Tengo problemas para que los módulos del núcleo se construyan en mi máquina. Cada vez que construyo un módulo, modpost siempre dice que hay cero módulos:

MODPOST 0 modules

Para solucionar el problema, escribí un módulo de prueba (hello.c):

#include <linux/module.h>       /* Needed by all modules */
#include <linux/kernel.h>       /* Needed for KERN_INFO */
#include <linux/init.h>         /* Needed for the macros */

static int __init hello_start(void)
{
printk(KERN_INFO "Loading hello module...\n");
printk(KERN_INFO "Hello world\n");
return 0;
}

static void __exit hello_end(void)
{
printk(KERN_INFO "Goodbye Mr.\n");
}

module_init(hello_start);
module_exit(hello_end);

Aquí está el Makefile para el módulo:

obj-m = hello.o
KVERSION = $(shell uname -r)
all:
        make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) modules
clean:
        make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) clean

Cuando lo construyo en mi máquina, obtengo el siguiente resultado:

make -C /lib/modules/2.6.32-27-generic/build M=/home/waffleman/tmp/mod-test modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.32-27-generic'
  CC [M]  /home/waffleman/tmp/mod-test/hello.o
  Building modules, stage 2.
  MODPOST 0 modules
make[1]: Leaving directory `/usr/src/linux-headers-2.6.32-27-generic'

Cuando hago el módulo en otra máquina, tiene éxito:

make -C /lib/modules/2.6.24-27-generic/build M=/home/somedude/tmp/mod-test modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.24-27-generic'
  CC [M]  /home/somedude/tmp/mod-test/hello.o
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /home/somedude/tmp/mod-test/hello.mod.o
  LD [M]  /home/somedude/tmp/mod-test/hello.ko
make[1]: Leaving directory `/usr/src/linux-headers-2.6.24-27-generic'

Busqué cualquier documentación relevante sobre modpost, pero encontré poco. ¿Alguien sabe cómo modpost decide qué construir? ¿Hay un entorno que posiblemente me estoy perdiendo?

Por cierto, esto es lo que estoy ejecutando:

uname -a
Linux waffleman-desktop 2.6.32-27-generic #49-Ubuntu SMP Wed Dec 1 23:52:12 UTC 2010 i686 GNU/Linux

Editar

Aquí está make run con V = 1:

make -C /lib/modules/2.6.32-27-generic/build M=/home/waffleman/tmp/mod-test modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.32-27-generic'
test -e include/linux/autoconf.h -a -e include/config/auto.conf || (        \
    echo;                               \
    echo "  ERROR: Kernel configuration is invalid.";       \
    echo "         include/linux/autoconf.h or include/config/auto.conf are missing.";  \
    echo "         Run 'make oldconfig && make prepare' on kernel src to fix it.";  \
    echo;                               \
    /bin/false)
mkdir -p /home/waffleman/tmp/mod-test/.tmp_versions ; rm -f /home/waffleman/tmp/mod-test/.tmp_versions/*
make -f scripts/Makefile.build obj=/home/waffleman/tmp/mod-test
  gcc -Wp,-MD,/home/waffleman/tmp/mod-test/.hello.o.d  -nostdinc -isystem /usr/lib/gcc/i486-linux-gnu/4.4.3/include  -Iinclude  -I/usr/src/linux-headers-2.6.32-27-generic/arch/x86/include -include include/linux/autoconf.h -Iubuntu/include  -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -fno-delete-null-pointer-checks -O2 -m32 -msoft-float -mregparm=3 -freg-struct-return -mpreferred-stack-boundary=2 -march=i586 -mtune=generic -maccumulate-outgoing-args -Wa,-mtune=generic32 -ffreestanding -fstack-protector -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -Wframe-larger-than=1024 -fno-omit-frame-pointer -fno-optimize-sibling-calls -pg -Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow -fno-dwarf2-cfi-asm -fconserve-stack  -DMODULE -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(hello)"  -D"KBUILD_MODNAME=KBUILD_STR(hello)"  -c -o /home/waffleman/tmp/mod-test/.tmp_hello.o /home/waffleman/tmp/mod-test/hello.c
  set -e ; perl /usr/src/linux-headers-2.6.32-27-generic/scripts/recordmcount.pl "i386" "32" "objdump" "objcopy" "gcc" "ld" "nm" "" "" "1" "/home/waffleman/tmp/mod-test/hello.o";
(cat /dev/null;   echo kernel//home/waffleman/tmp/mod-test/hello.ko;) > /home/waffleman/tmp/mod-test/modules.order
make -f /usr/src/linux-headers-2.6.32-27-generic/scripts/Makefile.modpost
  scripts/mod/modpost -m -a -i /usr/src/linux-headers-2.6.32-27-generic/Module.symvers -I /home/waffleman/tmp/mod-test/Module.symvers  -o /home/waffleman/tmp/mod-test/Module.symvers -S -w  -s
make[1]: Leaving directory `/usr/src/linux-headers-2.6.32-27-generic'
waffleman@waffleman-desktop:~/tmp/mod-test$ cat /home/waffleman/tmp/mod-test/modules.order
kernel//home/waffleman/tmp/mod-test/hello.ko