Hi list, I would like to know how the thread_info address is calculated? As per the LKD book: struct thread_info is stored on the kernel stack. On x86, current is calculated by masking out the 13 least-significant bits of the stack pointer to obtain the thread_info structure.This is done by the current_thread_info() function.The assembly is shown here: movl $-8192, %eax andl %esp, %eax This assumes that the stack size is 8KB. But in code i found that: /* how to get the thread information struct from C */ static inline struct thread_info *current_thread_info(void) { return (struct thread_info *) (current_stack_pointer & ~(THREAD_SIZE - 1)); } /* how to get the current stack pointer from C */ static inline unsigned long current_stack_pointer(void) { unsigned long sp; asm("mov sp,%0; ":"=r" (sp)); return sp; } Could anyone help me in explaining the current_stack_pointer and (current_stack_pointer & ~(THREAD_SIZE - 1)) calculation? This is not as mentioned in the book. If page size is 4KB and 2 page per process kernel stack is used then THREAD_Size will be 8KB. Thanks, Vijay