>> As revealed by the recent "Prevent data exception in kernel space" >> patch, versions of glibc prior to 2.4[1] assume that, on >> powerpc32, they >> can execute out of any readable mapping, regardless of whether it is >> marked for execution. This happens in the elf_machine_load_address() >> function. > > Umm, are you sure about this? The "prevent data exception in kernel > space" patch came from a test program I had that attempted to > execute a > page with /no permissions/ at all!
I haven't looked at the code path in detail, but I believe Scott's analysis is correct. The kernel would merrily let a program run code from a page without execute permission (so also from a page without any permissions at all); not anymore, after my patch. Programs relying on this behaviour are obviously buggy, but the problem is that one of these broken programs is glibc, at least some not-all-that-new but also not-all-that-old versions. > I know that I used to have problems with mono making this > assumption but > these have since been fixed; however if I understand you correctly > then > you can always pre-fault the page by a read and then execute it so I > don't see the point in not doing the change you suggest. Too many negatives, I don't see which way you're arguing :-) I think you're saying to treat read access as including execute access? I believe that would be too permissive here. Anyway, let's first decide what is the right thing to do, and only then look at the code ;-) Segher _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
