[PATCH v20 4/7] mm: introduce memfd_secret system call to create "secret" memory areas

[Andrew Morton]

On Tue, 18 May 2021 10:20:31 +0300 Mike Rapoport <rppt at kernel.org> 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.
> 
> ...
>
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -901,4 +901,9 @@ config KMAP_LOCAL
>  # struct io_mapping based helper.  Selected by drivers that need them
>  config IO_MAPPING
>  	bool
> +
> +config SECRETMEM
> +	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
> +	select STRICT_DEVMEM
> +
>  endmenu

WARNING: unmet direct dependencies detected for STRICT_DEVMEM
  Depends on [n]: MMU [=y] && DEVMEM [=n] && (ARCH_HAS_DEVMEM_IS_ALLOWED [=y] || GENERIC_LIB_DEVMEM_IS_ALLOWED [=n])
  Selected by [y]:
  - SECRETMEM [=y]

so I went back to the v19 version, with

--- a/mm/Kconfig~mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix
+++ a/mm/Kconfig
@@ -907,6 +907,5 @@ config IO_MAPPING
 
 config SECRETMEM
 	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
-	select STRICT_DEVMEM
 
 endmenu
_