On Fri, Nov 18, 2016 at 8:47 AM, Dave Jiang <[email protected]> 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().
