On Thu, 14 Dec 2017, Peter Zijlstra wrote: > So here's a second posting of the VMA based LDT implementation; now without > most of the crazy. > > I took out the write fault handler and the magic LAR touching code. > > Additionally there are a bunch of patches that address generic vm issue. > > - gup() access control; In specific I looked at accessing !_PAGE_USER pages > because these patches rely on not being able to do that. > > - special mappings; A whole bunch of mmap ops don't make sense on special > mappings so disallow them. > > Both things make sense independent of the rest of the series. Similarly, the > patches that kill that rediculous LDT inherit on exec() are also unquestionably > good. > > So I think at least the first 6 patches are good, irrespective of the > VMA approach. > > On the whole VMA approach, Andy I know you hate it with a passion, but I really > rather like how it ties the LDT to the process that it belongs to and it > reduces the amount of 'special' pages in the whole PTI mapping. > > I'm not the one going to make the decision on this; but I figured I at least > post a version without the obvious crap parts of the last one. > > Note: if we were to also disallow munmap() for special mappings (which I > suppose makes perfect sense) then we could further reduce the actual LDT > code (we'd no longer need the sm::close callback and related things). That makes a lot of sense for the other special mapping users like VDSO and kprobes. Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
