On 01/20/2015 07:37 PM, Baoquan He 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. > > 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? >
I have no idea what the #PF thing you're referring to is, but I have code to implement a #PF handler in boot/compressed if it would be helpful. It's two patches: https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=sync_rand_seed&id=89476ea6a2becbaee4f45c3b6689ff31b6aa959a https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=sync_rand_seed&id=142d86921e6f271261584016fc8cfa5cdbf455ba You can't recover from a page fault in my version of this code, but that would be straightforward to add. --Andy -- 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/
