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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:   Mon, 29 Jul 2019 14:30:15 +0000
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Reviewed-by: Diana Craciun <diana.craciun@nxp.com>=0A=
Tested-by: Diana Craciun <diana.craciun@nxp.com>=0A=
=0A=
=0A=
On 7/17/2019 10:49 AM, 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 location=
=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 ever=
y=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=