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SubjectRe: [RFC PATCH 00/10] implement KASLR for powerpc/fsl_booke/32
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On 2019/7/26 15:04, Diana Madalina Craciun wrote:
> Hi Jason,
>
> I have briefly tested yesterday on a P4080 board and did not see any
> issues. I do not have much expertise on KASLR, but I will take a look
> over the code.
>

Hi Diana, thanks. Looking forward to your suggestions.

> Regards,
> Diana
>
> On 7/25/2019 10:16 AM, Jason Yan wrote:
>> Hi all, any comments?
>>
>>
>> On 2019/7/17 16:06, Jason Yan wrote:
>>> This series implements KASLR for powerpc/fsl_booke/32, as a security
>>> feature that deters exploit attempts relying on knowledge of the location
>>> of kernel internals.
>>>
>>> Since CONFIG_RELOCATABLE has already supported, what we need to do is
>>> map or copy kernel to a proper place and relocate. Freescale Book-E
>>> parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1
>>> entries are not suitable to map the kernel directly in a randomized
>>> region, so we chose to copy the kernel to a proper place and restart to
>>> relocate.
>>>
>>> Entropy is derived from the banner and timer base, which will change every
>>> build and boot. This not so much safe so additionally the bootloader may
>>> pass entropy via the /chosen/kaslr-seed node in device tree.
>>>
>>> We will use the first 512M of the low memory to randomize the kernel
>>> image. The memory will be split in 64M zones. We will use the lower 8
>>> bit of the entropy to decide the index of the 64M zone. Then we chose a
>>> 16K aligned offset inside the 64M zone to put the kernel in.
>>>
>>> KERNELBASE
>>>
>>> |--> 64M <--|
>>> | |
>>> +---------------+ +----------------+---------------+
>>> | |....| |kernel| | |
>>> +---------------+ +----------------+---------------+
>>> | |
>>> |-----> offset <-----|
>>>
>>> kimage_vaddr
>>>
>>> We also check if we will overlap with some areas like the dtb area, the
>>> initrd area or the crashkernel area. If we cannot find a proper area,
>>> kaslr will be disabled and boot from the original kernel.
>>>
>>> Jason Yan (10):
>>> powerpc: unify definition of M_IF_NEEDED
>>> powerpc: move memstart_addr and kernstart_addr to init-common.c
>>> powerpc: introduce kimage_vaddr to store the kernel base
>>> powerpc/fsl_booke/32: introduce create_tlb_entry() helper
>>> powerpc/fsl_booke/32: introduce reloc_kernel_entry() helper
>>> powerpc/fsl_booke/32: implement KASLR infrastructure
>>> powerpc/fsl_booke/32: randomize the kernel image offset
>>> powerpc/fsl_booke/kaslr: clear the original kernel if randomized
>>> powerpc/fsl_booke/kaslr: support nokaslr cmdline parameter
>>> powerpc/fsl_booke/kaslr: dump out kernel offset information on panic
>>>
>>> arch/powerpc/Kconfig | 11 +
>>> arch/powerpc/include/asm/nohash/mmu-book3e.h | 10 +
>>> arch/powerpc/include/asm/page.h | 7 +
>>> arch/powerpc/kernel/Makefile | 1 +
>>> arch/powerpc/kernel/early_32.c | 2 +-
>>> arch/powerpc/kernel/exceptions-64e.S | 10 -
>>> arch/powerpc/kernel/fsl_booke_entry_mapping.S | 23 +-
>>> arch/powerpc/kernel/head_fsl_booke.S | 61 ++-
>>> arch/powerpc/kernel/kaslr_booke.c | 439 ++++++++++++++++++
>>> arch/powerpc/kernel/machine_kexec.c | 1 +
>>> arch/powerpc/kernel/misc_64.S | 5 -
>>> arch/powerpc/kernel/setup-common.c | 23 +
>>> arch/powerpc/mm/init-common.c | 7 +
>>> arch/powerpc/mm/init_32.c | 5 -
>>> arch/powerpc/mm/init_64.c | 5 -
>>> arch/powerpc/mm/mmu_decl.h | 10 +
>>> arch/powerpc/mm/nohash/fsl_booke.c | 8 +-
>>> 17 files changed, 580 insertions(+), 48 deletions(-)
>>> create mode 100644 arch/powerpc/kernel/kaslr_booke.c
>>>
>>
>
>
> .
>

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