339 lines
9.0 KiB
C
339 lines
9.0 KiB
C
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/*
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* This file contains common routines for dealing with free of page tables
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* Along with common page table handling code
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*
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* Derived from arch/powerpc/mm/tlb_64.c:
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* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
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*
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* Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
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* and Cort Dougan (PReP) (cort@cs.nmt.edu)
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* Copyright (C) 1996 Paul Mackerras
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*
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* Derived from "arch/i386/mm/init.c"
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*
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* Dave Engebretsen <engebret@us.ibm.com>
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* Rework for PPC64 port.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/init.h>
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#include <linux/percpu.h>
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#include <linux/hardirq.h>
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#include <asm/pgalloc.h>
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#include <asm/tlbflush.h>
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#include <asm/tlb.h>
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#include "mmu_decl.h"
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DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
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#ifdef CONFIG_SMP
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/*
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* Handle batching of page table freeing on SMP. Page tables are
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* queued up and send to be freed later by RCU in order to avoid
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* freeing a page table page that is being walked without locks
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*/
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static DEFINE_PER_CPU(struct pte_freelist_batch *, pte_freelist_cur);
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static unsigned long pte_freelist_forced_free;
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struct pte_freelist_batch
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{
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struct rcu_head rcu;
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unsigned int index;
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pgtable_free_t tables[0];
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};
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#define PTE_FREELIST_SIZE \
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((PAGE_SIZE - sizeof(struct pte_freelist_batch)) \
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/ sizeof(pgtable_free_t))
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static void pte_free_smp_sync(void *arg)
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{
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/* Do nothing, just ensure we sync with all CPUs */
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}
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/* This is only called when we are critically out of memory
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* (and fail to get a page in pte_free_tlb).
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*/
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static void pgtable_free_now(pgtable_free_t pgf)
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{
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pte_freelist_forced_free++;
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smp_call_function(pte_free_smp_sync, NULL, 1);
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pgtable_free(pgf);
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}
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static void pte_free_rcu_callback(struct rcu_head *head)
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{
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struct pte_freelist_batch *batch =
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container_of(head, struct pte_freelist_batch, rcu);
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unsigned int i;
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for (i = 0; i < batch->index; i++)
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pgtable_free(batch->tables[i]);
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free_page((unsigned long)batch);
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}
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static void pte_free_submit(struct pte_freelist_batch *batch)
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{
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INIT_RCU_HEAD(&batch->rcu);
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call_rcu(&batch->rcu, pte_free_rcu_callback);
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}
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void pgtable_free_tlb(struct mmu_gather *tlb, pgtable_free_t pgf)
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{
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/* This is safe since tlb_gather_mmu has disabled preemption */
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struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
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if (atomic_read(&tlb->mm->mm_users) < 2 ||
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cpumask_equal(mm_cpumask(tlb->mm), cpumask_of(smp_processor_id()))){
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pgtable_free(pgf);
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return;
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}
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if (*batchp == NULL) {
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*batchp = (struct pte_freelist_batch *)__get_free_page(GFP_ATOMIC);
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if (*batchp == NULL) {
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pgtable_free_now(pgf);
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return;
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}
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(*batchp)->index = 0;
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}
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(*batchp)->tables[(*batchp)->index++] = pgf;
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if ((*batchp)->index == PTE_FREELIST_SIZE) {
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pte_free_submit(*batchp);
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*batchp = NULL;
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}
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}
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void pte_free_finish(void)
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{
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/* This is safe since tlb_gather_mmu has disabled preemption */
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struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
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if (*batchp == NULL)
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return;
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pte_free_submit(*batchp);
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*batchp = NULL;
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}
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#endif /* CONFIG_SMP */
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static inline int is_exec_fault(void)
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{
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return current->thread.regs && TRAP(current->thread.regs) == 0x400;
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}
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/* We only try to do i/d cache coherency on stuff that looks like
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* reasonably "normal" PTEs. We currently require a PTE to be present
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* and we avoid _PAGE_SPECIAL and _PAGE_NO_CACHE. We also only do that
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* on userspace PTEs
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*/
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static inline int pte_looks_normal(pte_t pte)
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{
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return (pte_val(pte) &
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(_PAGE_PRESENT | _PAGE_SPECIAL | _PAGE_NO_CACHE | _PAGE_USER)) ==
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(_PAGE_PRESENT | _PAGE_USER);
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}
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struct page * maybe_pte_to_page(pte_t pte)
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{
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unsigned long pfn = pte_pfn(pte);
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struct page *page;
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if (unlikely(!pfn_valid(pfn)))
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return NULL;
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page = pfn_to_page(pfn);
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if (PageReserved(page))
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return NULL;
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return page;
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}
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#if defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0
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/* Server-style MMU handles coherency when hashing if HW exec permission
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* is supposed per page (currently 64-bit only). If not, then, we always
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* flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec
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* support falls into the same category.
