Hi Michael,

Thanks for all the comments!  I'll fix most of it when I post a new
version of the manpage, but I have a few general questions.

On 12/09/2015 03:08 AM, Michael Kerrisk (man-pages) wrote:

quoted

+is the protection or storage key to assign to the memory.

Why "protection or storage key" here? This phrasing seems a
little ambiguous to me, given that we also have a 'prot'
argument.  I think it would be clearer just to say 
"protection key". But maybe I'm missing something.

x86 calls it a "protection key" while powerpc calls it a "storage key".
 They're called "protection keys" consistently inside the kernel.

Should we just stick to one name in the manpages?

* A general overview of why this functionality is useful.

Any preference on a central spot to do the general overview?  Does it go
in one of the manpages I'm already modifying, or a new one?

* A note on which architectures support/will support
  this functionality.

x86 only for now.  We might get powerpc support down the road somewhere.

* Explanation of what a protection domain is.

A protection domain is a unique view of memory and is represented by the
value in the PKRU register.

* Explanation of how a process (thread?) changes its
  protection domain.

Changing protection domains is done by pkey_set() system call, or by
using the WRPKRU instruction.  The system call is preferred and less
error-prone since it enforces that a protection is allocated before its
access protection can be modified.

* Explanation of the relationship between page permission
  bits (PROT_READ/PROT_WRITE/PROTE_EXEC) and 
  PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE.
  It's still not clear to me. Do the PKEY_* bits
  override the PROT_* bits. Or, something else?

Protection keys add access restrictions in addition to existing page
permissions.  They can only take away access; they never grant
additional access.

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