Makefile to linux kernel module with multiple source files

Question

I'm learning Linux Kernel programming. I'm trying to build my module from multiple files. It builds and loads, but there is no messages in dmesg. What is going wrong?

solution.c:

#include <linux/init.h>
#include <linux/module.h>
#include "checker.h"

static const char* msg = "Hello from my module!";
extern void call_me(const char*);

static int __init init(void)
{
    printk(KERN_INFO "322\n");
    call_me(msg);
    printk(KERN_ALERT "After the function\n");
    return 0;
}

 static void __exit exitFromModule(void)
{
    printk(KERN_ALERT "BYE\n");
    return;
}

module_init(init);
module_exit(exitFromModule);

checker.h:

#include <linux/module.h>
 void call_me(const char* str);

checker.c:

#include "checker.h" #include <linux/kernel.h>

void call_me(const char* str)
{
    printk("<1>FROM CALL_ME!\n");
    return;
}

Makefile:

CURRENT = $(shell uname -r)
KDIR = /lib/modules/$(CURRENT)/build
PWD = $(shell pwd)
DEST = /lib/modules/$(CURRENT)/misc
TARGET = solution

obj-m := $(TARGET).o
solution-objs  :=  checker.o

all:
        make -C $(KDIR) M=$(PWD)  modules

clean:
        make -C $(KDIR) M=$(PWD) clean
        @rm -f *.o .*.cmd .*.flags *.mod.c *.order;
        @rm -f .*.*.cmd *.symvers *~ *.*~ TODO.*
        @rm -fR .tmp*
        @rm -rf .tmp_versions

After that i start make and it compiles. But after insmod there is messages in dmesg.

Are you getting anything in dmesg? The prints from the `init` functions? Can you attach the dmesg from before and after loading the module? — Ajay Brahmakshatriya, Jul 02 '21 at 19:15
@AjayBrahmakshatriya. sorry, i'm newbie and i'm unable to post images. There is my output. I've cleaned dmesg and it is empty after module inserting. alex@alex-Lenovo-ideapad-100-15IBD:~/l2$ sudo dmesg -c alex@alex-Lenovo-ideapad-100-15IBD:~/l2$ sudo insmod solution.ko alex@alex-Lenovo-ideapad-100-15IBD:~/l2$ sudo dmesg alex@alex-Lenovo-ideapad-100-15IBD:~/l2$ — WelcomeToMyTutorial, Jul 02 '21 at 19:32
The line `solution-objs := checker.o` means that your module is compiled only from the ``checker.c`` file. You need to add **all** source (objects) files into `xxx-objs` list. But you cannot add object with the same name as the module itself, for that you need either to rename a module or a source file. See [that question](https://stackoverflow.com/questions/13606075/building-a-kernel-module-from-several-source-files-which-one-of-them-has-the-sam) for more info. — Tsyvarev, Jul 02 '21 at 20:29
Does this answer your question? [Building a kernel module from several source files which one of them has the same name as the module](https://stackoverflow.com/questions/13606075/building-a-kernel-module-from-several-source-files-which-one-of-them-has-the-sam) — Tsyvarev, Jul 02 '21 at 20:32
@Tsyvarev, well, it builds but i have an error: insmod: ERROR: could not insert module module.ko: Invalid parameters. What can be wrong? — WelcomeToMyTutorial, Jul 02 '21 at 22:08
Probably, `dmesg` contains additional information about this error. — Tsyvarev, Jul 03 '21 at 07:05

Makefile to linux kernel module with multiple source files

0 Answers0