"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
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