Hi Cheng... > As we know, the kernel thread has no user space, so it can't access > the user mode linear addresses. Actually, it can :) It borrows the user space part (task_struct->mm) of the last scheduled process. But since you can not predict which "mm" struct it will borrow, it is not recommended to do so.....however, this doesn't mean you absolutely can't :) >But when I traced the > call_usermodehelper() function, I found that the kernel thread use > kernel_thread() function to create another kernel > thread, and then the new kernel thread execute execve() function to > load the executable program of the user process. Why can it do this? > Can it access the user space? maybe what you saw was sys_execve (or do_execve?) ? In that case, no need to access user space since those functions are on kernel space (mapped on address larger than PAGE_OFFSET) regards, Mulyadi -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
