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>2.3. Hello World (part 2)</H1
><P
>As of Linux 2.4, you can rename the init and cleanup functions of your modules; they no longer have to be called
<TT
CLASS="FUNCTION"
>init_module()</TT
> and <TT
CLASS="FUNCTION"
>cleanup_module()</TT
> respectively. This is done with the
<TT
CLASS="FUNCTION"
>module_init()</TT
> and <TT
CLASS="FUNCTION"
>module_exit()</TT
> macros. These macros are defined in <TT
CLASS="FILENAME"
>linux/init.h</TT
>. The only caveat is that your init and cleanup functions must be defined before calling
the macros, otherwise you'll get compilation errors. Here's an example of this technique:</P
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><B
>Example 2-3. hello-2.c</B
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>/* hello-2.c - Demonstrating the module_init() and module_exit() macros. This is the
* preferred over using init_module() and cleanup_module().
*/
#include <linux/module.h> // Needed by all modules
#include <linux/kernel.h> // Needed for KERN_ALERT
#include <linux/init.h> // Needed for the macros
static int hello_2_init(void)
{
printk(KERN_ALERT "Hello, world 2\n");
return 0;
}
static void hello_2_exit(void)
{
printk(KERN_ALERT "Goodbye, world 2\n");
}
module_init(hello_2_init);
module_exit(hello_2_exit);</PRE
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><P
>So now we have two real kernel modules under our belt. With productivity as high as ours, we should have a high powered
Makefile. Here's a more advanced Makefile which will compile both our modules at the same time. It's optimized for brevity
and scalability. If you don't understand it, I urge you to read the makefile info pages or the GNU Make Manual.</P
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><P
><B
>Example 2-4. Makefile for both our modules</B
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>WARN := -W -Wall -Wstrict-prototypes -Wmissing-prototypes
INCLUDE := -isystem /lib/modules/`uname -r`/build/include
CFLAGS := -O2 -DMODULE -D__KERNEL__ ${WARN} ${INCLUDE}
CC := gcc-3.0
OBJS := ${patsubst %.c, %.o, ${wildcard *.c}}
all: ${OBJS}
.PHONY: clean
clean:
rm -rf *.o</PRE
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><P
>As an exercise to the reader, if we had another module in the same directory, say <TT
CLASS="FILENAME"
>hello-3.c</TT
>, how
would you modify this Makefile to automatically compile that module?</P
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>Hello World (part 3): The <TT
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>__init</TT
> and <TT
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>__exit</TT
> Macros</TD
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