412 lines
10 KiB
C
412 lines
10 KiB
C
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/* Shadow page table operations.
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* Copyright (C) Rusty Russell IBM Corporation 2006.
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* GPL v2 and any later version */
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#include <linux/mm.h>
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#include <linux/types.h>
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#include <linux/spinlock.h>
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#include <linux/random.h>
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#include <linux/percpu.h>
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#include <asm/tlbflush.h>
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#include "lg.h"
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#define PTES_PER_PAGE_SHIFT 10
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#define PTES_PER_PAGE (1 << PTES_PER_PAGE_SHIFT)
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#define SWITCHER_PGD_INDEX (PTES_PER_PAGE - 1)
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static DEFINE_PER_CPU(spte_t *, switcher_pte_pages);
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#define switcher_pte_page(cpu) per_cpu(switcher_pte_pages, cpu)
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static unsigned vaddr_to_pgd_index(unsigned long vaddr)
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{
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return vaddr >> (PAGE_SHIFT + PTES_PER_PAGE_SHIFT);
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}
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/* These access the shadow versions (ie. the ones used by the CPU). */
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static spgd_t *spgd_addr(struct lguest *lg, u32 i, unsigned long vaddr)
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{
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unsigned int index = vaddr_to_pgd_index(vaddr);
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if (index >= SWITCHER_PGD_INDEX) {
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kill_guest(lg, "attempt to access switcher pages");
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index = 0;
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}
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return &lg->pgdirs[i].pgdir[index];
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}
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static spte_t *spte_addr(struct lguest *lg, spgd_t spgd, unsigned long vaddr)
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{
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spte_t *page = __va(spgd.pfn << PAGE_SHIFT);
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BUG_ON(!(spgd.flags & _PAGE_PRESENT));
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return &page[(vaddr >> PAGE_SHIFT) % PTES_PER_PAGE];
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}
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/* These access the guest versions. */
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static unsigned long gpgd_addr(struct lguest *lg, unsigned long vaddr)
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{
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unsigned int index = vaddr >> (PAGE_SHIFT + PTES_PER_PAGE_SHIFT);
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return lg->pgdirs[lg->pgdidx].cr3 + index * sizeof(gpgd_t);
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}
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static unsigned long gpte_addr(struct lguest *lg,
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gpgd_t gpgd, unsigned long vaddr)
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{
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unsigned long gpage = gpgd.pfn << PAGE_SHIFT;
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BUG_ON(!(gpgd.flags & _PAGE_PRESENT));
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return gpage + ((vaddr>>PAGE_SHIFT) % PTES_PER_PAGE) * sizeof(gpte_t);
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}
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/* Do a virtual -> physical mapping on a user page. */
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static unsigned long get_pfn(unsigned long virtpfn, int write)
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{
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struct page *page;
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unsigned long ret = -1UL;
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down_read(¤t->mm->mmap_sem);
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if (get_user_pages(current, current->mm, virtpfn << PAGE_SHIFT,
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1, write, 1, &page, NULL) == 1)
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ret = page_to_pfn(page);
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up_read(¤t->mm->mmap_sem);
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return ret;
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}
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static spte_t gpte_to_spte(struct lguest *lg, gpte_t gpte, int write)
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{
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spte_t spte;
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unsigned long pfn;
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/* We ignore the global flag. */
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spte.flags = (gpte.flags & ~_PAGE_GLOBAL);
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pfn = get_pfn(gpte.pfn, write);
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if (pfn == -1UL) {
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kill_guest(lg, "failed to get page %u", gpte.pfn);
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/* Must not put_page() bogus page on cleanup. */
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spte.flags = 0;
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}
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spte.pfn = pfn;
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return spte;
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}
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static void release_pte(spte_t pte)
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{
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if (pte.flags & _PAGE_PRESENT)
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put_page(pfn_to_page(pte.pfn));
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}
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static void check_gpte(struct lguest *lg, gpte_t gpte)
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{
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if ((gpte.flags & (_PAGE_PWT|_PAGE_PSE)) || gpte.pfn >= lg->pfn_limit)
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kill_guest(lg, "bad page table entry");
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}
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static void check_gpgd(struct lguest *lg, gpgd_t gpgd)
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{
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if ((gpgd.flags & ~_PAGE_TABLE) || gpgd.pfn >= lg->pfn_limit)
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kill_guest(lg, "bad page directory entry");
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}
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/* FIXME: We hold reference to pages, which prevents them from being
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swapped. It'd be nice to have a callback when Linux wants to swap out. */
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/* We fault pages in, which allows us to update accessed/dirty bits.
