Jason Yan <yanaijie@xxxxxxxxxx> writes: > Hi Daniel, > > 在 2020/2/26 15:16, Daniel Axtens 写道: >> Hi Jason, >> >>> This is a try to implement KASLR for Freescale BookE64 which is based on >>> my earlier implementation for Freescale BookE32: >>> https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=131718 >>> >>> The implementation for Freescale BookE64 is similar as BookE32. One >>> difference is that Freescale BookE64 set up a TLB mapping of 1G during >>> booting. Another difference is that ppc64 needs the kernel to be >>> 64K-aligned. So we can randomize the kernel in this 1G mapping and make >>> it 64K-aligned. This can save some code to creat another TLB map at >>> early boot. The disadvantage is that we only have about 1G/64K = 16384 >>> slots to put the kernel in. >>> >>> KERNELBASE >>> >>> 64K |--> kernel <--| >>> | | | >>> +--+--+--+ +--+--+--+--+--+--+--+--+--+ +--+--+ >>> | | | |....| | | | | | | | | |....| | | >>> +--+--+--+ +--+--+--+--+--+--+--+--+--+ +--+--+ >>> | | 1G >>> |-----> offset <-----| >>> >>> kernstart_virt_addr >>> >>> I'm not sure if the slot numbers is enough or the design has any >>> defects. If you have some better ideas, I would be happy to hear that. >>> >>> Thank you all. >>> >> >> Are you making any attempt to hide kernel address leaks in this series? > > Yes. > >> I've just been looking at the stackdump code just now, and it directly >> prints link registers and stack pointers, which is probably enough to >> determine the kernel base address: >> >> SPs: LRs: %pS pointer >> [ 0.424506] [c0000000de403970] [c000000001fc0458] dump_stack+0xfc/0x154 (unreliable) >> [ 0.424593] [c0000000de4039c0] [c000000000267eec] panic+0x258/0x5ac >> [ 0.424659] [c0000000de403a60] [c0000000024d7a00] mount_block_root+0x634/0x7c0 >> [ 0.424734] [c0000000de403be0] [c0000000024d8100] prepare_namespace+0x1ec/0x23c >> [ 0.424811] [c0000000de403c60] [c0000000024d7010] kernel_init_freeable+0x804/0x880 >> >> git grep \\\"REG\\\" arch/powerpc shows a few other uses like this, all >> in process.c or in xmon. >> > > Thanks for reminding this. > >> Maybe replacing the REG format string in KASLR mode would be sufficient? >> > > Most archs have removed the address printing when dumping stack. Do we > really have to print this? > > If we have to do this, maybe we can use "%pK" so that they will be > hidden from unprivileged users. I suspect that you will find it easier to convince people to accept a change to %pK than removal :) BTW, I have a T4240RDB so I might be able to test this series at some point - do I need an updated bootloader to pass in a random seed, or is the kernel able to get enough randomness by itself? (Sorry if this is explained elsewhere in the series, I have only skimmed it lightly!) Regards, Daniel > > Thanks, > Jason > >> Regards, >> Daniel >> >> >>> v2->v3: >>> Fix build error when KASLR is disabled. >>> v1->v2: >>> Add __kaslr_offset for the secondary cpu boot up. >>> >>> Jason Yan (6): >>> powerpc/fsl_booke/kaslr: refactor kaslr_legal_offset() and >>> kaslr_early_init() >>> powerpc/fsl_booke/64: introduce reloc_kernel_entry() helper >>> powerpc/fsl_booke/64: implement KASLR for fsl_booke64 >>> powerpc/fsl_booke/64: do not clear the BSS for the second pass >>> powerpc/fsl_booke/64: clear the original kernel if randomized >>> powerpc/fsl_booke/kaslr: rename kaslr-booke32.rst to kaslr-booke.rst >>> and add 64bit part >>> >>> .../{kaslr-booke32.rst => kaslr-booke.rst} | 35 +++++++-- >>> arch/powerpc/Kconfig | 2 +- >>> arch/powerpc/kernel/exceptions-64e.S | 23 ++++++ >>> arch/powerpc/kernel/head_64.S | 14 ++++ >>> arch/powerpc/kernel/setup_64.c | 4 +- >>> arch/powerpc/mm/mmu_decl.h | 19 ++--- >>> arch/powerpc/mm/nohash/kaslr_booke.c | 71 +++++++++++++------ >>> 7 files changed, 132 insertions(+), 36 deletions(-) >>> rename Documentation/powerpc/{kaslr-booke32.rst => kaslr-booke.rst} (59%) >>> >>> -- >>> 2.17.2 >> >> . >>
