linux-kernel - [PATCH V2 02/30] mm/mmap: Clarify protection

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Date:   Mon, 21 Feb 2022 12:08:11 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-mm@...ck.org, akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org,
        Anshuman Khandual <anshuman.khandual@....com>,
        Christoph Hellwig <hch@...radead.org>,
        linux-arch@...r.kernel.org
Subject: [PATCH V2 02/30] mm/mmap: Clarify protection_map[] indices

protection_map[] maps vm_flags access combinations into page protection
value as defined by the platform via __PXXX and __SXXX macros. The array
indices in protection_map[], represents vm_flags access combinations but
it's not very intuitive to derive. This makes it clear and explicit.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 mm/mmap.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 1e8fdb0b51ed..670c68f5fbf1 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -102,8 +102,22 @@ static void unmap_region(struct mm_struct *mm,
  *								x: (yes) yes
  */
 pgprot_t protection_map[16] __ro_after_init = {
-	__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
-	__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
+	[VM_NONE]					= __P000,
+	[VM_READ]					= __P001,
+	[VM_WRITE]					= __P010,
+	[VM_WRITE | VM_READ]				= __P011,
+	[VM_EXEC]					= __P100,
+	[VM_EXEC | VM_READ]				= __P101,
+	[VM_EXEC | VM_WRITE]				= __P110,
+	[VM_EXEC | VM_WRITE | VM_READ]			= __P111,
+	[VM_SHARED]					= __S000,
+	[VM_SHARED | VM_READ]				= __S001,
+	[VM_SHARED | VM_WRITE]				= __S010,
+	[VM_SHARED | VM_WRITE | VM_READ]		= __S011,
+	[VM_SHARED | VM_EXEC]				= __S100,
+	[VM_SHARED | VM_EXEC | VM_READ]			= __S101,
+	[VM_SHARED | VM_EXEC | VM_WRITE]		= __S110,
+	[VM_SHARED | VM_EXEC | VM_WRITE | VM_READ]	= __S111
 };
 
 #ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
-- 
2.25.1