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* Return true if we got page. */
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int demand_page(struct lguest *lg, unsigned long vaddr, int errcode)
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{
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gpgd_t gpgd;
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spgd_t *spgd;
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unsigned long gpte_ptr;
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gpte_t gpte;
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spte_t *spte;
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gpgd = mkgpgd(lgread_u32(lg, gpgd_addr(lg, vaddr)));
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if (!(gpgd.flags & _PAGE_PRESENT))
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return 0;
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spgd = spgd_addr(lg, lg->pgdidx, vaddr);
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if (!(spgd->flags & _PAGE_PRESENT)) {
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/* Get a page of PTEs for them. */
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unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
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/* FIXME: Steal from self in this case? */
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if (!ptepage) {
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kill_guest(lg, "out of memory allocating pte page");
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return 0;
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}
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check_gpgd(lg, gpgd);
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spgd->raw.val = (__pa(ptepage) | gpgd.flags);
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}
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gpte_ptr = gpte_addr(lg, gpgd, vaddr);
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gpte = mkgpte(lgread_u32(lg, gpte_ptr));
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/* No page? */
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if (!(gpte.flags & _PAGE_PRESENT))
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return 0;
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/* Write to read-only page? */
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if ((errcode & 2) && !(gpte.flags & _PAGE_RW))
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return 0;
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/* User access to a non-user page? */
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if ((errcode & 4) && !(gpte.flags & _PAGE_USER))
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return 0;
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check_gpte(lg, gpte);
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gpte.flags |= _PAGE_ACCESSED;
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if (errcode & 2)
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gpte.flags |= _PAGE_DIRTY;
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/* We're done with the old pte. */
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spte = spte_addr(lg, *spgd, vaddr);
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release_pte(*spte);
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/* We don't make it writable if this isn't a write: later
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* write will fault so we can set dirty bit in guest. */
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if (gpte.flags & _PAGE_DIRTY)
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*spte = gpte_to_spte(lg, gpte, 1);
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else {
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gpte_t ro_gpte = gpte;
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ro_gpte.flags &= ~_PAGE_RW;
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*spte = gpte_to_spte(lg, ro_gpte, 0);
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}
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/* Now we update dirty/accessed on guest. */
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lgwrite_u32(lg, gpte_ptr, gpte.raw.val);
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return 1;
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}
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/* This is much faster than the full demand_page logic. */
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static int page_writable(struct lguest *lg, unsigned long vaddr)
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{
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spgd_t *spgd;
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unsigned long flags;
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spgd = spgd_addr(lg, lg->pgdidx, vaddr);
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if (!(spgd->flags & _PAGE_PRESENT))
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return 0;
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flags = spte_addr(lg, *spgd, vaddr)->flags;
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return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW);
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}
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void pin_page(struct lguest *lg, unsigned long vaddr)
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{
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if (!page_writable(lg, vaddr) && !demand_page(lg, vaddr, 2))
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kill_guest(lg, "bad stack page %#lx", vaddr);
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}
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static void release_pgd(struct lguest *lg, spgd_t *spgd)
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{
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if (spgd->flags & _PAGE_PRESENT) {
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unsigned int i;
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spte_t *ptepage = __va(spgd->pfn << PAGE_SHIFT);
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for (i = 0; i < PTES_PER_PAGE; i++)
