lguest: the host code
This is the code for the "lg.ko" module, which allows lguest guests to
be launched.
[akpm@linux-foundation.org: update for futex-new-private-futexes]
[akpm@linux-foundation.org: build fix]
[jmorris@namei.org: lguest: use hrtimers]
[akpm@linux-foundation.org: x86_64 build fix]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
new file mode 100644
index 0000000..1b0ba09
--- /dev/null
+++ b/drivers/lguest/page_tables.c
@@ -0,0 +1,411 @@
+/* Shadow page table operations.
+ * Copyright (C) Rusty Russell IBM Corporation 2006.
+ * GPL v2 and any later version */
+#include <linux/mm.h>
+#include <linux/types.h>
+#include <linux/spinlock.h>
+#include <linux/random.h>
+#include <linux/percpu.h>
+#include <asm/tlbflush.h>
+#include "lg.h"
+
+#define PTES_PER_PAGE_SHIFT 10
+#define PTES_PER_PAGE (1 << PTES_PER_PAGE_SHIFT)
+#define SWITCHER_PGD_INDEX (PTES_PER_PAGE - 1)
+
+static DEFINE_PER_CPU(spte_t *, switcher_pte_pages);
+#define switcher_pte_page(cpu) per_cpu(switcher_pte_pages, cpu)
+
+static unsigned vaddr_to_pgd_index(unsigned long vaddr)
+{
+ return vaddr >> (PAGE_SHIFT + PTES_PER_PAGE_SHIFT);
+}
+
+/* These access the shadow versions (ie. the ones used by the CPU). */
+static spgd_t *spgd_addr(struct lguest *lg, u32 i, unsigned long vaddr)
+{
+ unsigned int index = vaddr_to_pgd_index(vaddr);
+
+ if (index >= SWITCHER_PGD_INDEX) {
+ kill_guest(lg, "attempt to access switcher pages");
+ index = 0;
+ }
+ return &lg->pgdirs[i].pgdir[index];
+}
+
+static spte_t *spte_addr(struct lguest *lg, spgd_t spgd, unsigned long vaddr)
+{
+ spte_t *page = __va(spgd.pfn << PAGE_SHIFT);
+ BUG_ON(!(spgd.flags & _PAGE_PRESENT));
+ return &page[(vaddr >> PAGE_SHIFT) % PTES_PER_PAGE];
+}
+
+/* These access the guest versions. */
+static unsigned long gpgd_addr(struct lguest *lg, unsigned long vaddr)
+{
+ unsigned int index = vaddr >> (PAGE_SHIFT + PTES_PER_PAGE_SHIFT);
+ return lg->pgdirs[lg->pgdidx].cr3 + index * sizeof(gpgd_t);
+}
+
+static unsigned long gpte_addr(struct lguest *lg,
+ gpgd_t gpgd, unsigned long vaddr)
+{
+ unsigned long gpage = gpgd.pfn << PAGE_SHIFT;
+ BUG_ON(!(gpgd.flags & _PAGE_PRESENT));
+ return gpage + ((vaddr>>PAGE_SHIFT) % PTES_PER_PAGE) * sizeof(gpte_t);
+}
+
+/* Do a virtual -> physical mapping on a user page. */
+static unsigned long get_pfn(unsigned long virtpfn, int write)
+{
+ struct page *page;
+ unsigned long ret = -1UL;
+
+ down_read(¤t->mm->mmap_sem);
+ if (get_user_pages(current, current->mm, virtpfn << PAGE_SHIFT,
+ 1, write, 1, &page, NULL) == 1)
+ ret = page_to_pfn(page);
+ up_read(¤t->mm->mmap_sem);
+ return ret;
+}
+
+static spte_t gpte_to_spte(struct lguest *lg, gpte_t gpte, int write)
+{
+ spte_t spte;
+ unsigned long pfn;
+
+ /* We ignore the global flag. */
+ spte.flags = (gpte.flags & ~_PAGE_GLOBAL);
+ pfn = get_pfn(gpte.pfn, write);
+ if (pfn == -1UL) {
+ kill_guest(lg, "failed to get page %u", gpte.pfn);
+ /* Must not put_page() bogus page on cleanup. */
+ spte.flags = 0;
+ }
+ spte.pfn = pfn;
+ return spte;
+}
+
+static void release_pte(spte_t pte)
+{
+ if (pte.flags & _PAGE_PRESENT)
+ put_page(pfn_to_page(pte.pfn));
+}
+
+static void check_gpte(struct lguest *lg, gpte_t gpte)
+{
+ if ((gpte.flags & (_PAGE_PWT|_PAGE_PSE)) || gpte.pfn >= lg->pfn_limit)
+ kill_guest(lg, "bad page table entry");
+}
+
+static void check_gpgd(struct lguest *lg, gpgd_t gpgd)
+{
+ if ((gpgd.flags & ~_PAGE_TABLE) || gpgd.pfn >= lg->pfn_limit)
+ kill_guest(lg, "bad page directory entry");
+}
+
+/* FIXME: We hold reference to pages, which prevents them from being
+ swapped. It'd be nice to have a callback when Linux wants to swap out. */
+
+/* We fault pages in, which allows us to update accessed/dirty bits.
