Linux: modpost does not build anything

Question

I am having problems getting any kernel modules to build on my machine. Whenever I build a module, modpost always says there are zero modules:

MODPOST 0 modu         


        

Answer 1

I solved this problem by correcting Makefile, i.e.:

obj-m := modulename.o

Answer 2

I spent all day glued to my computer fighting this precise problem..which ended up mysteriously disappearing like for OP.

I can at least offer this meager detail from my experience: I was getting the same output as OP (for make V=1) and putting print statements in ${kernel_directory}/scripts/makefile.build showed that obj-m was strangely NOT being set after including my makefile, even though it was clearly typed as above.

I did a bunch of fooling around with the line "obj-m += hello.o" and the ones around it. Eventually it magically worked..although it looked exactly the same as before in the end. Maybe I had copied those lines from a tutorial online and it contained some sort of invalid/incorrect character?

For anyone experiencing this, verify that obj-m is in fact getting set to hello.o
If it mysteriously isn't, delete the line, hell the whole Makefile, and retype it.

I know that's not much help; I wish I could reproduce what happened!

Answer 3

I guess you copied the contents of the Makefile from a PDF or some HTML document. The hyphens used are somewhat weird. Just try replacing the hyphens in the makefile; it will work like a charm.

Answer 4

I had the same problem. Finally, I rebuilt the kernel, rewrote the makefile. It worked finally.

I guess the main reason is because I had M=$(PWD) modules in the following line right after make ARCH=arm...

Answer 5

I can only guess your kernel build environment is botched, because it passes both the theoretical check (the look of the developer) as well as the practical test:

make -C /lib/modules/2.6.36-rc8-32-desktop/build M=/dev/shm modules
make[1]: Entering directory `/usr/src/linux-2.6.36-rc8-32-obj/x86_64/desktop'
make -C ../../../linux-2.6.36-rc8-32 O=/usr/src/linux-2.6.36-rc8-32-obj/x86_64/desktop/. modules
  CC [M]  /dev/shm/hello.o
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /dev/shm/hello.mod.o
  LD [M]  /dev/shm/hello.ko
make[1]: Leaving directory `/usr/src/linux-2.6.36-rc8-32-obj/x86_64/desktop'

Answer 6

I was able to solve this problem by putting the

obj-m += <module name>.o

In a separate file named Kbuild. See Linux/documentation/kbuild/modules.txt for a hint as to why this might work