On Wed, Oct 29, 2025 at 9:08 PM Maciej Wieczor-Retman
[off-list ref] wrote:

From: Maciej Wieczor-Retman <redacted>

To make use of KASAN's tag based mode on x86, Linear Address Masking
(LAM) needs to be enabled. To do that the 28th bit in CR4 has to be set.

Set the bit in early memory initialization.

When launching secondary CPUs the LAM bit gets lost. To avoid this add
it in a mask in head_64.S. The bitmask permits some bits of CR4 to pass
from the primary CPU to the secondary CPUs without being cleared.

Signed-off-by: Maciej Wieczor-Retman <redacted>

Acked-by: Alexander Potapenko <glider@google.com>