Re: Why system call need to copy the date from the userspace before using it

Hacksaw
2005-04-13T12:00:09Z

>>Why not use it directly
>Some of these reasons are:

It seems like you gave reason why userland pointers shouldn't be trusted, not
why userland data should be copied into kernel land. All the problems you
mentioned would have to be solved by the kernel regardless of copying the data
around.

Ummm... Except for the who's mapped now problem. That's pretty weird. I guess
that's something that comes with trying to use tons of RAM in a 32 bit system.

I thought the big issue was the need to lock the page(s) during the call, and
maybe some tricky races which made the idea difficult.
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