Messages in this thread | | | Date | Wed, 4 Jan 2017 09:57:45 +0800 | From | Baoquan He <> | Subject | Re: [PATCH] x86: fix kaslr and memmap collision |
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On 01/03/17 at 01:15pm, Dave Jiang wrote: > > > On 01/03/2017 11:24 AM, Dan Williams wrote: > > On Tue, Jan 3, 2017 at 12:31 AM, Baoquan He <bhe@redhat.com> wrote: > >> Hi Dan, > >> > >> On 11/22/16 at 09:26am, Dan Williams wrote: > >>> [ replying for Dave since he's offline today and tomorrow ] > >>> > >>> On Tue, Nov 22, 2016 at 12:47 AM, Ingo Molnar <mingo@kernel.org> wrote: > >>>> > >>>> * Dave Jiang <dave.jiang@intel.com> wrote: > >>>> > >>>>> CONFIG_RANDOMIZE_BASE relocates the kernel to a random base address. > >>>>> However it does not take into account the memmap= parameter passed in from > >>>>> the kernel commandline. > >>>> > >>>> memmap= parameters are often used as a list. > >>>> > >>>>> [...] This results in the kernel sometimes being put in the middle of the user > >>>>> memmap. [...] > >>>> > >>>> What does this mean? If memmap= is used to re-define the memory map then the > >>>> kernel getting in the middle of a RAM area is what we want, isn't it? What we > >>>> don't want is for the kernel to get into reserved areas, right? > >>> > >>> Right, this is about teaching kaslr to not land the kernel in newly > >>> defined reserved regions that were not marked reserved in the initial > >>> e820 map from platform firmware. > >> > >> If only tell kaslr to not land kernel in newly defined reserved regions, > >> memory added by "memmap=nn[KMG]@ss[KMG]" should not be avoided since > >> it's usable memory. Kernel randomized into this region is also what we > >> want. Not sure if I understand it right. > > > > You're right, this is supposed to be for memmap=nn!ss cases which > > defines reserved persistent memory ranges, not memmap=nn@ss which > > defines usable memory. > > > > We need to fix mem_avoid_memmap() to only skip memmap= statements that > > specify reserved memory.
Thanks for confirmation, Dan!
> > > > I think nn@ss is the only one that we should skip over, otherwise > everything else looks like should be avoided. I'll update. Hi Dave,
I guess your purpose is to avoid the user defined reserved memory and pmem which I am not very sure about since kaslr won't stamp on ACPI region reported by BIOS. Seems OK to avoid them all except of nn@ss.
I have other concerns, will directly comment in your v4 post.
Thanks Baoquan
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