* Zachary Amsden (zach@xxxxxxxxxx) wrote: > Chris Wright wrote: > >* Zachary Amsden (zach@xxxxxxxxxx) wrote: > > > >>Allow creation of an compile time hole at the top of linear address space. > >> > >>Extended to allow a dynamic hole in linear address space, 7/2005. This > >>required some serious hacking to get everything perfect, but the end > >>result > >>appears to function quite nicely. Everyone can now share the appreciation > >>of pseudo-undocumented ELF OS fields, which means core dumps, debuggers > >>and even broken or obsolete linkers may continue to work. > >> > > > >Thanks. Gerd did something similar (although I believe it's simpler, > >don't recall the relocation magic) for Xen. Either way, it's useful > >from Xen perspective. > > I believe Xen disables sysenter. Yes, so vsyscall page has int80 implementation. > The complications in my patch come > from the fact that the vsyscall page has to be relocated dynamically, > requiring, basically run time linking on the page and some tweaks to get > sysenter to work. If you don't use vsyscall (say, non-TLS glibc), then > you don't need that complexity. But I think it might be needed now, > even for Xen. I believe both Xen and execshield move vsyscall out of fixmap, and then map into userspace as normal vma. thanks, -chris
