On Sat, 19 May 2007 04:55:12 -0700 kernel coder wrote:
> hi,
>
> I'm trying to implement a system call for x86_64. Mine processor is
> dual core opetron.There is very little material on web for
> implementing system calls for x86_64 processor for 2.6 series kernel.I
> tried to implement a new system call by observing the existing
> implementation but to no success.Following are files names and changes
> made.
Your example is very CPU-independent, i.e., not x86_64-specific,
so following examples of recently-added syscalls should be good enough.
I used your "patch" below (with a few small modifications) on
2.6.22-rc2 and it worked fine.
Linux unicorn 2.6.22-rc2 #2 SMP Sun May 20 22:22:36 PDT 2007 x86_64 x86_64 x86_64 GNU/Linux
...
[ 98.369454] new system call
> //////////////////////////////////////////////////
> file-> include/asm-x86_64/unistd.h
>
> #define __NR_newcall 273
> __SYSCALL(__NR_newcall, sys_newcall)
>
> #define __NR_syscall_max __NR_newcall
syscall_max is no longer used.
>
> //////////////////////////////////////////////////
> file-> include/linux/syscalls.h
>
> asmlinkage unsigned long sys_newcall(char __user *buf);
not unsigned.
>
> /////////////////////////////////////////////
> file--> fs/read_write.c
>
> asmlinkage unsigned long sys_newcall(char __user * buf){
not unsigned.
>
> printk("new system call \n");
> ret 0;
return 0;
> }
>
> EXPORT_SYMBOL_GPL(sys_write)
EXPORT_SYMBOL_GPL(sys_newcall);
> Please let me know where i'm doing wrong .Following is program which
> is calling mine system call
>
>
> #include <stdlib.h>
> #include <stdio.h>
> #include <sys/unistd.h>
#include <unistd.h>
> #include <sys/syscall.h>
>
> long int ret;
> int num = 243;
> char buffer=[20];
eh? does not compile.
>
> int main() {
>
>
> asm ("syscall;"
> : "=a" (ret)
> : "0" (num),
> "D" (buffer),
> );
I just used the syscall() glibc interface instead of asm:
ret = syscall(__NR_newcall);
> return ret;
> }
>
> When i call this ,nothing gets printed in file /var/log/messages.Am i
> missing something ?
Mostly typos...
> Actually i wana pass a pointer to kernel from user space.Later on data
> will be copied to that memory location .i am thinking of using
> copy_to_user for copying data.Buffer passed through system call will
> be used by kernel function as circular ring.And portions of this ring
> will get updated frequently even after system call has returned.
>
> Is there any better way to do this?
Sounds mostly OK to me.
Where are the ring head, tail, size, etc. maintained?
---
~Randy
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