linux-kernel - [PATCH 4/6] UML - Fix pte bit collision

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Message-ID: <20070327182749.GA8411@c2.user-mode-linux.org>
Date:	Tue, 27 Mar 2007 14:27:49 -0400
From:	Jeff Dike <jdike@...toit.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	Miklos Szeredi <mszeredi@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>,
	uml-devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: [PATCH 4/6] UML - Fix pte bit collision

From: Miklos Szeredi <mszeredi@...e.cz>

_PAGE_PROTNONE conflicts with the lowest bit of pgoff.  This causes
all sorts of weirdness when nonlinear mappings are used.

Took me a good half day to track this down.

Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
Signed-off-by: Jeff Dike <jdike@...ux.intel.com>
--
 include/asm-um/pgtable-2level.h |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Index: linux-2.6.21-mm/include/asm-um/pgtable-2level.h
===================================================================
--- linux-2.6.21-mm.orig/include/asm-um/pgtable-2level.h	2007-03-27 12:34:31.000000000 -0400
+++ linux-2.6.21-mm/include/asm-um/pgtable-2level.h	2007-03-27 12:52:12.000000000 -0400
@@ -45,12 +45,12 @@ static inline void pgd_mkuptodate(pgd_t 
 	((unsigned long) __va(pmd_val(pmd) & PAGE_MASK))
 
 /*
- * Bits 0 through 3 are taken
+ * Bits 0 through 4 are taken
  */
-#define PTE_FILE_MAX_BITS	28
+#define PTE_FILE_MAX_BITS	27
 
-#define pte_to_pgoff(pte) (pte_val(pte) >> 4)
+#define pte_to_pgoff(pte) (pte_val(pte) >> 5)
 
-#define pgoff_to_pte(off) ((pte_t) { ((off) << 4) + _PAGE_FILE })
+#define pgoff_to_pte(off) ((pte_t) { ((off) << 5) + _PAGE_FILE })
 
 #endif
-
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