Thank you very much,I hope now it will work. On 6/5/05, Kirk True <kernel@xxxxxxxxxxxxxxxxx> wrote:> Hi,> > > I tried to implement a new system call. I used the instructions of> > http://user-mode-linux.sourceforge.net/lksct/index.html> > > The coak() is supposed to print a message, we could see it using> > dmesg. But, it doesnt happen.> > I don't know about UML, but here's a little document I wrote up for> myself (I'm so forgetful). Perhaps it will work for you :)> > -------------> > Adding a system call is easy. Just follow the following steps:> > 1. Create the new system call> 1. If the system call is in a new file, add it to the> appropriate Makefile> 2. Add the system call to arch/i386/kernel/syscall_table.S> 3. Add a #define to include/asm-i386/unistd.h> 4. Create a user-space application that calls the system call> > Let's take these one by one…> > 1. Create the new system call> > The first order of business is to define the system call itself. I'm not> sure if there's a particular function signature format to follow or not.> It does seem, however, that most – if not all – system calls include a> prefix of "sys_" though this may just be a naming convention.> > Here's an example:> > asmlinkage int sys_helloworld(void);> > Note that the source file in which the system call is included must> #include linux/linkage.h (for "asmlinkage").> > 1.1. If the system call is in a new file, add it to the appropriate> Makefile> > If we added our new system call to a new file, naturally that file must> be compiled into the kernel image. Therefore it should be added into the> Makefile in the directory. If you forget this step you may get no-ops> with your user-space program.> > 2. Add the system call to arch/i386/kernel/syscall_table.S> > This one's really easy: just add a line with the format to the end of> the file:> > .long <function_name>> > Example:> > .long sys_helloworld> > That's it!> > 3. Add a #define to include/asm-i386/unistd.h> > Find the last #define __NR_<system_call_function> and add the new system> call incrementing the number. Also, the NR_syscalls value should be> incremented too.> > For instance:> > #define __NR_keyctl 288> > #define NR_syscalls 289> > Would become:> > #define __NR_keyctl 288> #define __NR_helloworld 289> > #define NR_syscalls 290> > 4. Create a user-space application that calls the system call> > To benefit from the system call, you have to invoke it in a user-space> application. For custom system calls, since there is no nice C library> wrapper, we have to perform an archaic trick. The _syscallN macro will> expand into a declaration of our new system call.> > For instance, to call our helloworld system call as defined above, we'd> need to declare the function signature thusly:> > _syscall0(int, helloworld);> > The number after _syscall is the number of parameters. I'm assuming the> first parameter to the macro is the return type. The name provided as> the second argument is then prepended with the string "__NR_" and looked> for in include/asm-i386/unistd.h.> > The function can then be invoked thusly:> > int main(void) {> return helloworld();> }> > Note: compiling the user-space application when running on a kernel that> doesn't have the system call will fail to find the entry in include/asm-> i386/unistd.h. You have to instead tell gcc where to find the> appropriate include file instead. For me that was done thusly:> > gcc --include=/usr/src/<your linux kernel>/include/asm-i386/unistd.h <src.c>> > -------------> > Hope this helps...> > Kirk> > -- Karane.ÿòž®w¥?ì‰ëÿ éiy§!¢Ø^®Wš®v›¢ëm…ââžìdz¹Þ—ð+r¯{øm¶Ÿÿþf¢—ùåþX§» è®äz¹Þ–w°n'¬üPþm§ÿÿ‘êçzYÞÁ¸ž³ú+ƒ÷Ú
