[RFC V1 05/31] arm64/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

[RFC V1 05/31] arm64/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

[Anshuman Khandual]

This defines and exports a platform specific custom vm_get_page_prot() via
subscribing ARCH_HAS_VM_GET_PAGE_PROT. Subsequently all __SXXX and __PXXX
macros can be dropped which are no longer needed. This also localizes both
arch_filter_pgprot and arch_vm_get_page_prot() helpers, unsubscribing from
ARCH_HAS_FILTER_PGPROT as well.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/arm64/Kconfig                    |  2 +-
 arch/arm64/include/asm/mman.h         |  3 +-
 arch/arm64/include/asm/pgtable-prot.h | 18 ----------
 arch/arm64/include/asm/pgtable.h      |  2 +-
 arch/arm64/mm/mmap.c                  | 50 +++++++++++++++++++++++++++
 5 files changed, 53 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index cad609528e58..fce2d0fc4ecc 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -23,7 +23,6 @@ config ARM64
 	select ARCH_HAS_DMA_PREP_COHERENT
 	select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
 	select ARCH_HAS_FAST_MULTIPLIER
-	select ARCH_HAS_FILTER_PGPROT
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_GIGANTIC_PAGE
@@ -44,6 +43,7 @@ config ARM64
 	select ARCH_HAS_SYSCALL_WRAPPER
 	select ARCH_HAS_TEARDOWN_DMA_OPS if IOMMU_SUPPORT
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
+	select ARCH_HAS_VM_GET_PAGE_PROT
 	select ARCH_HAS_ZONE_DMA_SET if EXPERT
 	select ARCH_HAVE_ELF_PROT
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
index e3e28f7daf62..85f41f72a8b3 100644
--- a/arch/arm64/include/asm/mman.h
+++ b/arch/arm64/include/asm/mman.h
@@ -35,7 +35,7 @@ static inline unsigned long arch_calc_vm_flag_bits(unsigned long flags)
 }
 #define arch_calc_vm_flag_bits(flags) arch_calc_vm_flag_bits(flags)
 
-static inline pgprot_t arch_vm_get_page_prot(unsigned long vm_flags)
+static inline pgprot_t arm64_arch_vm_get_page_prot(unsigned long vm_flags)
 {
 	pteval_t prot = 0;
 
@@ -57,7 +57,6 @@ static inline pgprot_t arch_vm_get_page_prot(unsigned long vm_flags)
 
 	return __pgprot(prot);
 }
-#define arch_vm_get_page_prot(vm_flags) arch_vm_get_page_prot(vm_flags)
 
 static inline bool arch_validate_prot(unsigned long prot,
 	unsigned long addr __always_unused)
diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index 7032f04c8ac6..d8ee0aa7886d 100644
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -88,24 +88,6 @@ extern bool arm64_use_ng_mappings;
 #define PAGE_READONLY_EXEC	__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN)
 #define PAGE_EXECONLY		__pgprot(_PAGE_DEFAULT | PTE_RDONLY | PTE_NG | PTE_PXN)
 
-#define __P000  PAGE_NONE
-#define __P001  PAGE_READONLY
-#define __P010  PAGE_READONLY
-#define __P011  PAGE_READONLY
-#define __P100  PAGE_EXECONLY
-#define __P101  PAGE_READONLY_EXEC
-#define __P110  PAGE_READONLY_EXEC
-#define __P111  PAGE_READONLY_EXEC
-
-#define __S000  PAGE_NONE
-#define __S001  PAGE_READONLY
-#define __S010  PAGE_SHARED
-#define __S011  PAGE_SHARED
-#define __S100  PAGE_EXECONLY
-#define __S101  PAGE_READONLY_EXEC
-#define __S110  PAGE_SHARED_EXEC
-#define __S111  PAGE_SHARED_EXEC
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* __ASM_PGTABLE_PROT_H */
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index c4ba047a82d2..5a73501a45ed 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1017,7 +1017,7 @@ static inline bool arch_wants_old_prefaulted_pte(void)
 }
 #define arch_wants_old_prefaulted_pte	arch_wants_old_prefaulted_pte
 
