mjhjmtu

I'm trying to compile a Linux kernel from source (https://github.com/UDOOboard/linux_kernel) on ubuntu virtualbox.

When I run:

ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- make modules

I get a bunch of warnings like:

WARNING: "do_sync_read" [fs/nfs/nfs.ko] has no CRC!

These modules aren't being built. How do I resolve this issue?

This thread looks related to your error message, titled: kbuild: bogus has no CRC warning:

# 2004/08/15 11:54:27+02:00 sam@xxxxxxxxxxxxxxxxx 
# kbuild: Bogus "has no CRC" in external module builds
# 
# From: Pavel Roskin <proski@xxxxxxx>
# The recent fixes for the external module build have fixed the major
# breakage, but they left one annoyance unfixed. If CONFIG_MODVERSIONS is
# disabled, a warning is printed for every exported symbol that is has no
# CRC. For instance, I see this when compiling the standalone Orinoco
# driver on Linux 2.6.6-rc3:
# 
# *** Warning: "__orinoco_down" [/usr/local/src/orinoco/spectrum_cs.ko] has
# no CRC!
# *** Warning: "hermes_struct_init" [/usr/local/src/orinoco/spectrum_cs.ko]
# has no CRC!
# *** Warning: "free_orinocodev" [/usr/local/src/orinoco/spectrum_cs.ko] has
# no CRC!
# [further warnings skipped]

From this thread if you search for "CONFIG_MODVERSIONS linux" you'll end up on this page titled: Kernel Symbols and CONFIG_MODVERSIONS. Excerpt from that page:

CONFIG_MODVERSIONS is a notion thought up to make people's lives
easier. In essence, what it is meant to achieve is that if you have a
module you can attempt to load that module into any kernel, safe in the
knowledge that it will fail to load if any of the kernel data
structures, types or functions that the module uses have changed.

If your kernel is not compiled with CONFIG_MODVERSIONS enabled you
will only be able to load modules that were compiled specifically for
that kernel version and that were also compiled without MODVERSIONS
enabled.

However, if your kernel is compiled with CONFIG_MODVERSIONS enabled
you will be able to load a module that was compiled for the same
kernel version with MODVERSIONS turned off. But - here's the important
part folks - you will also be able to load any modules compiled with
MDOVERSIONS turned on, as long as the kernel API that the module uses
hasn't changed.

Within that page is this:

If you only require that none of the module's symbols are exported
you can use the EXPORT_NO_SYMBOLS macro.

I'd build with this set, since I don't think you're planning to take the compiled modules from this system to any other.

NOTE: You can do this in either the .config file or during make menuconfig.

References

• https://www.linux.com/forums/kernel-development/module-versions