Dear All,
I have written a small sample code for testing the EXPORT_SYMBOL macro
which exports the symbols to the global kernel symbol table. The sample
code is working fine in 2.6.9-1.667 kernel version, however it does not
works fine in 2.6.28 kernel version. I am getting the following errors
in 2.6.28 kernel version only.
insmod: error inserting 'import_func.ko': -1 Unknown symbol in module
When I see the /var/log/messages through dmesg command, I got the
following.
import_func: no symbol version for myexportfun
import_func: Unknown symbol myexportfun
The procedure I used for testing is as follows.
1) Insert the export_func module as
insmod export_func.ko
2) Check whether the symbols are exported or not
cat /proc/kallsyms | grep myexp
3) The function was exported fine and able to see the names in the
global kernel symbol table.
4) Now, insert the import_func module as
insmod import_func.ko
Then I got the above errors. But the same code is working fine in
2.6.9-1.667 kernel version without any errors. Please some one correct
me what am I doing wrong.
Thanks in advance.
With Regards,
Srinivas G
The following C file code exports the symbols to the kernel symbol
table.
-------------------------------------------------------------
#include <linux/init.h> /* for explicit init & exit */
#include <linux/kernel.h> /* for printk */
#include <linux/module.h> /* for MODULE_ definitions */
#include "expfunc.h"
MODULE_AUTHOR("Srinivas G");
MODULE_LICENSE("GPL");
void myexportfun(void) {
printk("<%s> I am a exported function - NEW!\n",__FUNCTION__); }
EXPORT_SYMBOL(myexportfun);
static int exp_init(void) {
printk("<%s> Module to demo export of symbols!\n",__FUNCTION__);
return 0;
}
static void exp_cleanup(void) {
printk("<%s> exiting symbol export demo module!\n",__FUNCTION__);
}
module_init(exp_init);
module_exit(exp_cleanup);
---------------------------------------------------------------
The header file contents are as follows.
#ifndef __EXPFUNC_H
#define __EXPFUNC_H
//extern void myexportfun(void);
void myexportfun(void);
#endif
----------------------------------------------------------------
The Makefile contents are as follows.
#
# Makefile to export a function name into the kernel symbol table #
Author: Srinivas G.
#
KDIR:=/lib/modules/$(shell uname -r)/build TRGT:=export_func
OBJS:=expfunc.o
EXTRA_CFLAGS +=-DEXPORT_SYMTAB -Wno-unused-variable -Wno-implicit
obj-m += $(TRGT).o
$(TRGT)-objs := $(OBJS)
default:
$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
clean:
$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) clean
---------------------------------------------------------------
The contents of the import module as follows.
#include <linux/init.h> /* for explicit init & exit */
#include <linux/kernel.h> /* for printk */
#include <linux/module.h> /* for MODULE_ definitions */
#include "../export/expfunc.h"
MODULE_AUTHOR("Srinivas G");
MODULE_LICENSE("GPL");
static int my_init(void) {
int i;
printk("<%s> Module to demo export of symbols\n",__FUNCTION__);
myexportfun();
return 0;
}
static void my_cleanup(void) {
printk("<%s> exiting symbol export demo module \n",__FUNCTION__);
}
module_init(my_init);
module_exit(my_cleanup);
----------------------------------------------------------------
The contents of the makefile as follows.
#
# Makefile for the demo of the import module program # Author: Srinivas
G.
#
KDIR:=/lib/modules/$(shell uname -r)/build TRGT:=import_func
OBJS:=impfunc.o
EXTRA_CFLAGS +=-DEXPORT_SYMTAB -Wno-unused-variable -Wno-implicit
obj-m += $(TRGT).o
$(TRGT)-objs := $(OBJS)
default:
$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
clean:
$(RM) *.ko *.o *.mod.* .*.cmd -r .tmp*
----------------------------------------------------------------
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