-static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
+static inline pgprot_t arm64_arch_filter_pgprot(pgprot_t prot)
 {
 	if (cpus_have_const_cap(ARM64_HAS_EPAN))
 		return prot;
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index a38f54cd638c..ad605eb86d23 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -10,6 +10,7 @@
 #include <linux/types.h>
 
 #include <asm/page.h>
+#include <asm/mman.h>
 
 /*
  * You really shouldn't be using read() or write() on /dev/mem.  This might go
@@ -38,3 +39,52 @@ int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
 {
 	return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK);
 }
+
+static inline pgprot_t __vm_get_page_prot(unsigned long vm_flags)
+{
+	switch (vm_flags & (VM_READ | VM_WRITE | VM_EXEC | VM_SHARED)) {
+	case VM_NONE:
+		return PAGE_NONE;
+	case VM_READ:
+		return PAGE_READONLY;
+	case VM_WRITE:
+		return PAGE_READONLY;
+	case VM_READ | VM_WRITE:
+		return PAGE_READONLY;
+	case VM_EXEC:
+		return PAGE_EXECONLY;
+	case VM_EXEC | VM_READ:
+		return PAGE_READONLY_EXEC;
+	case VM_EXEC | VM_WRITE:
+		return PAGE_READONLY_EXEC;
+	case VM_EXEC | VM_READ | VM_WRITE:
+		return PAGE_READONLY_EXEC;
+	case VM_SHARED:
+		return PAGE_NONE;
+	case VM_SHARED | VM_READ:
+		return PAGE_READONLY;
+	case VM_SHARED | VM_WRITE:
+		return PAGE_SHARED;
+	case VM_SHARED | VM_READ | VM_WRITE:
+		return PAGE_SHARED;
+	case VM_SHARED | VM_EXEC:
+		return PAGE_EXECONLY;
+	case VM_SHARED | VM_EXEC | VM_READ:
+		return PAGE_READONLY_EXEC;
+	case VM_SHARED | VM_EXEC | VM_WRITE:
+		return PAGE_SHARED_EXEC;
+	case VM_SHARED | VM_EXEC | VM_READ | VM_WRITE:
+		return PAGE_SHARED_EXEC;
+	default:
+		BUILD_BUG();
+	}
+}
+
+pgprot_t vm_get_page_prot(unsigned long vm_flags)
+{
+	pgprot_t ret = __pgprot(pgprot_val(__vm_get_page_prot(vm_flags)) |
+			pgprot_val(arm64_arch_vm_get_page_prot(vm_flags)));
+
+	return arm64_arch_filter_pgprot(ret);
+}
+EXPORT_SYMBOL(vm_get_page_prot);
-- 
2.25.1


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[RFC V1 09/31] arm/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

[Anshuman Khandual]

This defines and exports a platform specific custom vm_get_page_prot() via
subscribing ARCH_HAS_VM_GET_PAGE_PROT. Subsequently all __SXXX and __PXXX
macros can be dropped which are no longer needed.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/arm/Kconfig               |  1 +
 arch/arm/include/asm/pgtable.h | 18 ------------
 arch/arm/mm/mmu.c              | 50 ++++++++++++++++++++++++++++++----
 3 files changed, 45 insertions(+), 24 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index fabe39169b12..c12362d20c44 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -23,6 +23,7 @@ config ARM
 	select ARCH_HAS_SYNC_DMA_FOR_CPU if SWIOTLB || !MMU
 	select ARCH_HAS_TEARDOWN_DMA_OPS if MMU
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
+	select ARCH_HAS_VM_GET_PAGE_PROT
 	select ARCH_HAVE_CUSTOM_GPIO_H
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG if CPU_V7 || CPU_V7M || CPU_V6K
 	select ARCH_HAS_GCOV_PROFILE_ALL
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index cd1f84bb40ae..ec062dd6082a 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -137,24 +137,6 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
  *  2) If we could do execute protection, then read is implied
  *  3) write implies read permissions
  */
-#define __P000  __PAGE_NONE
-#define __P001  __PAGE_READONLY
-#define __P010  __PAGE_COPY
-#define __P011  __PAGE_COPY
-#define __P100  __PAGE_READONLY_EXEC
-#define __P101  __PAGE_READONLY_EXEC
-#define __P110  __PAGE_COPY_EXEC
-#define __P111  __PAGE_COPY_EXEC
-
-#define __S000  __PAGE_NONE
-#define __S001  __PAGE_READONLY
-#define __S010  __PAGE_SHARED
-#define __S011  __PAGE_SHARED
-#define __S100  __PAGE_READONLY_EXEC
-#define __S101  __PAGE_READONLY_EXEC
-#define __S110  __PAGE_SHARED_EXEC
-#define __S111  __PAGE_SHARED_EXEC
-
 #ifndef __ASSEMBLY__
 /*
  * ZERO_PAGE is a global shared page that is always zero: used
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 274e4f73fd33..3007d07bc0e7 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -403,6 +403,8 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
 	local_flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
 }
 