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release_pte(ptepage[i]);
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free_page((long)ptepage);
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spgd->raw.val = 0;
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}
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}
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static void flush_user_mappings(struct lguest *lg, int idx)
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{
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unsigned int i;
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for (i = 0; i < vaddr_to_pgd_index(lg->page_offset); i++)
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release_pgd(lg, lg->pgdirs[idx].pgdir + i);
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}
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void guest_pagetable_flush_user(struct lguest *lg)
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{
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flush_user_mappings(lg, lg->pgdidx);
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}
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static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable)
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{
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unsigned int i;
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for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
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if (lg->pgdirs[i].cr3 == pgtable)
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break;
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return i;
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}
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static unsigned int new_pgdir(struct lguest *lg,
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unsigned long cr3,
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int *blank_pgdir)
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{
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unsigned int next;
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next = random32() % ARRAY_SIZE(lg->pgdirs);
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if (!lg->pgdirs[next].pgdir) {
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lg->pgdirs[next].pgdir = (spgd_t *)get_zeroed_page(GFP_KERNEL);
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if (!lg->pgdirs[next].pgdir)
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next = lg->pgdidx;
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else
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/* There are no mappings: you'll need to re-pin */
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*blank_pgdir = 1;
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}
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lg->pgdirs[next].cr3 = cr3;
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/* Release all the non-kernel mappings. */
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flush_user_mappings(lg, next);
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return next;
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}
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void guest_new_pagetable(struct lguest *lg, unsigned long pgtable)
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{
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int newpgdir, repin = 0;
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newpgdir = find_pgdir(lg, pgtable);
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if (newpgdir == ARRAY_SIZE(lg->pgdirs))
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newpgdir = new_pgdir(lg, pgtable, &repin);
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lg->pgdidx = newpgdir;
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if (repin)
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pin_stack_pages(lg);
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}
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static void release_all_pagetables(struct lguest *lg)
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{
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unsigned int i, j;
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for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
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if (lg->pgdirs[i].pgdir)
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for (j = 0; j < SWITCHER_PGD_INDEX; j++)
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release_pgd(lg, lg->pgdirs[i].pgdir + j);
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}
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void guest_pagetable_clear_all(struct lguest *lg)
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{
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release_all_pagetables(lg);
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pin_stack_pages(lg);
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}
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static void do_set_pte(struct lguest *lg, int idx,
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unsigned long vaddr, gpte_t gpte)
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{
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spgd_t *spgd = spgd_addr(lg, idx, vaddr);
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if (spgd->flags & _PAGE_PRESENT) {
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spte_t *spte = spte_addr(lg, *spgd, vaddr);
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release_pte(*spte);
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if (gpte.flags & (_PAGE_DIRTY | _PAGE_ACCESSED)) {
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check_gpte(lg, gpte);
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*spte = gpte_to_spte(lg, gpte, gpte.flags&_PAGE_DIRTY);
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} else
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spte->raw.val = 0;
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}
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}
