[PATCH V3 01/30] mm/debug_vm_pgtable: Drop protection_map[] usage

Anshuman Khandual
2022-02-28T10:49:02Z

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@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.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