init: How did init/do_mounts_rd.c overcome memory protection ?

From: Badhri Jagan Sridharan
Date: Tue Nov 10 2015 - 13:38:43 EST


Mighty upstream,

I see that do_mounts_rd.c seems to make calls to sys_read and
sys_lseek functions. As these are syscall functions, they expects
some of the arguments to be from userspace.

I was going through the article that Greg KH wrote a while back:
http://www.linuxjournal.com/article/8110?page=0,1 . I don't see any
references to set_fs/get_fs under init/*. Does the memory protection
get enabled only in the later stage ? Or does do_mounts_rd.c accomplish
this in some other way ?

Thanks,
Badhri
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