Date: Tue, 29 Jul 1997 20:33:55 -0700 From: David Greenman <dg@root.com> To: Michael Smith <msmith@atrad.adelaide.edu.au> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Location of copyin() and copyout().. Message-ID: <199707300333.UAA12396@implode.root.com> In-Reply-To: Your message of "Wed, 30 Jul 1997 12:52:18 %2B0930." <199707300322.MAA17715@genesis.atrad.adelaide.edu.au>
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>So, I write a function linux_i386_modify_ldt(), which lives in the >linux emulation module. It takes the Linux i386_modify_ldt() syscall, >converts the arguments to the right format, and tries to call >i386_set_ldt(). > >Only it _can't_, because the latter is using copyin(), and cannot access >the argument structure in kernel space. Ah, now I understand. Yes, copyin/out do page protection checking and will not allow a copyout to kernel memory or a copyin from kernel memory (since kernel memory is protected against users). -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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