linux-kernel - [RFC V1 03/31] mm/mmap: Add new config ARCH_HAS_VM_GET_PAGE

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Message-Id: <1643029028-12710-4-git-send-email-anshuman.khandual@arm.com>
Date:   Mon, 24 Jan 2022 18:26:40 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, hch@...radead.org,
        akpm@...ux-foundation.org,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: [RFC V1 03/31] mm/mmap: Add new config ARCH_HAS_VM_GET_PAGE_PROT

Add a new config ARCH_HAS_VM_GET_PAGE_PROT, which when subscribed enables a
given platform to define its own vm_get_page_prot(). This framework will
help remove protection_map[] dependency going forward.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
Suggested-by: Christoph Hellwig <hch@...radead.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 mm/Kconfig | 3 +++
 mm/mmap.c  | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/mm/Kconfig b/mm/Kconfig
index 257ed9c86de3..fa436478a94c 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -747,6 +747,9 @@ config ARCH_HAS_CACHE_LINE_SIZE
 config ARCH_HAS_FILTER_PGPROT
 	bool
 
+config ARCH_HAS_VM_GET_PAGE_PROT
+	bool
+
 config ARCH_HAS_PTE_DEVMAP
 	bool
 
diff --git a/mm/mmap.c b/mm/mmap.c
index 254d716220df..ec403de32dcb 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -81,6 +81,7 @@ static void unmap_region(struct mm_struct *mm,
 		struct vm_area_struct *vma, struct vm_area_struct *prev,
 		unsigned long start, unsigned long end);
 
+#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
 /* description of effects of mapping type and prot in current implementation.
  * this is due to the limited x86 page protection hardware.  The expected
  * behavior is in parens:
@@ -136,6 +137,7 @@ pgprot_t vm_get_page_prot(unsigned long vm_flags)
 	return arch_filter_pgprot(ret);
 }
 EXPORT_SYMBOL(vm_get_page_prot);
+#endif	/* CONFIG_ARCH_HAS_VM_GET_PAGE_PROT */
 
 static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
 {
-- 
2.25.1