+static pteval_t user_pgprot;
+
 /*
  * Adjust the PMD section entries according to the CPU in use.
  */
@@ -410,7 +412,7 @@ static void __init build_mem_type_table(void)
 {
 	struct cachepolicy *cp;
 	unsigned int cr = get_cr();
-	pteval_t user_pgprot, kern_pgprot, vecs_pgprot;
+	pteval_t kern_pgprot, vecs_pgprot;
 	int cpu_arch = cpu_architecture();
 	int i;
 
@@ -627,11 +629,6 @@ static void __init build_mem_type_table(void)
 	user_pgprot |= PTE_EXT_PXN;
 #endif
 
-	for (i = 0; i < 16; i++) {
-		pteval_t v = pgprot_val(protection_map[i]);
-		protection_map[i] = __pgprot(v | user_pgprot);
-	}
-
 	mem_types[MT_LOW_VECTORS].prot_pte |= vecs_pgprot;
 	mem_types[MT_HIGH_VECTORS].prot_pte |= vecs_pgprot;
 
@@ -670,6 +667,47 @@ static void __init build_mem_type_table(void)
 	}
 }
 
+pgprot_t vm_get_page_prot(unsigned long vm_flags)
+{
+	switch (vm_flags & (VM_READ | VM_WRITE | VM_EXEC | VM_SHARED)) {
+	case VM_NONE:
+		return __pgprot(pgprot_val(__PAGE_NONE) | user_pgprot);
+	case VM_READ:
+		return __pgprot(pgprot_val(__PAGE_READONLY) | user_pgprot);
+	case VM_WRITE:
+		return __pgprot(pgprot_val(__PAGE_COPY) | user_pgprot);
+	case VM_READ | VM_WRITE:
+		return __pgprot(pgprot_val(__PAGE_COPY) | user_pgprot);
+	case VM_EXEC:
+		return __pgprot(pgprot_val(__PAGE_READONLY_EXEC) | user_pgprot);
+	case VM_EXEC | VM_READ:
+		return __pgprot(pgprot_val(__PAGE_READONLY_EXEC) | user_pgprot);
+	case VM_EXEC | VM_WRITE:
+		return __pgprot(pgprot_val(__PAGE_COPY_EXEC) | user_pgprot);
+	case VM_EXEC | VM_READ | VM_WRITE:
+		return __pgprot(pgprot_val(__PAGE_COPY_EXEC) | user_pgprot);
+	case VM_SHARED:
+		return __pgprot(pgprot_val(__PAGE_NONE) | user_pgprot);
+	case VM_SHARED | VM_READ:
+		return __pgprot(pgprot_val(__PAGE_READONLY) | user_pgprot);
+	case VM_SHARED | VM_WRITE:
+		return __pgprot(pgprot_val(__PAGE_SHARED) | user_pgprot);
+	case VM_SHARED | VM_READ | VM_WRITE:
+		return __pgprot(pgprot_val(__PAGE_SHARED) | user_pgprot);
+	case VM_SHARED | VM_EXEC:
+		return __pgprot(pgprot_val(__PAGE_READONLY_EXEC) | user_pgprot);
+	case VM_SHARED | VM_EXEC | VM_READ:
+		return __pgprot(pgprot_val(__PAGE_READONLY_EXEC) | user_pgprot);
+	case VM_SHARED | VM_EXEC | VM_WRITE:
+		return __pgprot(pgprot_val(__PAGE_SHARED_EXEC) | user_pgprot);
+	case VM_SHARED | VM_EXEC | VM_READ | VM_WRITE:
+		return __pgprot(pgprot_val(__PAGE_SHARED_EXEC) | user_pgprot);
+	default:
+		BUILD_BUG();
+	}
+}
+EXPORT_SYMBOL(vm_get_page_prot);
+
 #ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 			      unsigned long size, pgprot_t vma_prot)
-- 
2.25.1


