hi,
Any one plz help me....
I want to write a system call into a kernel.
i followed all steps of writing a system call to kernel.
i did.....
1) updated ./linux/include/asm/unistd.h
2)updated ./linux/arch/386/kernel/syscall_table.S
3) then wrote my own system call code in ./linux/kernel/sys.c file
asmlinkage long sys_getjiffies( void )
{
return (long)get_jiffies_64(); // read jiffies with the
}
return (long)get_jiffies_64(); // read jiffies with the
get_jiffies_64 function.}
//The Linux kernel maintains a global variable called
jiffies, which represents the number of timer ticks since the machine started 4) after compiling kernel , when i tried to call that system call , it returned me -1.
Following code i used to call system call created above.
#include <linux/unistd.h>
#include <sys/syscall.h>
#define __NR_getjiffies 320
int main()
{
long jiffies;
jiffies = syscall( __NR_getjiffies );
printf( "Current jiffies is %lx\n", jiffies );
return 0;
}
#include <sys/syscall.h>
#define __NR_getjiffies 320
int main()
{
long jiffies;
jiffies = syscall( __NR_getjiffies );
printf( "Current jiffies is %lx\n", jiffies );
return 0;
}
Plz help me....... why system call is returning negative value.
Thanks in advance.