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*/
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static pte_t set_pte_filter(pte_t pte, unsigned long addr)
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{
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pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
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if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) ||
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cpu_has_feature(CPU_FTR_NOEXECUTE))) {
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struct page *pg = maybe_pte_to_page(pte);
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if (!pg)
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return pte;
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if (!test_bit(PG_arch_1, &pg->flags)) {
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#ifdef CONFIG_8xx
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/* On 8xx, cache control instructions (particularly
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* "dcbst" from flush_dcache_icache) fault as write
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* operation if there is an unpopulated TLB entry
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* for the address in question. To workaround that,
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* we invalidate the TLB here, thus avoiding dcbst
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* misbehaviour.
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*/
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/* 8xx doesn't care about PID, size or ind args */
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_tlbil_va(addr, 0, 0, 0);
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#endif /* CONFIG_8xx */
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flush_dcache_icache_page(pg);
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set_bit(PG_arch_1, &pg->flags);
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}
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}
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return pte;
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}
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static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma,
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int dirty)
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{
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return pte;
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}
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#else /* defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 */
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/* Embedded type MMU with HW exec support. This is a bit more complicated
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* as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so
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* instead we "filter out" the exec permission for non clean pages.
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*/
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static pte_t set_pte_filter(pte_t pte, unsigned long addr)
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{
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struct page *pg;
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/* No exec permission in the first place, move on */
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if (!(pte_val(pte) & _PAGE_EXEC) || !pte_looks_normal(pte))
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return pte;
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/* If you set _PAGE_EXEC on weird pages you're on your own */
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pg = maybe_pte_to_page(pte);
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if (unlikely(!pg))
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return pte;
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/* If the page clean, we move on */
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if (test_bit(PG_arch_1, &pg->flags))
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return pte;
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/* If it's an exec fault, we flush the cache and make it clean */
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if (is_exec_fault()) {
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flush_dcache_icache_page(pg);
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set_bit(PG_arch_1, &pg->flags);
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return pte;
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}
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/* Else, we filter out _PAGE_EXEC */
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return __pte(pte_val(pte) & ~_PAGE_EXEC);
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}
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static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma,
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int dirty)
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{
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struct page *pg;
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/* So here, we only care about exec faults, as we use them
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* to recover lost _PAGE_EXEC and perform I$/D$ coherency
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* if necessary. Also if _PAGE_EXEC is already set, same deal,
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* we just bail out
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*/
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if (dirty || (pte_val(pte) & _PAGE_EXEC) || !is_exec_fault())
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return pte;
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#ifdef CONFIG_DEBUG_VM
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/* So this is an exec fault, _PAGE_EXEC is not set. If it was
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* an error we would have bailed out earlier in do_page_fault()
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* but let's make sure of it
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*/
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if (WARN_ON(!(vma->vm_flags & VM_EXEC)))
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return pte;
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#endif /* CONFIG_DEBUG_VM */
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/* If you set _PAGE_EXEC on weird pages you're on your own */
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pg = maybe_pte_to_page(pte);
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if (unlikely(!pg))
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goto bail;
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/* If the page is already clean, we move on */
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if (test_bit(PG_arch_1, &pg->flags))
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goto bail;
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/* Clean the page and set PG_arch_1 */
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flush_dcache_icache_page(pg);
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set_bit(PG_arch_1, &pg->flags);
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bail:
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return __pte(pte_val(pte) | _PAGE_EXEC);
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}
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#endif /* !(defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0) */
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/*
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* set_pte stores a linux PTE into the linux page table.
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*/
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void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
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pte_t pte)
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{
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#ifdef CONFIG_DEBUG_VM
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WARN_ON(pte_present(*ptep));
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#endif
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/* Note: mm->context.id might not yet have been assigned as
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* this context might not have been activated yet when this
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* is called.
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*/
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pte = set_pte_filter(pte, addr);
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/* Perform the setting of the PTE */
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__set_pte_at(mm, addr, ptep, pte, 0);
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}
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/*
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* This is called when relaxing access to a PTE. It's also called in the page
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* fault path when we don't hit any of the major fault cases, ie, a minor
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* update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have
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* handled those two for us, we additionally deal with missing execute
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* permission here on some processors
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*/
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int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address,
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pte_t *ptep, pte_t entry, int dirty)
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{
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int changed;
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entry = set_access_flags_filter(entry, vma, dirty);
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changed = !pte_same(*(ptep), entry);
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if (changed) {
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if (!(vma->vm_flags & VM_HUGETLB))
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assert_pte_locked(vma->vm_mm, address);
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__ptep_set_access_flags(ptep, entry);
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flush_tlb_page_nohash(vma, address);
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}
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return changed;
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}
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#ifdef CONFIG_DEBUG_VM
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void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
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{
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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if (mm == &init_mm)
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return;
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pgd = mm->pgd + pgd_index(addr);
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BUG_ON(pgd_none(*pgd));
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pud = pud_offset(pgd, addr);
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BUG_ON(pud_none(*pud));
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pmd = pmd_offset(pud, addr);
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BUG_ON(!pmd_present(*pmd));
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assert_spin_locked(pte_lockptr(mm, pmd));
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}
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#endif /* CONFIG_DEBUG_VM */
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