linux-kernel - [PATCH V2 01/30] mm/debug_vm_pgtable: Drop protection

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Message-Id: <1645425519-9034-2-git-send-email-anshuman.khandual@arm.com>
Date:   Mon, 21 Feb 2022 12:08:10 +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 01/30] mm/debug_vm_pgtable: Drop protection_map[] usage

Although protection_map[] contains the platform defined page protection map
for a given vm_flags combination, vm_get_page_prot() is the right interface
to use. This will also reduce dependency on protection_map[] which is going
to be dropped off completely later on.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 mm/debug_vm_pgtable.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index db2abd9e415b..30fd11a2ed32 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -93,7 +93,7 @@ struct pgtable_debug_args {
 
 static void __init pte_basic_tests(struct pgtable_debug_args *args, int idx)
 {
-	pgprot_t prot = protection_map[idx];
+	pgprot_t prot = vm_get_page_prot(idx);
 	pte_t pte = pfn_pte(args->fixed_pte_pfn, prot);
 	unsigned long val = idx, *ptr = &val;
 
@@ -101,7 +101,7 @@ static void __init pte_basic_tests(struct pgtable_debug_args *args, int idx)
 
 	/*
 	 * This test needs to be executed after the given page table entry
-	 * is created with pfn_pte() to make sure that protection_map[idx]
+	 * is created with pfn_pte() to make sure that vm_get_page_prot(idx)
 	 * does not have the dirty bit enabled from the beginning. This is
 	 * important for platforms like arm64 where (!PTE_RDONLY) indicate
 	 * dirty bit being set.
@@ -190,7 +190,7 @@ static void __init pte_savedwrite_tests(struct pgtable_debug_args *args)
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx)
 {
-	pgprot_t prot = protection_map[idx];
+	pgprot_t prot = vm_get_page_prot(idx);
 	unsigned long val = idx, *ptr = &val;
 	pmd_t pmd;
 
@@ -202,7 +202,7 @@ static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx)
 
 	/*
 	 * This test needs to be executed after the given page table entry
-	 * is created with pfn_pmd() to make sure that protection_map[idx]
+	 * is created with pfn_pmd() to make sure that vm_get_page_prot(idx)
 	 * does not have the dirty bit enabled from the beginning. This is
 	 * important for platforms like arm64 where (!PTE_RDONLY) indicate
 	 * dirty bit being set.
@@ -325,7 +325,7 @@ static void __init pmd_savedwrite_tests(struct pgtable_debug_args *args)
 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx)
 {
-	pgprot_t prot = protection_map[idx];
+	pgprot_t prot = vm_get_page_prot(idx);
 	unsigned long val = idx, *ptr = &val;
 	pud_t pud;
 
@@ -337,7 +337,7 @@ static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx)
 
 	/*
 	 * This test needs to be executed after the given page table entry
-	 * is created with pfn_pud() to make sure that protection_map[idx]
+	 * is created with pfn_pud() to make sure that vm_get_page_prot(idx)
 	 * does not have the dirty bit enabled from the beginning. This is
 	 * important for platforms like arm64 where (!PTE_RDONLY) indicate
 	 * dirty bit being set.
@@ -1106,14 +1106,14 @@ static int __init init_args(struct pgtable_debug_args *args)
 	/*
 	 * Initialize the debugging data.
 	 *
-	 * protection_map[0] (or even protection_map[8]) will help create
-	 * page table entries with PROT_NONE permission as required for
-	 * pxx_protnone_tests().
+	 * vm_get_page_prot(VM_NONE) or vm_get_page_prot(VM_SHARED|VM_NONE)
+	 * will help create page table entries with PROT_NONE permission as
+	 * required for pxx_protnone_tests().
 	 */
 	memset(args, 0, sizeof(*args));
 	args->vaddr              = get_random_vaddr();
 	args->page_prot          = vm_get_page_prot(VMFLAGS);
-	args->page_prot_none     = protection_map[0];
+	args->page_prot_none     = vm_get_page_prot(VM_NONE);
 	args->is_contiguous_page = false;
 	args->pud_pfn            = ULONG_MAX;
 	args->pmd_pfn            = ULONG_MAX;
@@ -1248,12 +1248,19 @@ static int __init debug_vm_pgtable(void)
 		return ret;
 
 	/*
-	 * Iterate over the protection_map[] to make sure that all
+	 * Iterate over each possible vm_flags to make sure that all
 	 * the basic page table transformation validations just hold
 	 * true irrespective of the starting protection value for a
 	 * given page table entry.
+	 *
+	 * Protection based vm_flags combinatins are always linear
+	 * and increasing i.e starting from VM_NONE and going upto
+	 * (VM_SHARED | READ | WRITE | EXEC).
 	 */
-	for (idx = 0; idx < ARRAY_SIZE(protection_map); idx++) {
+#define VM_FLAGS_START	(VM_NONE)
+#define VM_FLAGS_END	(VM_SHARED | VM_EXEC | VM_WRITE | VM_READ)
+
+	for (idx = VM_FLAGS_START; idx <= VM_FLAGS_END; idx++) {
 		pte_basic_tests(&args, idx);
 		pmd_basic_tests(&args, idx);
 		pud_basic_tests(&args, idx);
-- 
2.25.1