From: kernelnewbies-bounces@xxxxxxxxxxxxxxxxx [mailto:kernelnewbies-bounces@xxxxxxxxxxxxxxxxx]
On Behalf Of ??
Sent: Monday, June 18, 2012 6:40 PM
To: kernelnewbies
Subject: A confusion about invoking my syscall
Hello everyone:
I append a simple syscall in kernel. and the function is as follows:
asmlinkage long sys_mysyscall(long data)
{
printk("This is my syscall!\n");
return data;
}
and i test it sucessfully in user space . and the test program:
#include <linux/unistd.h>
#include <syscall.h>
#include <sys/types.h>
#include <stdio.h>
int main(void)
{
long n = 0,m = 0,pid1,pid2;
n = syscall(345,190);// #define __NR_mysyscall 345
printf("n = %ld\n",n);
pid1 = syscall(SYS_getpid); //getpid
printf("pid = %ld\n",pid1);
pid2 = syscall(20); //getpid
printf("pid = %ld\n",pid2);
return 0;
}
and the result:
n = 190
pid = 4097
pid = 4097
but if the test program is:
#include <linux/unistd.h>
#include <syscall.h>
#include <sys/types.h>
#include <stdio.h>
int main(void)
{
long n = 0,m = 0,pid1,pid2;
n = syscall(345,190);// #define __NR_mysyscall 345
printf("n = %ld\n",n);
m = syscall(SYS_mysyscall,190);
printf("m = %ld\n",m);
pid1 = syscall(SYS_getpid); //getpid
printf("pid = %ld\n",pid1);
pid2 = syscall(20); //getpid
printf("pid = %ld\n",pid2);
return 0;
}
and the result:
wanny@wanny-C-Notebook-XXXX:~/syscall/src$ gcc test1.c
test1.c: In function ‘main’:
test1.c:13:14: error: ‘SYS_mysyscall’ undeclared (first use in this function)
test1.c:13:14: note: each undeclared identifier is reported only once for each function it appears in
why i can't invoke my syscall with "SYS_mysyscall"?
Thanks in advance!
Because it appears you never defined the symbol SYS_mysyscall.
Jeff Haran
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