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

On Fri, Feb 12, 2016 at 04:02:58PM +0100, Ard Biesheuvel wrote:

On 12 February 2016 at 15:58, Catalin Marinas [off-list ref] wrote:

quoted

Hi Ard,

On Mon, Feb 01, 2016 at 11:54:52AM +0100, Ard Biesheuvel wrote:

quoted

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 <redacted>

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.

It's possible, we are looking into this. Is there any other patch I miss on
the above branch?

BTW, disabling CPU_IDLE, I get other errors:

WARNING: at /work/Linux/linux-2.6-aarch64/mm/vmalloc.c:135
Modules linked in:

CPU: 2 PID: 973 Comm: systemd-modules Tainted: G        W       4.5.0-rc1+ #131
Hardware name: Juno (DT)
task: ffffffc93448e200 ti: ffffffc9346ac000 task.ti: ffffffc9346ac000
PC is at vmap_page_range_noflush+0x240/0x2e8
LR is at vmap_page_range_noflush+0x16c/0x2e8
pc : [<ffffff90041fef78>] lr : [<ffffff90041feea4>] pstate: 20000145
sp : ffffffc9346af9b0
x29: ffffffc9346af9b0 x28: ffffff90050da000
x27: ffffffc001438008 x26: ffffffbde6d16440
x25: 0000004240000000 x24: ffffffc97ff3a000
x23: 0000000000000041 x22: ffffffc078e9e600
x21: ffffff8200002000 x20: ffffff8200001000
x19: 0000000000000000 x18: 00000000f3294c2f
x17: 00000000f7dc90fb x16: 0000000087b402ce
x15: ffffffffffffffff x14: ffffff0000000000
x13: ffffffffffffffff x12: 0000000000000028
x11: 0101010101010101 x10: 00000001801a001a
x9 : 0000000000000000 x8 : ffffff89268b2400
x7 : 0000000000000000 x6 : 000000000000003f
x5 : 0000000000000040 x4 : 0000000000000000
x3 : 0000000000000000 x2 : 1ffffff800287001
x1 : dfffff9000000000 x0 : 00e8000081439713

---[ end trace 8a78d7ad8d08d2a9 ]---
Call trace:
Exception stack(0xffffffc9346af790 to 0xffffffc9346af8b0)
f780:                                   0000000000000000 ffffff8200001000
f7a0: ffffffc9346af9b0 ffffff90041fef78 0000000020000145 000000000000003d
f7c0: 0000004240000000 ffffffc078e9f600 0000000041b58ab3 ffffff9004f0c370
f7e0: ffffff9004082608 ffffffc078e9f620 00000000024080c2 0000000000400000
f800: ffffffc9346afe70 ffffffc9346afe50 ffffffc9346af9b0 ffffffc93448e200
f820: ffffffc9346af830 ffffff900408b1b0 ffffffc9346af900 ffffff900408b228
f840: ffffffc9346ac000 ffffffc9346af9b0 ffffffc9346ac000 ffffffc078e9e600
f860: 0000000041b58ab3 ffffff9004f0c8a8 ffffff900408b080 000000010010000e
f880: ffffffc9346af9b0 0000000000000000 00e8000081439713 dfffff9000000000
f8a0: 1ffffff800287001 0000000000000000
[<ffffff90041fef78>] vmap_page_range_noflush+0x240/0x2e8
[<ffffff90041ff078>] map_vm_area+0x58/0x88
[<ffffff9004200400>] __vmalloc_node_range+0x2b8/0x350
[<ffffff9004224394>] kasan_module_alloc+0x64/0xb8
[<ffffff90040943f4>] module_alloc+0x5c/0xa0
[<ffffff9004169460>] load_module+0x1798/0x3098
[<ffffff900416b020>] SyS_finit_module+0xf8/0x108
[<ffffff9004085d30>] el0_svc_naked+0x24/0x28
vmalloc: allocation failure, allocated 4096 of 4096 bytes

-- 
Catalin