[PATCH V4 0/7] mm/mmap: Drop arch_vm_get_page_prot() and arch_filter_pgprot()

Anshuman Khandual
2022-04-07T10:34:21Z

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@arm.com/

This series applies on 5.18-rc1 after the following patch.

https://lore.kernel.org/all/1643004823-16441-1-git-send-email-anshuman.khandual@arm.com/

This series has been cross built for multiple platforms.

- Anshuman

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: sparclinux@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Changes in V4:

- 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@arm.com/

- 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@arm.com/

- 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@arm.com/

- 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@arm.com/

Changes in RFC:

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

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 | 33 ++++++++++++++++++++++++++++++
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/mman.h | 12 -----------
arch/powerpc/mm/mmap.c | 26 ++++++++++++++++++++++++
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 | 14 ++++---------
17 files changed, 117 insertions(+), 78 deletions(-)
create mode 100644 arch/x86/mm/pgprot.c

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2.25.1