From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Fri, 5 Feb 2016 17:46:49 +0000 Subject: [PATCH v5sub2 0/8] arm64: implement virtual KASLR In-Reply-To: References: <1454332178-4414-1-git-send-email-ard.biesheuvel@linaro.org> <20160205173248.GJ6076@e104818-lin.cambridge.arm.com> Message-ID: <20160205174649.GK6076@e104818-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Feb 05, 2016 at 06:38:33PM +0100, Ard Biesheuvel wrote: > On 5 February 2016 at 18:32, Catalin Marinas wrote: > > On Mon, Feb 01, 2016 at 02:35:03PM +0100, Ard Biesheuvel wrote: > >> On 1 February 2016 at 14:09, Ard Biesheuvel wrote: > >> > At the request of Catalin, this series has been split off from my series > >> > 'arm64: implement support for KASLR v4' [1]. This sub-series deals with > >> > creating a relocatable binary, and randomizing the virtual placement of > >> > the kernel itself, the modules and the linear region based on entropy > >> > supplied by the bootloader in the /chosen/kaslr-seed DT property. > >> > > >> > Changes since v4: > >> > - add randomization of the linear region, i.e., if the linear region is > >> > substantially larger than the space spanned by RAM, the mapping of RAM > >> > is moved to a random offset inside the linear region. > >> > - dropped the CRC check in kaslr_early_init(), since the only code that may > >> > modify .data through __fixmap_remap_fdt() is instrumentation that should > >> > deal with that correctly (For instance, the branch profiling records taken > >> > branches in structs allocated in .data, and these counts will not be reset > >> > to 0 between the first and the second call to __mmap_switched()) > >> > - add Mark's ack to patch #4 > >> > > >> > >> NOTE: I have omitted the relative kallsyms and relative extable > >> patches, since they already queued in akpm's tree. However, while the > >> kallsyms patch is merely an optimization, the extable patches are in > >> fact required for correct operation, since the build time sorting does > >> not work on absolute extables (this is due to the fact that the > >> resolution of the relocations is deferred until runtime, and so the > >> extable addresses are all zero at sorting time) > >> > >> http://ozlabs.org/~akpm/mmotm/broken-out/extable-add-support-for-relative-extables-to-search-and-sort-routines.patch > >> http://ozlabs.org/~akpm/mmotm/broken-out/arm64-switch-to-relative-exception-tables.patch > > > > I'm still trying to get my head around how we merge those. Since I > > assume akpm will push them during the merging window, part of your code > > cannot be tested before. > > Actually, my original idea was for akpm to take them as a late merge > after rebasing to -rc1, since they touch a variety of architectures, > but I am not sure if that came across. > > You could always take the series through your tree instead, I guess? They all have acks from maintainers, so that's an option. > > Can we deselect CONFIG_BUILDTIME_EXTABLE_SORT temporarily while we use > > absolute extable addresses? We patch them at boot-time and sort them > > at run-time. Once the above patches go in, we can revert to build-time > > extable sorting. > > I suppose that would be possible, but I simply haven't tried. I > noticed that ppc does not use build time extable sorting, that is why > they don't need to scripts/extable patch while they do use PIE > binaries. I did a quick check with: --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -22,7 +22,7 @@ config ARM64 select ARM_GIC_V3 select ARM_GIC_V3_ITS if PCI_MSI select ARM_PSCI_FW - select BUILDTIME_EXTABLE_SORT + select BUILDTIME_EXTABLE_SORT if !RELOCATABLE select CLONE_BACKWARDS select COMMON_CLK select CPU_PM if (SUSPEND || CPU_IDLE) and it seems that extable entries end up in the relocation symbols but I haven't fully checked the patching/sorting yet (it will probably be on Monday). -- Catalin