Date: Fri, 7 Dec 2018 15:14:53 -0500 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: aio_cancel segmentation fault for in progress write requests On Fri, Dec 07, 2018 at 09:06:18PM +0100, Florian Weimer wrote: > * Rich Felker: > > > I don't think so. I'm concerned that it's a stack overflow, and that > > somehow the kernel folks have managed to break the MINSIGSTKSZ ABI. > > Probably: > > <https://sourceware.org/bugzilla/show_bug.cgi?id=20305> > <https://sourceware.org/bugzilla/show_bug.cgi?id=22636> > > It's a nasty CPU backwards compatibility problem. Some of the > suggestions I made to work around this are simply wrong; don't take them > too seriously. > > Nowadays, the kernel has a way to disable the %zmm registers, but it > unfortunately does not reduce the save area size. How large is the saved context with the %zmm junk? I measured just ~768 bytes on normal x86_64 without it, and since 2048 is rounded up to a whole page (4096), overflow should not happen until the signal context is something like 3.5k (allowing ~512 bytes for TCB (~128) and 2 simple call frames). Rich
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