CMakeFiles/JavaScriptCore.dir/runtime/CommonIdentifiers.o
clang: error: unable to execute command: Killed
clang: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
Target: x86_64-apple-darwin11
Thread model: posix
InstalledDir: /usr/bin
clang: note: diagnostic msg: PLEASE submit a bug report to http://llvm.org/bugs/ and include the crash backtrace, preprocessed source, and associated run script.
clang: note: diagnostic msg: Error generating preprocessed source(s) - cannot generate preprocessed source with multiple -arch options.
src/external/JavaScriptCore/CMakeFiles/JavaScriptCore.dir/build.make:4598: recipe for target 'src/external/JavaScriptCore/CMakeFiles/JavaScriptCore.dir/runtime/CommonIdentifiers.o' failed
make[2]: *** [src/external/JavaScriptCore/CMakeFiles/JavaScriptCore.dir/runtime/CommonIdentifiers.o] Error 254
CMakeFiles/Makefile2:51126: recipe for target 'src/external/JavaScriptCore/CMakeFiles/JavaScriptCore.dir/all' failed
make[1]: *** [src/external/JavaScriptCore/CMakeFiles/JavaScriptCore.dir/all] Error 2
Makefile:127: recipe for target 'all' failed


root@UbuntuSixteen:~/darling/build/src/external# uname -r
4.13.0-39-generic

root@UbuntuSixteen:~/darling/build/src/external# clang --version
clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

Please help resolve this.

[stek29]

How much ram do you have?

[lmuthu]

Its a VM on a ESX host. It has 1GB RAM.

[bugaevc]

That sure looks like one of your compiler processes was OOM-killed. Try just running make again; if that doesn't help make sure you're not running too much compiler processes in parallel (as would be the case with e.g. make -j8), or increase RAM (and/or swap) size.

[lmuthu]

Hi , After increasing the RAM to 4GB, I was able to compile and install. But when i run "darling shell", I get the following error:

root@UbuntuSixteen:/lib/modules# darling shell
modprobe: ERROR: could not insert 'darling_mach': Exec format error
Failed to load the kernel module

Dmesg has the following logs:
[14586.647297] darling_mach: version magic '4.13.0-38-generic SMP mod_unload ' should be '4.13.0-39-generic SMP mod_unload '

root@UbuntuSixteen:/lib/modules# uname -r
4.13.0-39-generic

Please help.

Regards,
Muthu

[bugaevc]

This looks like the kernel module was built for a different version of the kernel that you are trying to use it with.

If you have recently updated your kernel, try rebooting to the new one first.

[lmuthu]

The kernel was upgraded from 4.10.0.28 to 4.10.0.39. But I started the build process after the kernel upgrade.

[stek29]

@lmuthu please try to re-build and re-install lkm

[bugaevc]

I can reproduce this:

$ modinfo /usr/lib/modules/4.16.7-300.fc28.x86_64/extra/darling-mach.ko
filename:       /usr/lib/modules/4.16.7-300.fc28.x86_64/extra/darling-mach.ko
license:        GPL
depends:        
retpoline:      Y
name:           darling_mach
vermagic:       4.16.7-200.fc27.x86_64 SMP mod_unload 

I have both 4.16.7-300.fc28 and 4.16.7-200.fc27 installed, it seems the kernel build system gets confused somewhere over them both being 4.16.7. uname -r, as used by src/lkm/Makefile, correctly reports 4.16.7-300.fc28.x86_64.

After a dnf remove kernel-4.16.7-200.fc27, the issue went away.

[ahyattdev]

I resolved this on Ubuntu with the following (all paths relative to the Darling source root unless otherwise noted):

1. apt autoremove
2. find src/lkm -name \*.o -delete
3. rm src/lkm/darling-mach.ko
4. rm -rf src/lkm (In build root, very important this time)
5. make lkm (In build root)
6. make lkm_install (In build root)

[ahyattdev]

@bugaevc @lmuthu @stek29 I am getting this issue on Ubuntu 18.10. Our kernel module build system appears to build for the older kernel while installing to the folder for the newer kernel.

[ahyattdev]

I have narrowed down the issue to the kernel build system not rebuilding darling-mach.mod.o, which is built once and never rebuilt when the kernel version changes. It contains the vermagic. I am going to implement a workaround.