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SubjectRe: [PATCH v6 00/12] implement KASLR for powerpc/fsl_booke/32
Hi Scott,

On 2019/8/28 12:05, Scott Wood wrote:
> On Fri, 2019-08-09 at 18:07 +0800, 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.
> Have you tested this with a kernel that was loaded at a non-zero address? I
> tried loading a kernel at 0x04000000 (by changing the address in the uImage,
> and setting bootm_low to 04000000 in U-Boot), and it works without
> CONFIG_RANDOMIZE and fails with.

How did you change the load address of the uImage, by changing the
kernel config CONFIG_PHYSICAL_START or the "-a/-e" parameter of mkimage?
I tried both, but it did not work with or without CONFIG_RANDOMIZE.


>> 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.
> How complicated would it be to directly access the HW RNG (if present) that
> early in the boot? It'd be nice if a U-Boot update weren't required (and
> particularly concerning that KASLR would appear to work without a U-Boot
> update, but without decent entropy).
> -Scott
> .

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