Retrieving session Id in linux kernel (Kernel Space)

问题

I want to retrieve the sessionid of the current process in linux kernel (Kernel Space). I saw task_struct has a field sessionid but it is defined only when the macro CONFIG_AUDITSYSCALL is ON. So i tried to build the kernel with this macro ON but still i was not getting the result. Also I tried getting its value from function with CONFIG_AUDITSYSCALL on audit_get_sessionid(current) but was getting either -1 or junk value ( different from getsid(0) method in user space).

I am struck at this point. Any suggestion would be of great help.

回答1:

You can take a look at the getsid syscall at here: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=kernel/sys.c#l1106

SYSCALL_DEFINE1(getsid, pid_t, pid)
{
     struct task_struct *p;
     struct pid *sid;
     int retval;

     rcu_read_lock();
     if (!pid)
             sid = task_session(current);
     else {
     ...

Which suggest you can use the kernel function task_session() to get the session id.