Re: [Resend][PATCH] x86/power/64: Always create temporary identity mapping correctly

On Mon, Aug 8, 2016 at 6:54 AM, Rafael J. Wysocki [off-list ref] wrote:

On Mon, Aug 8, 2016 at 3:40 PM, Borislav Petkov [off-list ref] wrote:

quoted

On Mon, Aug 08, 2016 at 03:31:31PM +0200, Rafael J. Wysocki wrote:

quoted

From: Rafael J. Wysocki <redacted>

The low-level resume-from-hibernation code on x86-64 uses
kernel_ident_mapping_init() to create the temoprary identity mapping,
but that function assumes that the offset between kernel virtual
addresses and physical addresses is aligned on the PGD level.

However, with a randomized identity mapping base, it may be aligned
on the PUD level and if that happens, the temporary identity mapping
created by set_up_temporary_mappings() will not reflect the actual
kernel identity mapping and the image restoration will fail as a
result (leading to a kernel panic most of the time).

To fix this problem, rework kernel_ident_mapping_init() to support
unaligned offsets between KVA and PA up to the PMD level and make
set_up_temporary_mappings() use it as approprtiate.

Reported-by: Thomas Garnier <redacted>

Reported-by: Borislav Petkov <redacted>

quoted

Suggested-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Rafael J. Wysocki <redacted>
Acked-by: Yinghai Lu <yinghai@kernel.org>
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This is sort of urgent, because hibernation doesn't work with KASLR on x86-64
in 4.8-rc1 AFAICS and this should make them work together again.

Unless anyone sees any problems with it, I'll queue it up for 4.8-rc2.

Thomas, would it be possible to test it with KASLR enabled, please?

I tested it on my setup couple times. Worked well.

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Is that the only patch which needs to be tested? Ontop of which tree?

That should be the only one on top of plain 4.8-rc1.

If it doesn't help, we need more work to do. :-)

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CONFIG_RANDOMIZE_MEMORY blew up s2d on my laptop here so I'll run it
once I have the required info from you :)

Thanks!

Best,
Rafael