[PATCH v3 3/6] mm: introduce memfd_secret system call to create "secret" memory areas

Kirill A. Shutemov kirill at shutemov.name
Thu Aug 6 06:27:57 EDT 2020

On Tue, Aug 04, 2020 at 12:50:32PM +0300, Mike Rapoport wrote:
> From: Mike Rapoport <rppt at linux.ibm.com>
> Introduce "memfd_secret" system call with the ability to create memory
> areas visible only in the context of the owning process and not mapped not
> only to other processes but in the kernel page tables as well.
> The user will create a file descriptor using the memfd_secret() system call
> where flags supplied as a parameter to this system call will define the
> desired protection mode for the memory associated with that file
> descriptor. Currently there are two protection modes:
> * exclusive - the memory area is unmapped from the kernel direct map and it
>               is present only in the page tables of the owning mm.
> * uncached  - the memory area is present only in the page tables of the
>               owning mm and it is mapped there as uncached.

I'm not sure why flag for exclusive mode is needed. It has to be default.
And if you want uncached on top of that set the flag.
What am I missing?

 Kirill A. Shutemov

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