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/*
* linux/arch/arm/mm/minicache.c
*
* Copyright (C) 2001 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This handles the mini data cache, as found on SA11x0 and XScale
* processors. When we copy a user page page, we map it in such a way
* that accesses to this page will not touch the main data cache, but
* will be cached in the mini data cache. This prevents us thrashing
* the main data cache on page faults.
*/
#include <linux/init.h>
#include <linux/mm.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
/*
* 0xffff8000 to 0xffffffff is reserved for any ARM architecture
* specific hacks for copying pages efficiently.
*/
#define minicache_address (0xffff8000)
#define minicache_pgprot __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | \
L_PTE_CACHEABLE)
static pte_t *minicache_pte;
/*
* Note that this is intended to be called only from the copy_user_page
* asm code; anything else will require special locking to prevent the
* mini-cache space being re-used. (Note: probably preempt unsafe).
*
* We rely on the fact that the minicache is 2K, and we'll be pushing
* 4K of data through it, so we don't actually have to specifically
* flush the minicache when we change the mapping.
*
* Note also: assert(PAGE_OFFSET <= virt < high_memory).
* Unsafe: preempt, kmap.
*/
unsigned long map_page_minicache(unsigned long virt)
{
set_pte(minicache_pte, pfn_pte(__pa(virt) >> PAGE_SHIFT, minicache_pgprot));
flush_tlb_kernel_page(minicache_address);
return minicache_address;
}
static int __init minicache_init(void)
{
pgd_t *pgd;
pmd_t *pmd;
spin_lock(&init_mm.page_table_lock);
pgd = pgd_offset_k(minicache_address);
pmd = pmd_alloc(&init_mm, pgd, minicache_address);
if (!pmd)
BUG();
minicache_pte = pte_alloc_kernel(&init_mm, pmd, minicache_address);
if (!minicache_pte)
BUG();
spin_unlock(&init_mm.page_table_lock);
return 0;
}
core_initcall(minicache_init);
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