On 11.10.2018 11:36, Peter Maydell wrote: > On 11 October 2018 at 00:55, Brad Smith <b...@comstyle.com> wrote: >> And from FreeBSD... >> >> MAP_STACK MAP_STACK implies MAP_ANON, and offset of 0. The fd >> argument must be -1 and prot must include at least >> PROT_READ and PROT_WRITE. >> >> This option creates a memory region that grows to at >> most len bytes in size, starting from the stack top >> and growing down. The stack top is the starting >> address returned by the call, plus len bytes. The >> bottom of the stack at maximum growth is the starting >> address returned by the call. >> >> Stacks created with MAP_STACK automatically grow. >> Guards prevent inadvertent use of the regions into >> which those stacks can grow without requiring mapping >> the whole stack in advance. > > Hmm. That "automatically growing" part sounds like > behaviour we definitely do not want for our use case. > So we're going to need to make this OS-specific :-( >
I propose to restrict MAP_STACK it to OpenBSD (with a comment in the code). Once it will be needed by someone else will be able to enable it for other OSes. > thanks > -- PMM >
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