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On 11/18/2016 10:07 AM, Dan Williams wrote:
On Fri, Nov 18, 2016 at 8:47 AM, Dave Jiang
<dave.jiang(a)intel.com>
wrote:
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>
>
> On 11/18/2016 04:33 AM, Thomas Gleixner wrote:
>> On Thu, 17 Nov 2016, Dave Jiang wrote:
>>> CONFIG_RANDOMIZE_BASE can place the kernel anywhere. This
>>> causes a problem for when memmap=nn!ss is used. This
>>> information is not known until after the kernel starts
>>> executing and the decision for where the randomized base goes
>>> happens before the kernel is uncompressed. memmap=nn!ss is
>>> not reliable in the presence of CONFIG_RANDOMIZE_BASE.
>>
>> So this is a description of a problem. Now what's missing is a
>> useful explanation why you think that adding a warning will
>> make things better.
>>
>> IMNSHO adding that warning is just a pointless exercise.
>>
>> Why aren't you addressing the real issue and make the boot
>> code parse that option and prevent that region from being used
>> for kernel placement?
>>
>> The same issue exists for other memmap options as well, not
>> just for that PMEM thingy.
>>
>> Thanks,
>>
>> tglx
>>
>
> I wasn't planning to fix it because the pmem memmap option is
> really only used for testing. Is it possible to parse the kernel
> commandline parameters before the kernel is uncompressed?
Apologies, this was my mistake. I missed that we have early boot
command line parsing in addition to the in-kernel cmdline parsing.
Dave, I think we could fix this in:
arch/x86/boot/compressed/kaslr.c::choose_random_location().
Actually it was my fault. I was digging around that and somehow
totally missed the early command line parsing bits.
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