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Index > Heap > New instructions RDPKRU/WRPKRU

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Joined: 04 Sep 2009
Posts: 308
Location: film "CandyMan" directed through Bernard Rose OR Candy Shop
Memory Protection Keys for Userspace (PKU aka PKEYs) is a CPU
feature which will be found in future Intel CPUs. The work here
was done with the aid of simulators.

Memory Protection Keys provides a mechanism for enforcing
page-based protections, but without requiring modification of the
page tables when an application changes protection domains. It
works by dedicating 4 previously ignored bits in each page table
entry to a "protection key", giving 16 possible keys.

There is also a new user-accessible register (PKRU) with two
separate bits (Access Disable and Write Disable) for each key.
Being a CPU register, PKRU is inherently thread-local,
potentially giving each thread a different set of protections
from every other thread.

There are two new instructions (RDPKRU/WRPKRU) for reading and
writing to the new register. The feature is only available in
64-bit mode, even though there is theoretically space in the PAE
PTEs. These permissions are enforced on data access only and
have no effect on instruction fetches.

smaller is better
Post 13 Mar 2016, 17:59
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