Re: ptrace can't be transparent on readonly MAP_SHARED

[Linus Torvalds]

On Thu, 15 Sep 2005, Andrea Arcangeli wrote:

> On Thu, Sep 15, 2005 at 08:12:59AM -0700, Linus Torvalds wrote:
> > have a PROT_READONLY/PROT_NONE area that is visible from the debugger, but
> > continues to cause SIGSEGV's if the user process itself tries to access
> > it. To me, that's good.
> 
> Continue to cause sigsegv yes, but on the wrong page, when it will read
> the page it can contain different data compared to what is on
> disk/pagecache.

So? You're not making any sense.

I repeat: we CANNOT AVOID the fact that we will do COW.

That COW is required. No way we can avoid it. It has _nothing_ to do with 
maybe_mkwrite().

So I don't know why you continually refuse to just admit that fact. Why do 
you mix up the COW semantics with the maybe_mkwrite() semantics.

If you can't argue against maybe_mkwrite() without involving the COW
argument, then stop arguing. They are two totally different thigns.

		Linus
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