On Mon, 9 Dec 2013, H.J. Lu wrote: > >> Normally, a PIE executable has zero virtual address on the first PT_LOAD > >> segment and kernel will load such executable at random address when > >> randomization is enabled. If randomization is disabled, kernel will load > >> it at a fixed address. But if a PIE executable has non-zero virtual > >> address on the first PT_LOAD segment, kernel will load such executable > >> at the non-zero virtual address when randomization is enabled. But when > >> randomization is disabled, kernel ignores the non-zero virtual address > >> at the non-zero virtual address when randomization is enabled. > > > > Hmm ... isn't actually this the thing that needs to be fixed instead? > > > > IOW, when randomization is enabled, is there a reason not to load on > > randomized address? (even if the first PT_LOAD segment has non-zero > > vaddr?) > > No, please don't do that. Normally, PIE has zero load address and kernel > can load it anywhere. There are multiple reasons why PIE has non-zero > load address. Saying you need to load a program above 4GB under x86-64, > you can't do that with normal dynamic executable. PIE with non-zero load > address is the only way to do that on x86-64.
Hmm, so if it's because of 4G PT_LOAD limit, how about at least adding randomized offset to the supplied vaddr? PT_LOAD being non-zero causing randomization to be turned off seems like quite unexpected behavior to me, with a great potential to cause a lot of confusion. -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
