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>

1 files changed, 411 insertions, 0 deletions

diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
new file mode 100644
index 000000000000..1b0ba09b1269
--- /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(&current->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(&current->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();
+}