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Re: [RFC V1 09/31] arm/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

[Russell King (Oracle)]

On Mon, Jan 24, 2022 at 06:26:46PM +0530, Anshuman Khandual wrote:
> This defines and exports a platform specific custom vm_get_page_prot() via
> subscribing ARCH_HAS_VM_GET_PAGE_PROT. Subsequently all __SXXX and __PXXX
> macros can be dropped which are no longer needed.

What is the fundamental advantage of this approach?

> 
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
>  arch/arm/Kconfig               |  1 +
>  arch/arm/include/asm/pgtable.h | 18 ------------
>  arch/arm/mm/mmu.c              | 50 ++++++++++++++++++++++++++++++----
>  3 files changed, 45 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index fabe39169b12..c12362d20c44 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -23,6 +23,7 @@ config ARM
>  	select ARCH_HAS_SYNC_DMA_FOR_CPU if SWIOTLB || !MMU
>  	select ARCH_HAS_TEARDOWN_DMA_OPS if MMU
>  	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> +	select ARCH_HAS_VM_GET_PAGE_PROT
>  	select ARCH_HAVE_CUSTOM_GPIO_H
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG if CPU_V7 || CPU_V7M || CPU_V6K
>  	select ARCH_HAS_GCOV_PROFILE_ALL
> diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
> index cd1f84bb40ae..ec062dd6082a 100644
> --- a/arch/arm/include/asm/pgtable.h
> +++ b/arch/arm/include/asm/pgtable.h
> @@ -137,24 +137,6 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>   *  2) If we could do execute protection, then read is implied
>   *  3) write implies read permissions
>   */
> -#define __P000  __PAGE_NONE
> -#define __P001  __PAGE_READONLY
> -#define __P010  __PAGE_COPY
> -#define __P011  __PAGE_COPY
> -#define __P100  __PAGE_READONLY_EXEC
> -#define __P101  __PAGE_READONLY_EXEC
> -#define __P110  __PAGE_COPY_EXEC
> -#define __P111  __PAGE_COPY_EXEC
> -
> -#define __S000  __PAGE_NONE
> -#define __S001  __PAGE_READONLY
> -#define __S010  __PAGE_SHARED
> -#define __S011  __PAGE_SHARED
> -#define __S100  __PAGE_READONLY_EXEC
> -#define __S101  __PAGE_READONLY_EXEC
> -#define __S110  __PAGE_SHARED_EXEC
> -#define __S111  __PAGE_SHARED_EXEC
> -
>  #ifndef __ASSEMBLY__
>  /*
>   * ZERO_PAGE is a global shared page that is always zero: used
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index 274e4f73fd33..3007d07bc0e7 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -403,6 +403,8 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
>  	local_flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
>  }
>  
> +static pteval_t user_pgprot;
> +
>  /*
>   * Adjust the PMD section entries according to the CPU in use.
>   */
> @@ -410,7 +412,7 @@ static void __init build_mem_type_table(void)
>  {
>  	struct cachepolicy *cp;
>  	unsigned int cr = get_cr();
> -	pteval_t user_pgprot, kern_pgprot, vecs_pgprot;
> +	pteval_t kern_pgprot, vecs_pgprot;
>  	int cpu_arch = cpu_architecture();
>  	int i;
>  
> @@ -627,11 +629,6 @@ static void __init build_mem_type_table(void)
>  	user_pgprot |= PTE_EXT_PXN;
>  #endif
>  
> -	for (i = 0; i < 16; i++) {
> -		pteval_t v = pgprot_val(protection_map[i]);
