Hello everyone,
I am new to this forum. Recently I am learning how to link static libraries to kernel module.
I have found simliar posts in : http://www.linuxquestions.org/questi...module-587406/

I have a test.c file with the following contents :

int TEST ( int p1 , int p2 )
{
return p1 + p2 ;
}

I compiled it with :

gcc -o test.o -c test.c

I made the static library with :

ar -rcs test.a test.o

I tried to use the TEST function in a kernel module, however, I found out that the passed in values of the parameters are totally wrong, and made the function give wrong result. Does any one know if there is special ways or flags should be added when making the static library for kernel module? Thank you in advanced for your advise !

John Sung

The kernel module file looks like below :
//=================================================================
// module.c
//=================================================================
#include <linux/module.h>
int TEST ( int , int ) ;
static int __init Module_Init ( void )
{
printk ( "TEST result %d\n" , TEST( 1 , 2 ) ) ;
return 0 ;
}
static void __exit Module_Exit ( void )
{
return ;
}
module_init ( Module_Init ) ;
module_exit ( Module_Exit ) ;
MODULE_AUTHOR ( "test <test@test.com>" ) ;
MODULE_DESCRIPTION ( "This is a Test Module" ) ;
MODULE_LICENSE ( "GPL" ) ;

//=================================================================
// Makefile
//=================================================================

ifndef KERNELDIR
KERNELDIR := /lib/modules/$(shell uname -r)/build
endif

obj-m := TestMod.o
TestMod-objs := module.o test.a

all:
$(MAKE) -C $(KERNELDIR) M=$(PWD)

clean:
$(MAKE) -C $(KERNELDIR) M=$(PWD) clean

install:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install
/sbin/depmod -ae

Usually, you should be building the kernel and your module in the same source tree at the same time with the same version of gcc. In any case, to build a kernel module you need to give the same options to gcc as were used when the kernel was built. For example, if your kernel is 64-bit, you need -m64. See the file Documentation/kbuild/modules.txt in the kernel source tree.

1 members found this post helpful.

I met the same issue.

printk ( "TEST result %d\n" , TEST( 1 , 2 ) ) ;

->report

[ 985.040060] overflow in relocation type 10 val ffffffffa0499024
[ 985.040063] `drv' likely not compiled with -mcmodel=kernel


so ,add -mcmodel=kernel when compiling, the issue has been solved.