Hi !
But the task_struct{}'s mm field of kernel thread is NULL. In another
word, kernel
thread has no user space address. However a user thread must have the user
space addresses, so where the mm struct of the user thread comes from when a
kernel thread becomes a user thread? I didn't find the code from
call_usermodehelper() function.
are you looking for this:
http://lxr.free-electrons.com/source/kernel/fork.c#511
?
you can see here that if we are calling not from process context,
we will have no mm struct (as you said),
therefore the process creation will fail...
(call_usermodehelper eventually reach do_fork, which calls copy_mm())
HTH.
if not please say :)
Ohad.
Thanks in advance!
Regards,
Cheng
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