On Mon, Nov 13, 2017 at 10:20:06AM +0100, Michal Hocko wrote: > [Cc arm and ppc maintainers] > > Thanks a lot for testing! > > On Sun 12-11-17 11:38:02, Joel Stanley wrote: > > On Fri, Nov 10, 2017 at 11:00 PM, Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > Hi Joel, > > > > > > On Wed 08-11-17 15:20:50, Michal Hocko wrote: > > > [...] > > >> > There are a lot of messages on the way up that look like this: > > >> > > > >> > [ 2.527460] Uhuuh, elf segement at 000d9000 requested but the > > >> > memory is mapped already > > >> > [ 2.540160] Uhuuh, elf segement at 000d9000 requested but the > > >> > memory is mapped already > > >> > [ 2.546153] Uhuuh, elf segement at 000d9000 requested but the > > >> > memory is mapped already > > >> > > > >> > And then trying to run userspace looks like this: > > >> > > >> Could you please run with debugging patch posted > > >> http://lkml.kernel.org/r/20171107102854.vylrtaodla63kc57@xxxxxxxxxxxxxx > > > > > > Did you have chance to test with this debugging patch, please? > > > > Lots of this: > > > > [ 1.177266] Uhuuh, elf segement at 000d9000 requested but the memory is mapped already, got 000dd000 > > [ 1.177555] Clashing vma [dd000, de000] flags:100873 name:(null) > > This smells like the problem I've expected that mmap with hint doesn't > respect the hint even though there is no clashing mapping. The above > basically says that we didn't map at 0xd9000 but it has placed it at > 0xdd000. The nearest (clashing) vma is at 0xdd000 so this is our new > mapping. find_vma returns the closest vma (with addr < vm_end) for the > given address 0xd9000 so this address cannot be mapped by any other vma. > > Now that I am looking at arm's arch_get_unmapped_area it does perform > aligning for shared vmas. We do not do that for MAP_FIXED. Powepc, > reported earlier [1] seems to suffer from the similar problem. > slice_get_unmapped_area alignes to slices, whatever that means. > > I can see two possible ways around that. Either we explicitly request > non-aligned mappings via a special MAP_$FOO (e.g. MAP_FIXED_SAFE) or > simply opt out from the MAP_FIXED protection via ifdefs. The first > option sounds more generic to me but also more tricky to not introduce > other user visible effects. The later is quite straightforward. What do > you think about the following on top of the previous patch? > > It is rather terse and disables the MAP_FIXED protection for arm > comletely because I couldn't find a way to make it conditional on > CACHEID_VIPT_ALIASING. But this can be always handled later. I find the > protection for other archtectures useful enough to have this working for > most architectures now and handle others specially. Can someone provide the background information for this please? -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up According to speedtest.net: 8.21Mbps down 510kbps up -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