> -		protection_map[i] = __pgprot(v | user_pgprot);
> -	}
> -
>  	mem_types[MT_LOW_VECTORS].prot_pte |= vecs_pgprot;
>  	mem_types[MT_HIGH_VECTORS].prot_pte |= vecs_pgprot;
>  
> @@ -670,6 +667,47 @@ static void __init build_mem_type_table(void)
>  	}
>  }
>  
> +pgprot_t vm_get_page_prot(unsigned long vm_flags)
> +{
> +	switch (vm_flags & (VM_READ | VM_WRITE | VM_EXEC | VM_SHARED)) {
> +	case VM_NONE:
> +		return __pgprot(pgprot_val(__PAGE_NONE) | user_pgprot);
> +	case VM_READ:
> +		return __pgprot(pgprot_val(__PAGE_READONLY) | user_pgprot);
> +	case VM_WRITE:
> +		return __pgprot(pgprot_val(__PAGE_COPY) | user_pgprot);
> +	case VM_READ | VM_WRITE:
> +		return __pgprot(pgprot_val(__PAGE_COPY) | user_pgprot);
> +	case VM_EXEC:
> +		return __pgprot(pgprot_val(__PAGE_READONLY_EXEC) | user_pgprot);
> +	case VM_EXEC | VM_READ:
> +		return __pgprot(pgprot_val(__PAGE_READONLY_EXEC) | user_pgprot);
> +	case VM_EXEC | VM_WRITE:
> +		return __pgprot(pgprot_val(__PAGE_COPY_EXEC) | user_pgprot);
> +	case VM_EXEC | VM_READ | VM_WRITE:
> +		return __pgprot(pgprot_val(__PAGE_COPY_EXEC) | user_pgprot);
> +	case VM_SHARED:
> +		return __pgprot(pgprot_val(__PAGE_NONE) | user_pgprot);
> +	case VM_SHARED | VM_READ:
> +		return __pgprot(pgprot_val(__PAGE_READONLY) | user_pgprot);
> +	case VM_SHARED | VM_WRITE:
> +		return __pgprot(pgprot_val(__PAGE_SHARED) | user_pgprot);
> +	case VM_SHARED | VM_READ | VM_WRITE:
> +		return __pgprot(pgprot_val(__PAGE_SHARED) | user_pgprot);
> +	case VM_SHARED | VM_EXEC:
> +		return __pgprot(pgprot_val(__PAGE_READONLY_EXEC) | user_pgprot);
> +	case VM_SHARED | VM_EXEC | VM_READ:
> +		return __pgprot(pgprot_val(__PAGE_READONLY_EXEC) | user_pgprot);
> +	case VM_SHARED | VM_EXEC | VM_WRITE:
> +		return __pgprot(pgprot_val(__PAGE_SHARED_EXEC) | user_pgprot);
> +	case VM_SHARED | VM_EXEC | VM_READ | VM_WRITE:
> +		return __pgprot(pgprot_val(__PAGE_SHARED_EXEC) | user_pgprot);
> +	default:
> +		BUILD_BUG();
> +	}
> +}
> +EXPORT_SYMBOL(vm_get_page_prot);
> +
>  #ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE
>  pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>  			      unsigned long size, pgprot_t vma_prot)
> -- 
> 2.25.1
> 
> 

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Re: [RFC V1 09/31] arm/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

[Anshuman Khandual]

On 1/24/22 10:36 PM, Russell King (Oracle) wrote:
> On Mon, Jan 24, 2022 at 06:26:46PM +0530, Anshuman Khandual wrote:
>> This defines and exports a platform specific custom vm_get_page_prot() via
>> subscribing ARCH_HAS_VM_GET_PAGE_PROT. Subsequently all __SXXX and __PXXX
>> macros can be dropped which are no longer needed.
>
> What is the fundamental advantage of this approach?
> 

Remove multiple 'core MM <--> platform' abstraction layers to map
vm_flags access permission combination into page protection. From
the cover letter ..

----------
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 all these abstraction levels and instead
just move the responsibility of defining vm_get_page_prot() to the platform
itself making it clean and simple.
----------


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