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Ciro Santilli
2018-02-13 16:09:16 +00:00
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31
run-on-host.adoc
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@@ -1,26 +1,14 @@
[[run-on-host]]
= Run on host
=== Run on host
This method runs the kernel modules directly on your host computer
without a VM, and saves you the compilation time and disk usage of the
virtual machine method.
This method runs the kernel modules directly on your host computer without a VM, and saves you the compilation time and disk usage of the virtual machine method.
It has however severe limitations, and you will soon see that the
compilation time and disk usage are well worth it:
It has however severe limitations, and you will soon see that the compilation time and disk usage are well worth it:
* can't control which kernel version and build options to use. So some
of the modules will likely not compile because of kernel API changes,
since
https://stackoverflow.com/questions/37098482/how-to-build-a-linux-kernel-module-so-that-it-is-compatible-with-all-kernel-rele/45429681#45429681[the
Linux kernel does not have a stable kernel module API].
* can't control which kernel version and build options to use. So some of the modules will likely not compile because of kernel API changes, since https://stackoverflow.com/questions/37098482/how-to-build-a-linux-kernel-module-so-that-it-is-compatible-with-all-kernel-rele/45429681#45429681[the Linux kernel does not have a stable kernel module API].
* bugs can easily break you system. E.g.:
** segfaults can trivially lead to a kernel crash, and require a reboot
** your disk could get erased. Yes, this can also happen with `sudo`
from userland. But you should not use `sudo` when developing newbie
programs. And for the kernel you don't have the choice not to use `sudo`
** even more subtle system corruption such as
https://unix.stackexchange.com/questions/78858/cannot-remove-or-reinsert-kernel-module-after-error-while-inserting-it-without-r[not
being able to rmmod]
** your disk could get erased. Yes, this can also happen with `sudo` from userland. But you should not use `sudo` when developing newbie programs. And for the kernel you don't have the choice not to use `sudo`
** even more subtle system corruption such as https://unix.stackexchange.com/questions/78858/cannot-remove-or-reinsert-kernel-module-after-error-while-inserting-it-without-r[not being able to rmmod]
* can't control which hardware is used, notably the CPU architecture
* can't step debug it with GDB easily
@@ -31,17 +19,14 @@ cd kernel_module
./make-host.sh
....
If the compilation of any of the C files fails because of kernel or
toolchain differences that we don't control on the host, just rename it
to remove the `.c` extension and try again:
If the compilation of any of the C files fails because of kernel or toolchain differences that we don't control on the host, just rename it to remove the `.c` extension and try again:
....
mv broken.c broken.c~
./build_host
....
Once you manage to compile, and have come to terms with the fact that
this may blow up your host, try it out with:
Once you manage to compile, and have come to terms with the fact that this may blow up your host, try it out with:
....
sudo insmod hello.ko