Re: Reg:current a pointer to task_struct

[george anzinger <george@mvista.com>]

"SATHISH.J" wrote:
> 
> Hi,
> 
> Please help me with the following:
> 
> I tried to go through get_current function which is in assembly.
> 
> static inline struct task_struct * get_current(void) {
>         struct task_struct *current;
>         __asm__("andl %%esp,%0; ":"=r" (current) : "0" (~8191UL));
>         return current;
>  }
> 
> Please tell me what is done here. Does current refer to process onproc.

Actually the code returns the stack pointer (esp) anded with ~8191
(FFFE000).

The trick is that kernel task structures are allocated at the low end of
the kernel stack for each task.  The stack is a the high end of the
address range and works down.  (Kernel stack overflow will "eat" the
task structure.)

current is (struct tast_struct *) and points to the task_struc for the
current task (how could it be otherwise, given that it comes from the
tasks stack pointer).

George