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From:   Diana Madalina Craciun <diana.craciun@nxp.com>
To:     Jason Yan <yanaijie@huawei.com>,
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Subject: Re: [RFC PATCH 00/10] implement KASLR for powerpc/fsl_booke/32
Thread-Topic: [RFC PATCH 00/10] implement KASLR for powerpc/fsl_booke/32
Thread-Index: AQHVPHQmPxsZ5ebrqkOb0IKUtKxd9g==
Date:   Fri, 26 Jul 2019 07:04:31 +0000
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Hi Jason,=0A=
=0A=
I have briefly tested yesterday on a P4080 board and did not see any=0A=
issues. I do not have much expertise on KASLR, but I will take a look=0A=
over the code.=0A=
=0A=
Regards,=0A=
Diana=0A=
=0A=
On 7/25/2019 10:16 AM, Jason Yan wrote:=0A=
> Hi all, any comments?=0A=
>=0A=
>=0A=
> On 2019/7/17 16:06, Jason Yan wrote:=0A=
>> This series implements KASLR for powerpc/fsl_booke/32, as a security=0A=
>> feature that deters exploit attempts relying on knowledge of the locatio=
n=0A=
>> of kernel internals.=0A=
>>=0A=
>> Since CONFIG_RELOCATABLE has already supported, what we need to do is=0A=
>> map or copy kernel to a proper place and relocate. Freescale Book-E=0A=
>> parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1=0A=
>> entries are not suitable to map the kernel directly in a randomized=0A=
>> region, so we chose to copy the kernel to a proper place and restart to=
=0A=
>> relocate.=0A=
>>=0A=
>> Entropy is derived from the banner and timer base, which will change eve=
ry=0A=
>> build and boot. This not so much safe so additionally the bootloader may=
=0A=
>> pass entropy via the /chosen/kaslr-seed node in device tree.=0A=
>>=0A=
>> We will use the first 512M of the low memory to randomize the kernel=0A=
>> image. The memory will be split in 64M zones. We will use the lower 8=0A=
>> bit of the entropy to decide the index of the 64M zone. Then we chose a=
=0A=
>> 16K aligned offset inside the 64M zone to put the kernel in.=0A=
>>=0A=
>>      KERNELBASE=0A=
>>=0A=
>>          |-->   64M   <--|=0A=
>>          |               |=0A=
>>          +---------------+    +----------------+---------------+=0A=
>>          |               |....|    |kernel|    |               |=0A=
>>          +---------------+    +----------------+---------------+=0A=
>>          |                         |=0A=
>>          |----->   offset    <-----|=0A=
>>=0A=
>>                                kimage_vaddr=0A=
>>=0A=
>> We also check if we will overlap with some areas like the dtb area, the=
=0A=
>> initrd area or the crashkernel area. If we cannot find a proper area,=0A=
>> kaslr will be disabled and boot from the original kernel.=0A=
>>=0A=
>> Jason Yan (10):=0A=
>>    powerpc: unify definition of M_IF_NEEDED=0A=
>>    powerpc: move memstart_addr and kernstart_addr to init-common.c=0A=
>>    powerpc: introduce kimage_vaddr to store the kernel base=0A=
>>    powerpc/fsl_booke/32: introduce create_tlb_entry() helper=0A=
>>    powerpc/fsl_booke/32: introduce reloc_kernel_entry() helper=0A=
>>    powerpc/fsl_booke/32: implement KASLR infrastructure=0A=
>>    powerpc/fsl_booke/32: randomize the kernel image offset=0A=
>>    powerpc/fsl_booke/kaslr: clear the original kernel if randomized=0A=
>>    powerpc/fsl_booke/kaslr: support nokaslr cmdline parameter=0A=
>>    powerpc/fsl_booke/kaslr: dump out kernel offset information on panic=
=0A=
>>=0A=
>>   arch/powerpc/Kconfig                          |  11 +=0A=
>>   arch/powerpc/include/asm/nohash/mmu-book3e.h  |  10 +=0A=
>>   arch/powerpc/include/asm/page.h               |   7 +=0A=
>>   arch/powerpc/kernel/Makefile                  |   1 +=0A=
>>   arch/powerpc/kernel/early_32.c                |   2 +-=0A=
>>   arch/powerpc/kernel/exceptions-64e.S          |  10 -=0A=
>>   arch/powerpc/kernel/fsl_booke_entry_mapping.S |  23 +-=0A=
>>   arch/powerpc/kernel/head_fsl_booke.S          |  61 ++-=0A=
>>   arch/powerpc/kernel/kaslr_booke.c             | 439 ++++++++++++++++++=
=0A=
>>   arch/powerpc/kernel/machine_kexec.c           |   1 +=0A=
>>   arch/powerpc/kernel/misc_64.S                 |   5 -=0A=
>>   arch/powerpc/kernel/setup-common.c            |  23 +=0A=
>>   arch/powerpc/mm/init-common.c                 |   7 +=0A=
>>   arch/powerpc/mm/init_32.c                     |   5 -=0A=
>>   arch/powerpc/mm/init_64.c                     |   5 -=0A=
>>   arch/powerpc/mm/mmu_decl.h                    |  10 +=0A=
>>   arch/powerpc/mm/nohash/fsl_booke.c            |   8 +-=0A=
>>   17 files changed, 580 insertions(+), 48 deletions(-)=0A=
>>   create mode 100644 arch/powerpc/kernel/kaslr_booke.c=0A=
>>=0A=
>=0A=
=0A=