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[ARM] pgtable: file pte layout documentation 

Document the layout of our file PTE entries.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2009-07-05 11:52:21 +01:00 committed by Russell King
parent fb93a1c75e
commit 65b1bfc13e
1 changed files with 14 additions and 9 deletions
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23
arch/arm/include/asm/pgtable.h
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@ -285,15 +285,6 @@ extern struct page *empty_zero_page;
#define pte_young(pte) (pte_val(pte) & L_PTE_YOUNG)
#define pte_special(pte) (0)
/*
* The following only works if pte_present() is not true.
*/
#define pte_file(pte) (pte_val(pte) & L_PTE_FILE)
#define pte_to_pgoff(x) (pte_val(x) >> 2)
#define pgoff_to_pte(x) __pte(((x) << 2) | L_PTE_FILE)
#define PTE_FILE_MAX_BITS 30
#define PTE_BIT_FUNC(fn,op) \
static inline pte_t pte_##fn(pte_t pte) { pte_val(pte) op; return pte; }
@ -414,6 +405,20 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
*/
#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > __SWP_TYPE_BITS)
/*
* Encode and decode a file entry. File entries are stored in the Linux
* page tables as follows:
*
* 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
* 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
* <------------------------ offset -------------------------> 1 0
*/
#define pte_file(pte) (pte_val(pte) & L_PTE_FILE)
#define pte_to_pgoff(x) (pte_val(x) >> 2)
#define pgoff_to_pte(x) __pte(((x) << 2) | L_PTE_FILE)
#define PTE_FILE_MAX_BITS 30
/* Needs to be defined here and not in linux/mm.h, as it is arch dependent */
/* FIXME: this is not correct */
#define kern_addr_valid(addr) (1)