On Sat, Feb 18, 2023 at 01:14:05PM -0800, Rick Edgecombe wrote:

The x86 Control-flow Enforcement Technology (CET) feature includes a new
type of memory called shadow stack. This shadow stack memory has some
unusual properties, which requires some core mm changes to function
properly.

One of these unusual properties is that shadow stack memory is writable,
but only in limited ways. These limits are applied via a specific PTE
bit combination. Nevertheless, the memory is writable, and core mm code
will need to apply the writable permissions in the typical paths that
call pte_mkwrite().

In addition to VM_WRITE, the shadow stack VMA's will have a flag denoting
that they are special shadow stack flavor of writable memory. So make
pte_mkwrite() take a VMA, so that the x86 implementation of it can know to
create regular writable memory or shadow stack memory.

Apply the same changes for pmd_mkwrite() and huge_pte_mkwrite().

No functional change.

Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
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Cc: Michal Simek <monstr@monstr.eu>
Cc: Dinh Nguyen <dinguyen@kernel.org>
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Tested-by: Pengfei Xu <redacted>
Suggested-by: David Hildenbrand <redacted>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>

Acked-by: Deepak Gupta <redacted>