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>2.7. Modules Spanning Multiple Files</H1
><P
>Sometimes it makes sense to divide a kernel module between several source files. In this case, you need to:</P
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><LI
><P
>In all the source files but one, add the line <B
CLASS="COMMAND"
>#define __NO_VERSION__</B
>. This is important
because <TT
CLASS="FILENAME"
>module.h</TT
> normally includes the definition of
<TT
CLASS="VARNAME"
>kernel_version</TT
>, a global variable with the kernel version the module is compiled for. If you need
<TT
CLASS="FILENAME"
>version.h</TT
>, you need to include it yourself, because <TT
CLASS="FILENAME"
>module.h</TT
> won't do it for you with <TT
CLASS="VARNAME"
>__NO_VERSION__</TT
>.</P
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><P
>Compile all the source files as usual.</P
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><P
>Combine all the object files into a single one. Under x86, use <B
CLASS="COMMAND"
>ld -m elf_i386 -r -o <module
name.o> <1st src file.o> <2nd src file.o></B
>.</P
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><P
>Here's an example of such a kernel module.</P
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><P
><B
>Example 2-8. start.c</B
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><PRE
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>/* start.c - Illustration of multi filed modules
*/
#include <linux/kernel.h> /* We're doing kernel work */
#include <linux/module.h> /* Specifically, a module */
int init_module(void)
{
printk("Hello, world - this is the kernel speaking\n");
return 0;
}</PRE
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><P
>The next file:</P
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><P
><B
>Example 2-9. stop.c</B
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><PRE
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>/* stop.c - Illustration of multi filed modules
*/
#if defined(CONFIG_MODVERSIONS) && ! defined(MODVERSIONS)
#include <linux/modversions.h> /* Will be explained later */
#define MODVERSIONS
#endif
#include <linux/kernel.h> /* We're doing kernel work */
#include <linux/module.h> /* Specifically, a module */
#define __NO_VERSION__ /* It's not THE file of the kernel module */
#include <linux/version.h> /* Not included by module.h because of
__NO_VERSION__ */
void cleanup_module()
{
printk("<1>Short is the life of a kernel module\n");
} </PRE
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><P
>And finally, the makefile:</P
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><A
NAME="AEN432"
></A
><P
><B
>Example 2-10. Makefile for a multi-filed module</B
></P
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>CC=gcc
MODCFLAGS := -O -Wall -DMODULE -D__KERNEL__
hello.o: hello2_start.o hello2_stop.o
ld -m elf_i386 -r -o hello2.o hello2_start.o hello2_stop.o
start.o: hello2_start.c
${CC} ${MODCFLAGS} -c hello2_start.c
stop.o: hello2_stop.c
${CC} ${MODCFLAGS} -c hello2_stop.c</PRE
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