[PATCH v5sub1 7/8] arm64: move kernel image to base of vmalloc area

[Ard Biesheuvel]

On 12 February 2016 at 15:58, Catalin Marinas <catalin.marinas at arm.com> wrote:
> Hi Ard,
>
> On Mon, Feb 01, 2016 at 11:54:52AM +0100, Ard Biesheuvel wrote:
>> This moves the module area to right before the vmalloc area, and
>> moves the kernel image to the base of the vmalloc area. This is
>> an intermediate step towards implementing KASLR, which allows the
>> kernel image to be located anywhere in the vmalloc area.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>
> This patch is causing lots of KASAN warnings on Juno (interestingly, it
> doesn't seem to trigger on Seattle, though we only tried for-next/core).
> I pushed the branch that I'm currently using here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux for-next/kernmap
>
>
> A typical error (though its place varies based on the config options,
> kernel layout):
>
> BUG: KASAN: stack-out-of-bounds in clockevents_program_event+0x28/0x1b0 at addr ffffffc936257cc8

Can you confirm that these are stack accesses? I was having similar
errors before, and I ended up creating the kasan zero page patch
because it turned out the kasan shadow page in question was aliased
and the stack writes were occurring elsewhere.


> Read of size 8 by task swapper/2/0
> page:ffffffbde6d895c0 count:0 mapcount:0 mapping:          (null) index:0x0
> flags: 0x4000000000000000()
> page dumped because: kasan: bad access detected
> CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.5.0-rc1+ #130
> Hardware name: Juno (DT)
> Call trace:
> [<ffffff900408b590>] dump_backtrace+0x0/0x258
> [<ffffff900408b7fc>] show_stack+0x14/0x20
> [<ffffff900448789c>] dump_stack+0xac/0x100
> [<ffffff9004224f3c>] kasan_report_error+0x544/0x570
> [<ffffff9004225328>] kasan_report+0x40/0x48
> [<ffffff9004223c58>] __asan_load8+0x60/0x78
> [<ffffff90041596f0>] clockevents_program_event+0x28/0x1b0
> [<ffffff900415c63c>] tick_program_event+0x74/0xb8
> [<ffffff9004148944>] __remove_hrtimer+0xcc/0x100
> [<ffffff9004148f0c>] hrtimer_start_range_ns+0x3f4/0x538
> [<ffffff900415d450>] __tick_nohz_idle_enter+0x558/0x590
> [<ffffff900415d74c>] tick_nohz_idle_enter+0x44/0x78
> [<ffffff900411fcc8>] cpu_startup_entry+0x48/0x2c0
> [<ffffff9004091f58>] secondary_start_kernel+0x208/0x278
> [<0000000080082aac>] 0x80082aac
> Memory state around the buggy address:
>  ffffffc936257b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffffffc936257c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1
>>ffffffc936257c80: f1 f1 00 00 00 00 f3 f3 f3 f3 00 00 00 00 00 00
>                                               ^
>  ffffffc936257d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffffffc936257d80: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
>
>
> And some additional info from the kernel boot:
>
> Processing EFI memory map:
>   0x000008000000-0x00000bffffff [Memory Mapped I/O  |RUN|  |  |  |  |  |   |  |  |  |UC]
>   0x00001c170000-0x00001c170fff [Memory Mapped I/O  |RUN|  |  |  |  |  |   |  |  |  |UC]
>   0x000080000000-0x00008000ffff [Loader Data        |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x000080010000-0x00008007ffff [Conventional Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x000080080000-0x00008149ffff [Loader Data        |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0000814a0000-0x00009fdfffff [Conventional Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x00009fe00000-0x00009fe0ffff [Loader Data        |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x00009fe10000-0x0000dfffffff [Conventional Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0000e00f0000-0x0000febd5fff [Conventional Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0000febd6000-0x0000febd9fff [ACPI Reclaim Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]*
>   0x0000febda000-0x0000febdafff [ACPI Memory NVS    |   |  |  |  |  |  |   |WB|WT|WC|UC]*
>   0x0000febdb000-0x0000febdcfff [ACPI Reclaim Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]*
>   0x0000febdd000-0x0000feffffff [Boot Data          |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x000880000000-0x0009f8794fff [Conventional Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009f8795000-0x0009f8796fff [Loader Data        |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009f8797000-0x0009f9bb4fff [Loader Code        |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009f9bb5000-0x0009faf6efff [Boot Code          |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009faf6f000-0x0009fafa9fff [Runtime Data       |RUN|  |  |  |  |  |   |WB|WT|WC|UC]*
>   0x0009fafaa000-0x0009ff2b1fff [Conventional Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009ff2b2000-0x0009ffb70fff [Boot Data          |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009ffb71000-0x0009ffb89fff [Conventional Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009ffb8a000-0x0009ffb8dfff [Boot Data          |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009ffb8e000-0x0009ffb8efff [Conventional Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009ffb8f000-0x0009ffdddfff [Boot Data          |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009ffdde000-0x0009ffe76fff [Conventional Memory|   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009ffe77000-0x0009fff6dfff [Boot Code          |   |  |  |  |  |  |   |WB|WT|WC|UC]
>   0x0009fff6e000-0x0009fffaefff [Runtime Code       |RUN|  |  |  |  |  |   |WB|WT|WC|UC]*
>   0x0009fffaf000-0x0009ffffefff [Runtime Data       |RUN|  |  |  |  |  |   |WB|WT|WC|UC]*
>   0x0009fffff000-0x0009ffffffff [Boot Data          |   |  |  |  |  |  |   |WB|WT|WC|UC]
>
>
> Memory: 7068520K/8371264K available (10424K kernel code, 3464K rwdata, 5284K rodata, 1016K init, 380K bss, 1286360K reserved, 16384K cma-reserved)
> Virtual kernel memory layout:
>     kasan   : 0xffffff8000000000 - 0xffffff9000000000   (    64 GB)
>     modules : 0xffffff9000000000 - 0xffffff9004000000   (    64 MB)
>     vmalloc : 0xffffff9004000000 - 0xffffffbdbfff0000   (   182 GB)
>       .init : 0xffffff9004fd9000 - 0xffffff90050d7000   (  1016 KB)
>       .text : 0xffffff9004080000 - 0xffffff9004fd9000   ( 15716 KB)
>       .data : 0xffffff90050d7000 - 0xffffff9005439200   (  3465 KB)
>     vmemmap : 0xffffffbdc0000000 - 0xffffffbfc0000000   (     8 GB maximum)
>               0xffffffbdc2000000 - 0xffffffbde8000000   (   608 MB actual)
>     fixed   : 0xffffffbffe7fd000 - 0xffffffbffec00000   (  4108 KB)
>     PCI I/O : 0xffffffbffee00000 - 0xffffffbfffe00000   (    16 MB)
>     memory  : 0xffffffc000000000 - 0xffffffc980000000   ( 38912 MB)
>
> --
> Catalin