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void guest_set_pte(struct lguest *lg,
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unsigned long cr3, unsigned long vaddr, gpte_t gpte)
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{
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/* Kernel mappings must be changed on all top levels. */
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if (vaddr >= lg->page_offset) {
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unsigned int i;
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for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
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if (lg->pgdirs[i].pgdir)
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do_set_pte(lg, i, vaddr, gpte);
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} else {
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int pgdir = find_pgdir(lg, cr3);
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if (pgdir != ARRAY_SIZE(lg->pgdirs))
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do_set_pte(lg, pgdir, vaddr, gpte);
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}
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}
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void guest_set_pmd(struct lguest *lg, unsigned long cr3, u32 idx)
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{
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int pgdir;
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if (idx >= SWITCHER_PGD_INDEX)
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return;
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pgdir = find_pgdir(lg, cr3);
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if (pgdir < ARRAY_SIZE(lg->pgdirs))
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release_pgd(lg, lg->pgdirs[pgdir].pgdir + idx);
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}
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int init_guest_pagetable(struct lguest *lg, unsigned long pgtable)
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{
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/* We assume this in flush_user_mappings, so check now */
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if (vaddr_to_pgd_index(lg->page_offset) >= SWITCHER_PGD_INDEX)
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return -EINVAL;
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lg->pgdidx = 0;
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lg->pgdirs[lg->pgdidx].cr3 = pgtable;
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lg->pgdirs[lg->pgdidx].pgdir = (spgd_t*)get_zeroed_page(GFP_KERNEL);
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if (!lg->pgdirs[lg->pgdidx].pgdir)
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return -ENOMEM;
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return 0;
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}
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void free_guest_pagetable(struct lguest *lg)
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{
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unsigned int i;
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release_all_pagetables(lg);
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for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
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free_page((long)lg->pgdirs[i].pgdir);
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}
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/* Caller must be preempt-safe */
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void map_switcher_in_guest(struct lguest *lg, struct lguest_pages *pages)
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{
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spte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages);
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spgd_t switcher_pgd;
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spte_t regs_pte;
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/* Since switcher less that 4MB, we simply mug top pte page. */
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switcher_pgd.pfn = __pa(switcher_pte_page) >> PAGE_SHIFT;
|
||
|
|
switcher_pgd.flags = _PAGE_KERNEL;
|
||
|
|
lg->pgdirs[lg->pgdidx].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd;
|
||
|
|
|
||
|
|
/* Map our regs page over stack page. */
|
||
|
|
regs_pte.pfn = __pa(lg->regs_page) >> PAGE_SHIFT;
|
||
|
|
regs_pte.flags = _PAGE_KERNEL;
|
||
|
|
switcher_pte_page[(unsigned long)pages/PAGE_SIZE%PTES_PER_PAGE]
|
||
|
|
= regs_pte;
|
||
|
|
}
|
||
|
|
|
||
|
|
static void free_switcher_pte_pages(void)
|
||
|
|
{
|
||
|
|
unsigned int i;
|
||
|
|
|
||
|
|
for_each_possible_cpu(i)
|
||
|
|
free_page((long)switcher_pte_page(i));
|
||
|
|
}
|
||
|
|
|
||
|
|
static __init void populate_switcher_pte_page(unsigned int cpu,
|
||
|
|
struct page *switcher_page[],
|
||
|
|
unsigned int pages)
|
||
|
|
{
|
||
|
|
unsigned int i;
|
||
|
|
spte_t *pte = switcher_pte_page(cpu);
|
||
|
|
|
||
|
|
for (i = 0; i < pages; i++) {
|
||
|
|
pte[i].pfn = page_to_pfn(switcher_page[i]);
|
||
|
|
pte[i].flags = _PAGE_PRESENT|_PAGE_ACCESSED;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* We only map this CPU's pages, so guest can't see others. */
|
||
|
|
i = pages + cpu*2;
|
||
|
|
|
||
|
|
/* First page (regs) is rw, second (state) is ro. */
|
||
|
|
pte[i].pfn = page_to_pfn(switcher_page[i]);
|
||
|
|
pte[i].flags = _PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW;
|
||
|
|
pte[i+1].pfn = page_to_pfn(switcher_page[i+1]);
|
||
|
|
pte[i+1].flags = _PAGE_PRESENT|_PAGE_ACCESSED;
|
||
|
|
}
|
||
|
|
|
||
|
|
__init int init_pagetables(struct page **switcher_page, unsigned int pages)
|
||
|
|
{
|
||
|
|
unsigned int i;
|
||
|
|
|
||
|
|
for_each_possible_cpu(i) {
|
||
|
|
switcher_pte_page(i) = (spte_t *)get_zeroed_page(GFP_KERNEL);
|
||
|
|
if (!switcher_pte_page(i)) {
|
||
|
|
free_switcher_pte_pages();
|
||
|
|
return -ENOMEM;
|
||
|
|
}
|
||
|
|
populate_switcher_pte_page(i, switcher_page, pages);
|
||
|
|
}
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
void free_pagetables(void)
|
||
|
|
{
|
||
|
|
free_switcher_pte_pages();
|
||
|
|
}
|