/*
* linux/arch/arm/mm/fault-armv.c
*
* Copyright (C) 1995 Linus Torvalds
* Modifications for ARM processor (c) 1995-2002 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.
*/
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/bitops.h>
#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <asm/cacheflush.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
static unsigned long shared_pte_mask = L_PTE_CACHEABLE;
/*
* We take the easy way out of this problem - we make the
* PTE uncacheable. However, we leave the write buffer on.
*
* Note that the pte lock held when calling update_mmu_cache must also
* guard the pte (somewhere else in the same mm) that we modify here.
* Therefore those configurations which might call adjust_pte (those
* without CONFIG_CPU_CACHE_VIPT) cannot support split page_table_lock.
*/
static int adjust_pte(struct vm_area_struct *vma, unsigned long address)
{
pgd_t *pgd;
pmd_t *pmd;
pte_t *pte, entry;
int ret;
pgd = pgd_offset(vma->vm_mm, address);
if (pgd_none(*pgd))
goto no_pgd;
if (pgd_bad(*pgd))
goto bad_pgd;
pmd = pmd_offset(pgd, address);
if (pmd_none(*pmd))
goto no_pmd;
if (pmd_bad(*pmd))
goto bad_pmd;
pte = pte_offset_map(pmd, address);
entry = *pte;
/*
* If this page is present, it's actually being shared.
*/
ret = pte_present(entry);
/*
* If this page isn't present, or is already setup to
* fault (ie, is old), we can safely ignore any issues.
*/
if (ret && pte_val(entry) & shared_pte_mask) {
flush_cache_page(vma, address, pte_pfn(entry));
pte_val(entry) &= ~shared_pte_mask;
set_pte_at(vma->vm_mm, address, pte, entry);
flush_tlb_page(vma, address);
}
pte_unmap(pte);
return ret;
bad_pgd:
pgd_ERROR(*pgd);
pgd_clear(pgd);
no_pgd:
return 0;
bad_pmd:
pmd_ERROR(*pmd);
pmd_clear(pmd);
no_pmd:
return 0;
}
static void
make_coherent(struct address_space *mapping, struct vm_area_struct *vma, unsigned long addr, unsigned long pfn)
{
struct mm_struct *mm = vma->vm_mm;
struct vm_area_struct *mpnt;
struct prio_tree_iter iter;
unsigned long offset;
pgoff_t pgoff;
int aliases = 0;
pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT);
/*
* If we have any shared mappings that are in the same mm
* space, then we need to handle them specially to maintain
* cache coherency.
*/
flush_dcache_mmap_lock(mapping);
vma_prio_tree_foreach(mpnt, &iter, &mapping->i_mmap, pgoff, pgoff) {
/*
* If this VMA is not in our MM, we can ignore it.
* Note that we intentionally mask out the VMA
* that we are fixing up.
*/
if (mpnt->vm_mm != mm || mpnt == vma)
continue;
if (!(mpnt->vm_flags & VM_MAYSHARE))
continue;
offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
aliases += adjust_pte(mpnt, mpnt->vm_start + offset);
}
flush_dcache_mmap_unlock(mapping);
if (aliases)
adjust_pte(vma, addr);
else
flush_cache_page(vma, addr, pfn);
}
/*
* Take care of architecture specific things when placing a new PTE into
* a page table, or changing an existing PTE. Basically, there are two
* things that we need to take care of:
*
* 1. If PG_dcache_dirty is set for the page, we need to ensure
* that any cache entries for the kernels virtual memory
* range are written back to the page.
* 2. If we have multiple shared mappings of the same space in
* an object, we need to deal with the cache aliasing issues.
*
* Note that the pte lock will be held.
*/
void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
{
unsigned long pfn = pte_pfn(pte);
struct address_space *mapping;
struct page *page;
if (!pfn_valid(pfn))
return;
page = pfn_to_page(pfn);
mapping = page_mapping(page);
if (mapping) {
#ifndef CONFIG_SMP
int dirty = test_and_clear_bit(PG_dcache_dirty, &page->flags);
if (dirty)
__flush_dcache_page(mapping, page);
#endif
if (cache_is_vivt())
make_coherent(mapping, vma, addr, pfn);
else if (vma->vm_flags & VM_EXEC)
__flush_icache_all();
}
}
/*
* Check whether the write buffer has physical address aliasing
* issues. If it has, we need to avoid them for the case where
* we have several shared mappings of the same object in user
* space.
*/
static int __init check_writebuffer(unsigned long *p1, unsigned long *p2)
{
register unsigned long zero = 0, one = 1, val;
local_irq_disable();
mb();
*p1 = one;
mb();
*p2 = zero;
mb();
val = *p1;
mb();
local_irq_enable();
return val != zero;
}
void __init check_writebuffer_bugs(void)
{
struct page *page;
const char *reason;
unsigned long v = 1;
printk(KERN_INFO "CPU: Testing write buffer coherency: ");
page = alloc_page(GFP_KERNEL);
if (page) {
unsigned long *p1, *p2;
pgprot_t prot = __pgprot(L_PTE_PRESENT|L_PTE_YOUNG|
L_PTE_DIRTY|L_PTE_WRITE|
L_PTE_BUFFERABLE);
p1 = vmap(&page, 1, VM_IOREMAP, prot);
p2 = vmap(&page, 1, VM_IOREMAP, prot);
if (p1 && p2) {
v = check_writebuffer(p1, p2);
reason = "enabling work-around";
} else {
reason = "unable to map memory\n";
}
vunmap(p1);
vunmap(p2);
put_page(page);
} else {
reason = "unable to grab page\n";
}
if (v) {
printk("failed, %s\n", reason);
shared_pte_mask |= L_PTE_BUFFERABLE;
} else {
printk("ok\n");
}
}
