From d7e28ffe6c74416b54345d6004fd0964c115b12c Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Thu, 19 Jul 2007 01:49:23 -0700 Subject: 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 Cc: Andi Kleen Cc: Eric Dumazet Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/lguest/page_tables.c | 411 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 411 insertions(+) create mode 100644 drivers/lguest/page_tables.c (limited to 'drivers/lguest/page_tables.c') diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c new file mode 100644 index 00000000000..1b0ba09b126 --- /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 +#include +#include +#include +#include +#include +#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(); +} -- cgit v1.2.3