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leetow2006

Member

Registered: 2013-02-13

Posts: 21

How to correct the error "implicit declaration of function '

Look:

//the file:Makefile
ifneq ($(KERNELRELEASE),)
obj-m += __module_address.o
else
PWD := $(shell pwd)
KVER := $(shell uname -r)
KDIR := /lib/modules/$(KVER)/build
all:
	$(MAKE) -C $(KDIR) M=$(PWD)
clean:
	rm -rf *.o *.mod.c *.ko *.symvers *.order *.markers *~
endif

//the file __module_address.c
#include <linux/module.h>
#include <linux/init.h>
MODULE_LICENSE("GPL"); 
static int __init __module_address_init(void); 
static void __exit __module_address_exit(void);

int a_module(void)
{
	return 0;
}
int __init __module_address_init(void) 
{ 
	struct module * ret ; 
	unsigned long addr = (unsigned long)a_module; 

	preempt_disable();   
	ret = __module_address(addr) ;
	preempt_enable();   

	if( ret != NULL )
	{
		printk("<0>ret->name: %s\n",ret->name);   
		printk("<0>ret->state: %d\n",ret->state);   
       	        printk("<0>ret->core_size: %lu\n",ret->core_size);  
                printk("<0>refs of %s is %d\n",ret->name, module_refcount(ret)); 
	}	
	else
	{
		printk("<0>__module_address return NULL !\n");
	}	

	return 0; 
}

void __exit __module_address_exit(void) 
{ 
	printk("<0>module exit ok!\n"); 
}

module_init(__module_address_init); 
module_exit(__module_address_exit); 

When I compile the file __module_address.c,it always display
the error: "implicit declaration of function '__module_address'",
how to correct it?

ilsensine

Member

Registered: 2013-03-26

Posts: 32

Re: How to correct the error "implicit declaration of function '

I don't get this warning (I get two format warning on the printks, but it's an unrelated issue). Tested on 3.11.2. The __module_address function is correctly defined in module.h.

btw I think your use of preempt_disable/enable is incorrect: first of all, for _this_ particular use, I think you can avoid disabling preemption at all, because the module can't disappear while executing its own code (if it happens, it's a serious bug). It doesn't hurt, anyway. If/when you'll use __module_addres for obtaining the information on *another* module, then you must extend the preempt-disabled region until you've done with the returned struct.

Last edited by ilsensine (2013-09-27 07:09:55)