On Tue, Jan 20, 2015 at 7:37 PM, Baoquan He <b...@redhat.com> wrote: > Currently kaslr only randomize physical address of kernel loading, then add > the delta > to virtual address of kernel text mapping. Because kernel virtual address can > only be > from __START_KERNEL_map to > LOAD_PHYSICAL_ADDR+CONFIG_RANDOMIZE_BASE_MAX_OFFSET, namely > [0xffffffff80000000, 0xffffffffc0000000], so physical address can only be > randomized > in region [LOAD_PHYSICAL_ADDR, CONFIG_RANDOMIZE_BASE_MAX_OFFSET], namely > [16M, 1G]. > > So hpa and Vivek suggested the randomization should be done separately for > both physical > and virtual address. In this patchset I tried it. And after randomization, > relocation > handling only depends on virtual address changing, means I only check whether > virtual > address is randomized to other position, if yes relocation need be handled, > if no just > skip the relocation handling though physical address is randomized to > different place. > Now physical address can be randomized from 16M to 4G, virtual address offset > can be > from 16M to 1G.
This looks really great! Thanks for working on it! I'll wait to see what you find out about the #PF handler, and then I can start doing some testing too. -Kees > > Leftover problem: > hpa want to see the physical randomization can cover the whole physical > memory. I > checked code and found it's hard to do. Because in > arch/x86/boot/compressed/head_64.S > an identity mapping of 4G is built and then kaslr and decompressing are done. > The #PF > handler solution which he suggested is only available after jump into > decompressed > kernel, namely in arch/x86/kernel/head_64.S. I didn't think of a way to do > the whole > memory covering for physical address randomization, any suggestion or idea? > > Baoquan He (6): > remove a unused function parameter > a bug that relocation can not be handled when kernel is loaded above > 2G > Introduce a function to randomize the kernel text mapping address > adapt choose_kernel_location to add the kernel virtual address > randomzation > change the relocations behavior for kaslr on x86_64 > extend the upper limit of kernel physical address randomization to 4G > > arch/x86/boot/compressed/aslr.c | 69 > ++++++++++++++++++++++++++++------------- > arch/x86/boot/compressed/misc.c | 34 +++++++++++++------- > arch/x86/boot/compressed/misc.h | 20 ++++++------ > 3 files changed, 82 insertions(+), 41 deletions(-) > > -- > 1.9.3 > -- Kees Cook Chrome OS Security -- 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/
