[PATCH] ARM: VM: fix user page protection values (was Re: [PATCH] DEV: zero: use correct pgprot for zeromapping)

Imre Deak
2007-02-10T17:30:10Z

On Sat, Feb 10, 2007 at 12:03:40PM +0200, Imre Deak wrote:
> On Sat, Feb 10, 2007 at 09:39:54AM +0000, Russell King wrote:
> > On Sat, Feb 10, 2007 at 11:15:21AM +0200, Imre Deak wrote:
> > > Instead of PAGE_COPY use the pgprot bits established already at
> > > original mapping time of the VMA. This will also include any
> > > architecture specific bits setup through protection_map.
> > > zeromap_page_range will take care of COW'ing the passed pgprot.
> >
> > NAK. What if PAGE_COPY is used elsewhere and ends up accidentally
> > allowing write access?
>
> Or rather, result in the bogus global mapping. True.
>
> >
> > I think the right solution is to make PAGE_COPY a variable in the same
> > way that PAGE_KERNEL is, and adjust it as appropriate.
>
> Ok, and also at least PAGE_SHARED and PAGE_READONLY I assume.

[ For consistency base all PAGE_* macros off a variable. I tested this
on ARM1136. ]

The PAGE_* user page protection macros don't take into account the
configured memory policy and other architecture specific bits like
the global/ASID and shared mapping bits. Instead of constants let
these depend on a variable fixed up at init just like PAGE_KERNEL.

Signed-off-by: Imre Deak <imre.deak@solidboot.com>
---
arch/arm/mm/mmu.c | 3 ++
include/asm-arm/pgtable.h | 54 ++++++++++++++++++++++++++------------------
2 files changed, 35 insertions(+), 22 deletions(-)

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 655c837..94fd4bf 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -49,8 +49,10 @@ pmd_t *top_pmd;

static unsigned int cachepolicy __initdata = CPOLICY_WRITEBACK;
static unsigned int ecc_mask __initdata = 0;
+pgprot_t pgprot_user;
pgprot_t pgprot_kernel;

+EXPORT_SYMBOL(pgprot_user);
EXPORT_SYMBOL(pgprot_kernel);

struct cachepolicy {
@@ -345,6 +347,7 @@ static void __init build_mem_type_table(void)
mem_types[MT_MINICLEAN].prot_sect &= ~PMD_SECT_TEX(1);
}

+ pgprot_user = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | user_pgprot);
pgprot_kernel = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG |
L_PTE_DIRTY | L_PTE_WRITE |
L_PTE_EXEC | kern_pgprot);
diff --git a/include/asm-arm/pgtable.h b/include/asm-arm/pgtable.h
index b8cf2d5..7b2bafc 100644
--- a/include/asm-arm/pgtable.h
+++ b/include/asm-arm/pgtable.h
@@ -175,19 +175,29 @@ extern void __pgd_error(const char *file, int line, unsigned long val);
#ifndef __ASSEMBLY__

/*
- * The following macros handle the cache and bufferable bits...
+ * The pgprot_* and protection_map entries will be fixed up in runtime
+ * to include the cachable and bufferable bits based on memory policy,
+ * as well as any architecture dependent bits like global/ASID and SMP
+ * shared mapping bits.
*/
#define _L_PTE_DEFAULT L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_CACHEABLE | L_PTE_BUFFERABLE
#define _L_PTE_READ L_PTE_USER | L_PTE_EXEC

+extern pgprot_t pgprot_user;
extern pgprot_t pgprot_kernel;

-#define PAGE_NONE __pgprot(_L_PTE_DEFAULT)
-#define PAGE_COPY __pgprot(_L_PTE_DEFAULT | _L_PTE_READ)
-#define PAGE_SHARED __pgprot(_L_PTE_DEFAULT | _L_PTE_READ | L_PTE_WRITE)
-#define PAGE_READONLY __pgprot(_L_PTE_DEFAULT | _L_PTE_READ)
+#define PAGE_NONE pgprot_user
+#define PAGE_COPY __pgprot(pgprot_val(pgprot_user) | _L_PTE_READ)
+#define PAGE_SHARED __pgprot(pgprot_val(pgprot_user) | _L_PTE_READ | \
+ L_PTE_WRITE)
+#define PAGE_READONLY __pgprot(pgprot_val(pgprot_user) | _L_PTE_READ)
#define PAGE_KERNEL pgprot_kernel

+#define __PAGE_NONE __pgprot(_L_PTE_DEFAULT)
+#define __PAGE_COPY __pgprot(_L_PTE_DEFAULT | _L_PTE_READ)
+#define __PAGE_SHARED __pgprot(_L_PTE_DEFAULT | _L_PTE_READ | L_PTE_WRITE)
+#define __PAGE_READONLY __pgprot(_L_PTE_DEFAULT | _L_PTE_READ)
+
#endif /* __ASSEMBLY__ */

/*
@@ -198,23 +208,23 @@ extern pgprot_t pgprot_kernel;
* 2) If we could do execute protection, then read is implied
* 3) write implies read permissions
*/
-#define __P000 PAGE_NONE
-#define __P001 PAGE_READONLY
-#define __P010 PAGE_COPY
-#define __P011 PAGE_COPY
-#define __P100 PAGE_READONLY
-#define __P101 PAGE_READONLY
-#define __P110 PAGE_COPY
-#define __P111 PAGE_COPY
-
-#define __S000 PAGE_NONE
-#define __S001 PAGE_READONLY
-#define __S010 PAGE_SHARED
-#define __S011 PAGE_SHARED
-#define __S100 PAGE_READONLY
-#define __S101 PAGE_READONLY
-#define __S110 PAGE_SHARED
-#define __S111 PAGE_SHARED
+#define __P000 __PAGE_NONE
+#define __P001 __PAGE_READONLY
+#define __P010 __PAGE_COPY
+#define __P011 __PAGE_COPY
+#define __P100 __PAGE_READONLY
+#define __P101 __PAGE_READONLY
+#define __P110 __PAGE_COPY
+#define __P111 __PAGE_COPY
+
+#define __S000 __PAGE_NONE
+#define __S001 __PAGE_READONLY
+#define __S010 __PAGE_SHARED
+#define __S011 __PAGE_SHARED
+#define __S100 __PAGE_READONLY
+#define __S101 __PAGE_READONLY
+#define __S110 __PAGE_SHARED
+#define __S111 __PAGE_SHARED

#ifndef __ASSEMBLY__
/*
--
1.4.4.3.GIT