[PATCH V6 0/7] mm/mmap: Drop arch_vm_get_page_prot() and arch_filter_pgprot()

[Anshuman Khandual]

protection_map[] is an array based construct that translates given vm_flags
combination. This array contains page protection map, which is populated by
the platform via [__S000 .. __S111] and [__P000 .. __P111] exported macros.
Primary usage for protection_map[] is for vm_get_page_prot(), which is used
to determine page protection value for a given vm_flags. vm_get_page_prot()
implementation, could again call platform overrides arch_vm_get_page_prot()
and arch_filter_pgprot(). Some platforms override protection_map[] that was
originally built with __SXXX/__PXXX with different runtime values.

Currently there are multiple layers of abstraction i.e __SXXX/__PXXX macros
, protection_map[], arch_vm_get_page_prot() and arch_filter_pgprot() built
between the platform and generic MM, finally defining vm_get_page_prot().

Hence this series proposes to drop later two abstraction levels and instead
just move the responsibility of defining vm_get_page_prot() to the platform
(still utilizing generic protection_map[] array) itself making it clean and
simple.

This first introduces ARCH_HAS_VM_GET_PAGE_PROT which enables the platforms
to define custom vm_get_page_prot(). This starts converting platforms that
define the overrides arch_filter_pgprot() or arch_vm_get_page_prot() which
enables for those constructs to be dropped off completely.

The series has been inspired from an earlier discuss with Christoph Hellwig

https://lore.kernel.org/all/1632712920-8171-1-git-send-email-anshuman.khandual@xxxxxxx/

This series applies on 5.18-rc2.

This series has been cross built for multiple platforms.

- Anshuman

Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: sparclinux@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

Changes in V6:

- Created single merged vm_get_page_prot() function per Christophe
- Dropped local variable 'ret' in generic vm_get_page_prot() per Christophe
- Dropped __pgprot(pgprot_val(x)) in generic vm_get_page_prot() per Christophe

Changes in V5:

https://lore.kernel.org/all/20220412043848.80464-2-anshuman.khandual@xxxxxxx/

- Collected new tags on various patches in the series
- Coalesced arm64_arch_vm_get_page_prot() into vm_get_page_prot() per Catalin
- Modified powerpc's vm_get_page_prot() implementation per Christophe

Changes in V4:

https://lore.kernel.org/all/20220407103251.1209606-1-anshuman.khandual@xxxxxxx/

- ARCH_HAS_VM_GET_PAGE_PROT now excludes generic protection_map[]
- Changed platform's vm_get_page_prot() to use generic protection_map[]
- Dropped all platform changes not enabling either arch_vm_get_page_prot() or arch_filter_pgprot() 
- Dropped all previous tags as code base has changed

Changes in V3:

https://lore.kernel.org/all/1646045273-9343-1-git-send-email-anshuman.khandual@xxxxxxx/

- Dropped variable 'i' from sme_early_init() on x86 platform
- Moved CONFIG_COLDFIRE vm_get_page_prot() inside arch/m68k/mm/mcfmmu.c
- Moved CONFIG_SUN3 vm_get_page_prot() inside arch/m68k/mm/sun3mmu.c
- Dropped cachebits for vm_get_page_prot() inside arch/m68k/mm/motorola.c
- Dropped PAGE_XXX_C definitions from arch/m68k/include/asm/motorola_pgtable.h
- Used PAGE_XXX instead for vm_get_page_prot() inside arch/m68k/mm/motorola.c
- Dropped all references to protection_map[] in the tree
- Replaced s/extensa/xtensa/ on the patch title
- Moved left over comments from pgtable.h into init.c on nios2 platform

Changes in V2:

https://lore.kernel.org/all/1645425519-9034-1-git-send-email-anshuman.khandual@xxxxxxx/

- Dropped the entire comment block in [PATCH 30/30] per Geert
- Replaced __P010 (although commented) with __PAGE_COPY on arm platform
- Replaced __P101 with PAGE_READONLY on um platform

Changes in V1:

https://lore.kernel.org/all/1644805853-21338-1-git-send-email-anshuman.khandual@xxxxxxx/

- Add white spaces around the | operators 
- Moved powerpc_vm_get_page_prot() near vm_get_page_prot() on powerpc
- Moved arm64_vm_get_page_prot() near vm_get_page_prot() on arm64
- Moved sparc_vm_get_page_prot() near vm_get_page_prot() on sparc
- Compacted vm_get_page_prot() switch cases on all platforms
-  _PAGE_CACHE040 inclusion is dependent on CPU_IS_040_OR_060
- VM_SHARED case should return PAGE_NONE (not PAGE_COPY) on SH platform
- Reorganized VM_SHARED, VM_EXEC, VM_WRITE, VM_READ
- Dropped the last patch [RFC V1 31/31] which added macros for vm_flags combinations
  https://lore.kernel.org/all/1643029028-12710-32-git-send-email-anshuman.khandual@xxxxxxx/

Changes in RFC:

https://lore.kernel.org/all/1643029028-12710-1-git-send-email-anshuman.khandual@xxxxxxx/


Anshuman Khandual (6):
  mm/mmap: Add new config ARCH_HAS_VM_GET_PAGE_PROT
  powerpc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
  arm64/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
  sparc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT
  mm/mmap: Drop arch_filter_pgprot()
  mm/mmap: Drop arch_vm_get_page_pgprot()

Christoph Hellwig (1):
  x86/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

 arch/arm64/Kconfig                 |  1 +
 arch/arm64/include/asm/mman.h      | 24 --------------------
 arch/arm64/mm/mmap.c               | 25 +++++++++++++++++++++
 arch/powerpc/Kconfig               |  1 +
 arch/powerpc/include/asm/mman.h    | 12 ----------
 arch/powerpc/mm/book3s64/pgtable.c | 17 +++++++++++++++
 arch/sparc/Kconfig                 |  1 +
 arch/sparc/include/asm/mman.h      |  6 -----
 arch/sparc/mm/init_64.c            | 13 +++++++++++
 arch/x86/Kconfig                   |  2 +-
 arch/x86/include/asm/pgtable.h     |  5 -----
 arch/x86/include/uapi/asm/mman.h   | 14 ------------
 arch/x86/mm/Makefile               |  2 +-
 arch/x86/mm/pgprot.c               | 35 ++++++++++++++++++++++++++++++
 include/linux/mman.h               |  4 ----
 mm/Kconfig                         |  2 +-
 mm/mmap.c                          | 15 +++----------
 17 files changed, 99 insertions(+), 80 deletions(-)
 create mode 100644 arch/x86/mm/pgprot.c

-- 
2.25.1