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copypage-v4mc.c

/*
 *  linux/arch/arm/lib/copypage-armv4mc.S
 *
 *  Copyright (C) 1995-2005 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 <linux/highmem.h>

#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/cacheflush.h>

#include "mm.h"

/*
 * 0xffff8000 to 0xffffffff is reserved for any ARM architecture
 * specific hacks for copying pages efficiently.
 */
#define minicache_pgprot __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | \
                          L_PTE_MT_MINICACHE)

static DEFINE_SPINLOCK(minicache_lock);

/*
 * ARMv4 mini-dcache optimised copy_user_highpage
 *
 * We flush the destination cache lines just before we write the data into the
 * corresponding address.  Since the Dcache is read-allocate, this removes the
 * Dcache aliasing issue.  The writes will be forwarded to the write buffer,
 * and merged as appropriate.
 *
 * Note: We rely on all ARMv4 processors implementing the "invalidate D line"
 * instruction.  If your processor does not supply this, you have to write your
 * own copy_user_highpage that does the right thing.
 */
static void __naked
mc_copy_user_page(void *from, void *to)
{
      asm volatile(
      "stmfd      sp!, {r4, lr}                 @ 2\n\
      mov   r4, %2                        @ 1\n\
      ldmia %0!, {r2, r3, ip, lr}         @ 4\n\
1:    mcr   p15, 0, %1, c7, c6, 1         @ 1   invalidate D line\n\
      stmia %1!, {r2, r3, ip, lr}         @ 4\n\
      ldmia %0!, {r2, r3, ip, lr}         @ 4+1\n\
      stmia %1!, {r2, r3, ip, lr}         @ 4\n\
      ldmia %0!, {r2, r3, ip, lr}         @ 4\n\
      mcr   p15, 0, %1, c7, c6, 1         @ 1   invalidate D line\n\
      stmia %1!, {r2, r3, ip, lr}         @ 4\n\
      ldmia %0!, {r2, r3, ip, lr}         @ 4\n\
      subs  r4, r4, #1              @ 1\n\
      stmia %1!, {r2, r3, ip, lr}         @ 4\n\
      ldmneia     %0!, {r2, r3, ip, lr}         @ 4\n\
      bne   1b                      @ 1\n\
      ldmfd sp!, {r4, pc}                 @ 3"
      :
      : "r" (from), "r" (to), "I" (PAGE_SIZE / 64));
}

void v4_mc_copy_user_highpage(struct page *to, struct page *from,
      unsigned long vaddr, struct vm_area_struct *vma)
{
      void *kto = kmap_atomic(to, KM_USER1);

      if (!test_and_set_bit(PG_dcache_clean, &from->flags))
            __flush_dcache_page(page_mapping(from), from);

      spin_lock(&minicache_lock);

      set_pte_ext(TOP_PTE(0xffff8000), pfn_pte(page_to_pfn(from), minicache_pgprot), 0);
      flush_tlb_kernel_page(0xffff8000);

      mc_copy_user_page((void *)0xffff8000, kto);

      spin_unlock(&minicache_lock);

      kunmap_atomic(kto, KM_USER1);
}

/*
 * ARMv4 optimised clear_user_page
 */
void v4_mc_clear_user_highpage(struct page *page, unsigned long vaddr)
{
      void *ptr, *kaddr = kmap_atomic(page, KM_USER0);
      asm volatile("\
      mov   r1, %2                        @ 1\n\
      mov   r2, #0                        @ 1\n\
      mov   r3, #0                        @ 1\n\
      mov   ip, #0                        @ 1\n\
      mov   lr, #0                        @ 1\n\
1:    mcr   p15, 0, %0, c7, c6, 1         @ 1   invalidate D line\n\
      stmia %0!, {r2, r3, ip, lr}         @ 4\n\
      stmia %0!, {r2, r3, ip, lr}         @ 4\n\
      mcr   p15, 0, %0, c7, c6, 1         @ 1   invalidate D line\n\
      stmia %0!, {r2, r3, ip, lr}         @ 4\n\
      stmia %0!, {r2, r3, ip, lr}         @ 4\n\
      subs  r1, r1, #1              @ 1\n\
      bne   1b                      @ 1"
      : "=r" (ptr)
      : "0" (kaddr), "I" (PAGE_SIZE / 64)
      : "r1", "r2", "r3", "ip", "lr");
      kunmap_atomic(kaddr, KM_USER0);
}

struct cpu_user_fns v4_mc_user_fns __initdata = {
      .cpu_clear_user_highpage = v4_mc_clear_user_highpage,
      .cpu_copy_user_highpage = v4_mc_copy_user_highpage,
};

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