+ * Return true if we got page. */
+int demand_page(struct lguest *lg, unsigned long vaddr, int errcode)
+{
+ gpgd_t gpgd;
+ spgd_t *spgd;
+ unsigned long gpte_ptr;
+ gpte_t gpte;
+ spte_t *spte;
+
+ gpgd = mkgpgd(lgread_u32(lg, gpgd_addr(lg, vaddr)));
+ if (!(gpgd.flags & _PAGE_PRESENT))
+ return 0;
+
+ spgd = spgd_addr(lg, lg->pgdidx, vaddr);
+ if (!(spgd->flags & _PAGE_PRESENT)) {
+ /* Get a page of PTEs for them. */
+ unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
+ /* FIXME: Steal from self in this case? */
+ if (!ptepage) {
+ kill_guest(lg, "out of memory allocating pte page");
+ return 0;
+ }
+ check_gpgd(lg, gpgd);
+ spgd->raw.val = (__pa(ptepage) | gpgd.flags);
+ }
+
+ gpte_ptr = gpte_addr(lg, gpgd, vaddr);
+ gpte = mkgpte(lgread_u32(lg, gpte_ptr));
+
+ /* No page? */
+ if (!(gpte.flags & _PAGE_PRESENT))
+ return 0;
+
+ /* Write to read-only page? */
+ if ((errcode & 2) && !(gpte.flags & _PAGE_RW))
+ return 0;
+
+ /* User access to a non-user page? */
+ if ((errcode & 4) && !(gpte.flags & _PAGE_USER))
+ return 0;
+
+ check_gpte(lg, gpte);
+ gpte.flags |= _PAGE_ACCESSED;
+ if (errcode & 2)
+ gpte.flags |= _PAGE_DIRTY;
+
+ /* We're done with the old pte. */
+ spte = spte_addr(lg, *spgd, vaddr);
+ release_pte(*spte);
+
+ /* We don't make it writable if this isn't a write: later
+ * write will fault so we can set dirty bit in guest. */
+ if (gpte.flags & _PAGE_DIRTY)
+ *spte = gpte_to_spte(lg, gpte, 1);
+ else {
+ gpte_t ro_gpte = gpte;
+ ro_gpte.flags &= ~_PAGE_RW;
+ *spte = gpte_to_spte(lg, ro_gpte, 0);
+ }
+
+ /* Now we update dirty/accessed on guest. */
+ lgwrite_u32(lg, gpte_ptr, gpte.raw.val);
+ return 1;
+}
+
+/* This is much faster than the full demand_page logic. */
+static int page_writable(struct lguest *lg, unsigned long vaddr)
+{
+ spgd_t *spgd;
+ unsigned long flags;
+
+ spgd = spgd_addr(lg, lg->pgdidx, vaddr);
+ if (!(spgd->flags & _PAGE_PRESENT))
+ return 0;
+
+ flags = spte_addr(lg, *spgd, vaddr)->flags;
+ return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW);
+}
+
+void pin_page(struct lguest *lg, unsigned long vaddr)
+{
+ if (!page_writable(lg, vaddr) && !demand_page(lg, vaddr, 2))
+ kill_guest(lg, "bad stack page %#lx", vaddr);
+}
+
+static void release_pgd(struct lguest *lg, spgd_t *spgd)
+{
+ if (spgd->flags & _PAGE_PRESENT) {
+ unsigned int i;
+ spte_t *ptepage = __va(spgd->pfn << PAGE_SHIFT);
+ for (i = 0; i < PTES_PER_PAGE; i++)
+ release_pte(ptepage[i]);
+ free_page((long)ptepage);
+ spgd->raw.val = 0;
+ }
+}
+
+static void flush_user_mappings(struct lguest *lg, int idx)
+{
+ unsigned int i;
+ for (i = 0; i < vaddr_to_pgd_index(lg->page_offset); i++)
+ release_pgd(lg, lg->pgdirs[idx].pgdir + i);
+}
+
+void guest_pagetable_flush_user(struct lguest *lg)
+{
+ flush_user_mappings(lg, lg->pgdidx);
+}
+
+static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable)
+{
+ unsigned int i;
+ for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
+ if (lg->pgdirs[i].cr3 == pgtable)
+ break;
+ return i;
+}
+
+static unsigned int new_pgdir(struct lguest *lg,
+ unsigned long cr3,
+ int *blank_pgdir)
+{
+ unsigned int next;
+
+ next = random32() % ARRAY_SIZE(lg->pgdirs);
