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Re: Quick access to stack bounds


On 12/09/2009 12:23 PM, Roland McGrath wrote:
There are no heuristics, just rlimit constraints.
What could there be?  alloca(1<<20) is kosher.

Yes, and that's a problem With unlimited stacks and PROT_GROW* almost any invalid memory access can be interpreted to belong to a stack. This is why, I thought, there is something in the kernel to try to differentiate bogus accesses from extensions.



If you propose a kernel change get rid of PROT_GROWS* at the same time.

What do you have in mind?

As kernel extensions? Richard described the new AT_* constant to tell userlevel about the stack.



A mapping of RLIMIT_STACK size with a flag about
not precommitting any pages before faulting them in?

I was thinking about completely removing PROT_GROWS*. Nobody has used it in a decade, I bet.


The remaining issue then would be unlimited stacks.

--
â Ulrich Drepper â Red Hat, Inc. â 444 Castro St â Mountain View, CA â


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