LXR linux/arch/um/kernel/skas/mmu.c

   1/*
   2 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3 * Licensed under the GPL
   4 */
   5
   6#include <linux/mm.h>
   7#include <linux/sched.h>
   8#include <linux/slab.h>
   9#include <asm/pgalloc.h>
  10#include <asm/pgtable.h>
  11#include <as-layout.h>
  12#include <os.h>
  13#include <skas.h>
  14
  15extern int __syscall_stub_start;
  16
  17static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
  18                         unsigned long kernel)
  19{
  20        pgd_t *pgd;
  21        pud_t *pud;
  22        pmd_t *pmd;
  23        pte_t *pte;
  24
  25        pgd = pgd_offset(mm, proc);
  26        pud = pud_alloc(mm, pgd, proc);
  27        if (!pud)
  28                goto out;
  29
  30        pmd = pmd_alloc(mm, pud, proc);
  31        if (!pmd)
  32                goto out_pmd;
  33
  34        pte = pte_alloc_map(mm, NULL, pmd, proc);
  35        if (!pte)
  36                goto out_pte;
  37
  38        *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
  39        *pte = pte_mkread(*pte);
  40        return 0;
  41
  42 out_pte:
  43        pmd_free(mm, pmd);
  44 out_pmd:
  45        pud_free(mm, pud);
  46 out:
  47        return -ENOMEM;
  48}
  49
  50int init_new_context(struct task_struct *task, struct mm_struct *mm)
  51{
  52        struct mm_context *from_mm = NULL;
  53        struct mm_context *to_mm = &mm->context;
  54        unsigned long stack = 0;
  55        int ret = -ENOMEM;
  56
  57        if (skas_needs_stub) {
  58                stack = get_zeroed_page(GFP_KERNEL);
  59                if (stack == 0)
  60                        goto out;
  61        }
  62
  63        to_mm->id.stack = stack;
  64        if (current->mm != NULL && current->mm != &init_mm)
  65                from_mm = &current->mm->context;
  66
  67        if (proc_mm) {
  68                ret = new_mm(stack);
  69                if (ret < 0) {
  70                        printk(KERN_ERR "init_new_context_skas - "
  71                               "new_mm failed, errno = %d\n", ret);
  72                        goto out_free;
  73                }
  74                to_mm->id.u.mm_fd = ret;
  75        }
  76        else {
  77                if (from_mm)
  78                        to_mm->id.u.pid = copy_context_skas0(stack,
  79                                                             from_mm->id.u.pid);
  80                else to_mm->id.u.pid = start_userspace(stack);
  81
  82                if (to_mm->id.u.pid < 0) {
  83                        ret = to_mm->id.u.pid;
  84                        goto out_free;
  85                }
  86        }
  87
  88        ret = init_new_ldt(to_mm, from_mm);
  89        if (ret < 0) {
  90                printk(KERN_ERR "init_new_context_skas - init_ldt"
  91                       " failed, errno = %d\n", ret);
  92                goto out_free;
  93        }
  94
  95        return 0;
  96
  97 out_free:
  98        if (to_mm->id.stack != 0)
  99                free_page(to_mm->id.stack);
 100 out:
 101        return ret;
 102}
 103
 104void uml_setup_stubs(struct mm_struct *mm)
 105{
 106        int err, ret;
 107
 108        if (!skas_needs_stub)
 109                return;
 110
 111        ret = init_stub_pte(mm, STUB_CODE,
 112                            (unsigned long) &__syscall_stub_start);
 113        if (ret)
 114                goto out;
 115
 116        ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
 117        if (ret)
 118                goto out;
 119
 120        mm->context.stub_pages[0] = virt_to_page(&__syscall_stub_start);
 121        mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
 122
 123        /* dup_mmap already holds mmap_sem */
 124        err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
 125                                      VM_READ | VM_MAYREAD | VM_EXEC |
 126                                      VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP,
 127                                      mm->context.stub_pages);
 128        if (err) {
 129                printk(KERN_ERR "install_special_mapping returned %d\n", err);
 130                goto out;
 131        }
 132        return;
 133
 134out:
 135        force_sigsegv(SIGSEGV, current);
 136}
 137
 138void arch_exit_mmap(struct mm_struct *mm)
 139{
 140        pte_t *pte;
 141
 142        pte = virt_to_pte(mm, STUB_CODE);
 143        if (pte != NULL)
 144                pte_clear(mm, STUB_CODE, pte);
 145
 146        pte = virt_to_pte(mm, STUB_DATA);
 147        if (pte == NULL)
 148                return;
 149
 150        pte_clear(mm, STUB_DATA, pte);
 151}
 152
 153void destroy_context(struct mm_struct *mm)
 154{
 155        struct mm_context *mmu = &mm->context;
 156
 157        if (proc_mm)
 158                os_close_file(mmu->id.u.mm_fd);
 159        else {
 160                /*
 161                 * If init_new_context wasn't called, this will be
 162                 * zero, resulting in a kill(0), which will result in the
 163                 * whole UML suddenly dying.  Also, cover negative and
 164                 * 1 cases, since they shouldn't happen either.
 165                 */
 166                if (mmu->id.u.pid < 2) {
 167                        printk(KERN_ERR "corrupt mm_context - pid = %d\n",
 168                               mmu->id.u.pid);
 169                        return;
 170                }
 171                os_kill_ptraced_process(mmu->id.u.pid, 1);
 172        }
 173
 174        if (skas_needs_stub)
 175                free_page(mmu->id.stack);
 176
 177        free_ldt(mmu);
 178}
 179