On 11/21/2016 01:29 AM, Eugene Syromyatnikov wrote: > On Sun, Nov 20, 2016 at 9:39 PM, Michael Kerrisk (man-pages) > <mtk.manpages@xxxxxxxxx> wrote: >> Hello Eugene, >> >> I've applied this patch, and tweaked a few pieces, but need >> help on one point. >> >> On 11/20/2016 02:16 AM, Eugene Syromyatnikov wrote: [...] >>> +.B PROT_GROWSUP >>> +Apply protection mode up to the end of the mapping which grows up (it should be a >>> +stack segment on HP PA-RISC, since there are no other ways to map a segment with >>> +.B VM_GROWSUP >>> +even if architecture has support for it.) >> >> We need a different way to talk about VM_GROWSUP, since that is >> a detail internal to the kernel. Do you have a suggestion? > Well, it's difficult to say, because, while there is some support for > VMAs that grow up or down, there are little controls available from > userspace (judging by the code i've read). There's no way to perform > such mapping manually; on HP PA-RISC, it is done implicitly for stack, > as i understood, and on ia64 it should be used for register offload. > But the only handling present in mmap() is for > MAP_GROWSDOWN/MAP_DENYWRITE/MAP_LOCKED (calc_vm_flag_bits(); so, even > if MAP_GROWSUP definition is present on ia64, it can't be actually > used), and the VM_GROWSUP flag itself is arch-specific and defined > only on some arhitectures (pa-risc, metag and ia64) and used only as a > definition for VM_STACK. > > Maybe, just say "Apply protection mode up to the end of the mapping > which grows up (stack segment on HP PA-RISC and some other > architectures where it grows up and not down)", because there couldn't > be any other segments with this flag set. Thanks. I reworded along those lines. While looking at this stuff, I was also prompted to add some detail about MAP_GROWSDOWN to mmap(2). All changes pushed to Git. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