+ if (!lg->pgdirs[next].pgdir) {
+ lg->pgdirs[next].pgdir = (spgd_t *)get_zeroed_page(GFP_KERNEL);
+ if (!lg->pgdirs[next].pgdir)
+ next = lg->pgdidx;
+ else
+ /* There are no mappings: you'll need to re-pin */
+ *blank_pgdir = 1;
+ }
+ lg->pgdirs[next].cr3 = cr3;
+ /* Release all the non-kernel mappings. */
+ flush_user_mappings(lg, next);
+
+ return next;
+}
+
+void guest_new_pagetable(struct lguest *lg, unsigned long pgtable)
+{
+ int newpgdir, repin = 0;
+
+ newpgdir = find_pgdir(lg, pgtable);
+ if (newpgdir == ARRAY_SIZE(lg->pgdirs))
+ newpgdir = new_pgdir(lg, pgtable, &repin);
+ lg->pgdidx = newpgdir;
+ if (repin)
+ pin_stack_pages(lg);
+}
+
+static void release_all_pagetables(struct lguest *lg)
+{
+ unsigned int i, j;
+
+ for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
+ if (lg->pgdirs[i].pgdir)
+ for (j = 0; j < SWITCHER_PGD_INDEX; j++)
+ release_pgd(lg, lg->pgdirs[i].pgdir + j);
+}
+
+void guest_pagetable_clear_all(struct lguest *lg)
+{
+ release_all_pagetables(lg);
+ pin_stack_pages(lg);
+}
+
+static void do_set_pte(struct lguest *lg, int idx,
+ unsigned long vaddr, gpte_t gpte)
+{
+ spgd_t *spgd = spgd_addr(lg, idx, vaddr);
+ if (spgd->flags & _PAGE_PRESENT) {
+ spte_t *spte = spte_addr(lg, *spgd, vaddr);
+ release_pte(*spte);
+ if (gpte.flags & (_PAGE_DIRTY | _PAGE_ACCESSED)) {
+ check_gpte(lg, gpte);
+ *spte = gpte_to_spte(lg, gpte, gpte.flags&_PAGE_DIRTY);
+ } else
+ spte->raw.val = 0;
+ }
+}
+
+void guest_set_pte(struct lguest *lg,
+ unsigned long cr3, unsigned long vaddr, gpte_t gpte)
+{
+ /* Kernel mappings must be changed on all top levels. */
+ if (vaddr >= lg->page_offset) {
+ unsigned int i;
+ for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
+ if (lg->pgdirs[i].pgdir)
+ do_set_pte(lg, i, vaddr, gpte);
+ } else {
+ int pgdir = find_pgdir(lg, cr3);
+ if (pgdir != ARRAY_SIZE(lg->pgdirs))
+ do_set_pte(lg, pgdir, vaddr, gpte);
+ }
+}
+
+void guest_set_pmd(struct lguest *lg, unsigned long cr3, u32 idx)
+{
+ int pgdir;
+
+ if (idx >= SWITCHER_PGD_INDEX)
+ return;
+
+ pgdir = find_pgdir(lg, cr3);
+ if (pgdir < ARRAY_SIZE(lg->pgdirs))
+ release_pgd(lg, lg->pgdirs[pgdir].pgdir + idx);
+}
+
+int init_guest_pagetable(struct lguest *lg, unsigned long pgtable)
+{
+ /* We assume this in flush_user_mappings, so check now */
+ if (vaddr_to_pgd_index(lg->page_offset) >= SWITCHER_PGD_INDEX)
+ return -EINVAL;
+ lg->pgdidx = 0;
+ lg->pgdirs[lg->pgdidx].cr3 = pgtable;
+ lg->pgdirs[lg->pgdidx].pgdir = (spgd_t*)get_zeroed_page(GFP_KERNEL);
+ if (!lg->pgdirs[lg->pgdidx].pgdir)
+ return -ENOMEM;
+ return 0;
+}
+
+void free_guest_pagetable(struct lguest *lg)
+{
+ unsigned int i;
+
+ release_all_pagetables(lg);
+ for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
+ free_page((long)lg->pgdirs[i].pgdir);
+}
+
+/* Caller must be preempt-safe */
+void map_switcher_in_guest(struct lguest *lg, struct lguest_pages *pages)
+{
+ spte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages);
+ spgd_t switcher_pgd;
+ spte_t regs_pte;
+
+ /* Since switcher less that 4MB, we simply mug top pte page. */
+ 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();
+}