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PAGE_ALIGN(): correctly handle 64-bit values on 32-bit architectures

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On 32-bit architectures PAGE_ALIGN() truncates 64-bit values to the 32-bit
boundary. For example:

	u64 val = PAGE_ALIGN(size);

always returns a value < 4GB even if size is greater than 4GB.

The problem resides in PAGE_MASK definition (from include/asm-x86/page.h for
example):

#define PAGE_SHIFT      12
#define PAGE_SIZE       (_AC(1,UL) << PAGE_SHIFT)
#define PAGE_MASK       (~(PAGE_SIZE-1))
...
#define PAGE_ALIGN(addr)       (((addr)+PAGE_SIZE-1)&PAGE_MASK)

The "~" is performed on a 32-bit value, so everything in "and" with
PAGE_MASK greater than 4GB will be truncated to the 32-bit boundary.
Using the ALIGN() macro seems to be the right way, because it uses
typeof(addr) for the mask.

Also move the PAGE_ALIGN() definitions out of include/asm-*/page.h in
include/linux/mm.h.

See also lkml discussion: http://lkml.org/lkml/2008/6/11/237

[[email protected]: fix drivers/media/video/uvc/uvc_queue.c]
[[email protected]: fix v850]
[[email protected]: fix powerpc]
[[email protected]: fix arm]
[[email protected]: fix mips]
[[email protected]: fix drivers/media/video/pvrusb2/pvrusb2-dvb.c]
[[email protected]: fix drivers/mtd/maps/uclinux.c]
[[email protected]: fix powerpc]
Signed-off-by: Andrea Righi <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Andrea Righi 2008-07-23 21:28:13 -07:00 • committed by Linus Torvalds
commit 27ac792ca0
57 changed files with 36 additions and 74 deletions
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3
include/asm-mips/page.h
View file

@ -137,9 +137,6 @@ typedef struct { unsigned long pgprot; } pgprot_t;
#endif /* !__ASSEMBLY__ */
/* to align the pointer to the (next) page boundary */
#define PAGE_ALIGN(addr) (((addr) + PAGE_SIZE - 1) & PAGE_MASK)
/*
* __pa()/__va() should be used only during mem init.
*/

2
include/asm-mips/processor.h
View file

@ -45,7 +45,7 @@ extern unsigned int vced_count, vcei_count;
* This decides where the kernel will search for a free chunk of vm
* space during mmap's.
*/
#define TASK_UNMAPPED_BASE (PAGE_ALIGN(TASK_SIZE / 3))
#define TASK_UNMAPPED_BASE ((TASK_SIZE / 3) & ~(PAGE_SIZE))
#endif
#ifdef CONFIG_64BIT