[PATCH V3 1/2] mm/mmap: Restrict generic protection_map[] array visibility

From: Anshuman Khandual
Date: Thu Jun 16 2022 - 00:09:45 EST

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Restrict generic protection_map[] array visibility only for platforms which
do not enable ARCH_HAS_VM_GET_PAGE_PROT. For other platforms that do define
their own vm_get_page_prot() enabling ARCH_HAS_VM_GET_PAGE_PROT, could have
their private static protection_map[] still implementing an array look up.
These private protection_map[] array could do without __PXXX/__SXXX macros,
making them redundant and dropping them off as well.

But platforms which do not define their custom vm_get_page_prot() enabling
ARCH_HAS_VM_GET_PAGE_PROT, will still have to provide __PXXX/__SXXX macros.

Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Acked-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
arch/arm64/include/asm/pgtable-prot.h | 18 ------------------
arch/arm64/mm/mmap.c | 21 +++++++++++++++++++++
arch/powerpc/include/asm/pgtable.h | 2 ++
arch/powerpc/mm/book3s64/pgtable.c | 20 ++++++++++++++++++++
arch/sparc/include/asm/pgtable_64.h | 19 -------------------
arch/sparc/mm/init_64.c | 3 +++
arch/x86/include/asm/pgtable_types.h | 19 -------------------
arch/x86/mm/pgprot.c | 19 +++++++++++++++++++
include/linux/mm.h | 2 ++
mm/mmap.c | 2 +-
10 files changed, 68 insertions(+), 57 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index 62e0ebeed720..9b165117a454 100644
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -89,24 +89,6 @@ 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_READONLY_EXEC /* PAGE_EXECONLY if Enhanced PAN */
-#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_READONLY_EXEC /* PAGE_EXECONLY if Enhanced PAN */
-#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/mm/mmap.c b/arch/arm64/mm/mmap.c
index 78e9490f748d..8f5b7ce857ed 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -13,6 +13,27 @@
#include <asm/cpufeature.h>
#include <asm/page.h>

+static pgprot_t protection_map[16] __ro_after_init = {
+ [VM_NONE] = PAGE_NONE,
+ [VM_READ] = PAGE_READONLY,
+ [VM_WRITE] = PAGE_READONLY,
+ [VM_WRITE | VM_READ] = PAGE_READONLY,
+ /* PAGE_EXECONLY if Enhanced PAN */
+ [VM_EXEC] = PAGE_READONLY_EXEC,
+ [VM_EXEC | VM_READ] = PAGE_READONLY_EXEC,
+ [VM_EXEC | VM_WRITE] = PAGE_READONLY_EXEC,
+ [VM_EXEC | VM_WRITE | VM_READ] = PAGE_READONLY_EXEC,
+ [VM_SHARED] = PAGE_NONE,
+ [VM_SHARED | VM_READ] = PAGE_READONLY,
+ [VM_SHARED | VM_WRITE] = PAGE_SHARED,
+ [VM_SHARED | VM_WRITE | VM_READ] = PAGE_SHARED,
+ /* PAGE_EXECONLY if Enhanced PAN */
+ [VM_SHARED | VM_EXEC] = PAGE_READONLY_EXEC,
+ [VM_SHARED | VM_EXEC | VM_READ] = PAGE_READONLY_EXEC,
+ [VM_SHARED | VM_EXEC | VM_WRITE] = PAGE_SHARED_EXEC,
+ [VM_SHARED | VM_EXEC | VM_WRITE | VM_READ] = PAGE_SHARED_EXEC
+};
+
/*
* You really shouldn't be using read() or write() on /dev/mem. This might go
* away in the future.
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index d564d0ecd4cd..8ed2a80c896e 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -21,6 +21,7 @@ struct mm_struct;
#endif /* !CONFIG_PPC_BOOK3S */

/* Note due to the way vm flags are laid out, the bits are XWR */
+#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
#define __P000 PAGE_NONE
#define __P001 PAGE_READONLY
#define __P010 PAGE_COPY
@@ -38,6 +39,7 @@ struct mm_struct;
#define __S101 PAGE_READONLY_X
#define __S110 PAGE_SHARED_X
#define __S111 PAGE_SHARED_X
+#endif

#ifndef __ASSEMBLY__

diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
index 7b9966402b25..d3b019b95c1d 100644
--- a/arch/powerpc/mm/book3s64/pgtable.c
+++ b/arch/powerpc/mm/book3s64/pgtable.c
@@ -551,6 +551,26 @@ unsigned long memremap_compat_align(void)
EXPORT_SYMBOL_GPL(memremap_compat_align);
#endif

+/* Note due to the way vm flags are laid out, the bits are XWR */
+static const pgprot_t protection_map[16] = {
+ [VM_NONE] = PAGE_NONE,
+ [VM_READ] = PAGE_READONLY,
+ [VM_WRITE] = PAGE_COPY,
+ [VM_WRITE | VM_READ] = PAGE_COPY,
+ [VM_EXEC] = PAGE_READONLY_X,
+ [VM_EXEC | VM_READ] = PAGE_READONLY_X,
+ [VM_EXEC | VM_WRITE] = PAGE_COPY_X,
+ [VM_EXEC | VM_WRITE | VM_READ] = PAGE_COPY_X,
+ [VM_SHARED] = PAGE_NONE,
+ [VM_SHARED | VM_READ] = PAGE_READONLY,
+ [VM_SHARED | VM_WRITE] = PAGE_SHARED,
+ [VM_SHARED | VM_WRITE | VM_READ] = PAGE_SHARED,
+ [VM_SHARED | VM_EXEC] = PAGE_READONLY_X,
+ [VM_SHARED | VM_EXEC | VM_READ] = PAGE_READONLY_X,
+ [VM_SHARED | VM_EXEC | VM_WRITE] = PAGE_SHARED_X,
+ [VM_SHARED | VM_EXEC | VM_WRITE | VM_READ] = PAGE_SHARED_X
+};
+
pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
unsigned long prot = pgprot_val(protection_map[vm_flags &
diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 4679e45c8348..a779418ceba9 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -187,25 +187,6 @@ bool kern_addr_valid(unsigned long addr);
#define _PAGE_SZHUGE_4U _PAGE_SZ4MB_4U
#define _PAGE_SZHUGE_4V _PAGE_SZ4MB_4V

