Messages in this thread | | | From | Dan Williams <> | Date | Fri, 18 Nov 2016 09:07:41 -0800 | Subject | Re: [PATCH] x86: Add warning when memmap=nn!ss and CONFIG_RANDOMIZE_BASE enabled |
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On Fri, Nov 18, 2016 at 8:47 AM, Dave Jiang <dave.jiang@intel.com> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA256 > > > > 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().
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