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

>>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.
-- 
The key is realizing the whole world is stupid and being happy anyway
http://www.hacksaw.org -- http://www.privatecircus.com -- KB1FVD


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