-/* These are actually filled in at boot time by sun4{u,v}_pgprot_init() */
-#define __P000 __pgprot(0)
-#define __P001 __pgprot(0)
-#define __P010 __pgprot(0)
-#define __P011 __pgprot(0)
-#define __P100 __pgprot(0)
-#define __P101 __pgprot(0)
-#define __P110 __pgprot(0)
-#define __P111 __pgprot(0)
-
-#define __S000 __pgprot(0)
-#define __S001 __pgprot(0)
-#define __S010 __pgprot(0)
-#define __S011 __pgprot(0)
-#define __S100 __pgprot(0)
-#define __S101 __pgprot(0)
-#define __S110 __pgprot(0)
-#define __S111 __pgprot(0)
-
#ifndef __ASSEMBLY__

pte_t mk_pte_io(unsigned long, pgprot_t, int, unsigned long);
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index f6174df2d5af..d6faee23c77d 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -2634,6 +2634,9 @@ void vmemmap_free(unsigned long start, unsigned long end,
}
#endif /* CONFIG_SPARSEMEM_VMEMMAP */

+/* These are actually filled in at boot time by sun4{u,v}_pgprot_init() */
+static pgprot_t protection_map[16] __ro_after_init;
+
static void prot_init_common(unsigned long page_none,
unsigned long page_shared,
unsigned long page_copy,
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index bdaf8391e2e0..aa174fed3a71 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -230,25 +230,6 @@ enum page_cache_mode {

#endif /* __ASSEMBLY__ */

-/* xwr */
-#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
-
/*
* early identity mapping pte attrib macros.
*/
diff --git a/arch/x86/mm/pgprot.c b/arch/x86/mm/pgprot.c
index 763742782286..7eca1b009af6 100644
--- a/arch/x86/mm/pgprot.c
+++ b/arch/x86/mm/pgprot.c
@@ -4,6 +4,25 @@
#include <linux/mm.h>
#include <asm/pgtable.h>

+static pgprot_t protection_map[16] __ro_after_init = {
+ [VM_NONE] = PAGE_NONE,
+ [VM_READ] = PAGE_READONLY,
+ [VM_WRITE] = PAGE_COPY,
+ [VM_WRITE | VM_READ] = PAGE_COPY,
+ [VM_EXEC] = PAGE_READONLY_EXEC,
+ [VM_EXEC | VM_READ] = PAGE_READONLY_EXEC,
+ [VM_EXEC | VM_WRITE] = PAGE_COPY_EXEC,
+ [VM_EXEC | VM_WRITE | VM_READ] = PAGE_COPY_EXEC,
+ [VM_SHARED] = PAGE_NONE,
+ [VM_SHARED | VM_READ] = PAGE_READONLY,
+ [VM_SHARED | VM_WRITE] = PAGE_SHARED,
+ [VM_SHARED | VM_WRITE | VM_READ] = PAGE_SHARED,
+ [VM_SHARED | VM_EXEC] = PAGE_READONLY_EXEC,
+ [VM_SHARED | VM_EXEC | VM_READ] = PAGE_READONLY_EXEC,
+ [VM_SHARED | VM_EXEC | VM_WRITE] = PAGE_SHARED_EXEC,
+ [VM_SHARED | VM_EXEC | VM_WRITE | VM_READ] = PAGE_SHARED_EXEC
+};
+
pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
unsigned long val = pgprot_val(protection_map[vm_flags &
diff --git a/include/linux/mm.h b/include/linux/mm.h
index bc8f326be0ce..2254c1980c8e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -420,11 +420,13 @@ extern unsigned int kobjsize(const void *objp);
#endif
#define VM_FLAGS_CLEAR (ARCH_VM_PKEY_FLAGS | VM_ARCH_CLEAR)

+#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
/*
* mapping from the currently active vm_flags protection bits (the
* low four bits) to a page protection mask..
*/
extern pgprot_t protection_map[16];
+#endif

/*
* The default fault flags that should be used by most of the
diff --git a/mm/mmap.c b/mm/mmap.c
index 61e6135c54ef..e66920414945 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -101,6 +101,7 @@ static void unmap_region(struct mm_struct *mm,
* w: (no) no
* x: (yes) yes
*/
+#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
pgprot_t protection_map[16] __ro_after_init = {
[VM_NONE] = __P000,
[VM_READ] = __P001,
@@ -120,7 +121,6 @@ pgprot_t protection_map[16] __ro_after_init = {
[VM_SHARED | VM_EXEC | VM_WRITE | VM_READ] = __S111
};

-#ifndef CONFIG_ARCH_HAS_VM_GET_PAGE_PROT
pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
return protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
--
2.25.1

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