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.
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
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