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 "asm/pgalloc.h"
   9#include "asm/pgtable.h"
  10#include "as-layout.h"
  11#include "os.h"
  12#include "skas.h"
  13
  14extern int __syscall_stub_start;
  15
  16static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
  17                         unsigned long kernel)
  18{
  19        pgd_t *pgd;
  20        pud_t *pud;
  21        pmd_t *pmd;
  22        pte_t *pte;
  23
  24        pgd = pgd_offset(mm, proc);
  25        pud = pud_alloc(mm, pgd, proc);
  26        if (!pud)
  27                goto out;
  28
  29        pmd = pmd_alloc(mm, pud, proc);
  30        if (!pmd)
  31                goto out_pmd;
  32
  33        pte = pte_alloc_map(mm, pmd, proc);
  34        if (!pte)
  35                goto out_pte;
  36
  37        *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
  38        *pte = pte_mkread(*pte);
  39        return 0;
  40
  41 out_pte:
  42        pmd_free(mm, pmd);
  43 out_pmd:
  44        pud_free(mm, pud);
  45 out:
  46        return -ENOMEM;
  47}
  48
  49int init_new_context(struct task_struct *task, struct mm_struct *mm)
  50{
  51        struct mm_context *from_mm = NULL;
  52        struct mm_context *to_mm = &mm->context;
  53        unsigned long stack = 0;
  54        int ret = -ENOMEM;
  55
  56        if (skas_needs_stub) {
  57                stack = get_zeroed_page(GFP_KERNEL);
  58                if (stack == 0)
  59                        goto out;
  60        }
  61
  62        to_mm->id.stack = stack;
  63        if (current->mm != NULL && current->mm != &init_mm)
  64                from_mm = &current->mm->context;
  65
  66        if (proc_mm) {
  67                ret = new_mm(stack);
  68                if (ret < 0) {
  69                        printk(KERN_ERR "init_new_context_skas - "
  70                               "new_mm failed, errno = %d\n", ret);
  71                        goto out_free;
  72                }
  73                to_mm->id.u.mm_fd = ret;
  74        }
  75        else {
  76                if (from_mm)
  77                        to_mm->id.u.pid = copy_context_skas0(stack,
  78                                                             from_mm->id.u.pid);
  79                else to_mm->id.u.pid = start_userspace(stack);
  80
  81                if (to_mm->id.u.pid < 0) {
  82                        ret = to_mm->id.u.pid;
  83                        goto out_free;
  84                }
  85        }
  86
  87        ret = init_new_ldt(to_mm, from_mm);
  88        if (ret < 0) {
  89                printk(KERN_ERR "init_new_context_skas - init_ldt"
  90                       " failed, errno = %d\n", ret);
  91                goto out_free;
  92        }
  93
  94        to_mm->stub_pages = NULL;
  95
  96        return 0;
  97
  98 out_free:
  99        if (to_mm->id.stack != 0)
 100                free_page(to_mm->id.stack);
 101 out:
 102        return ret;
 103}
 104
 105void arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
 106{
 107        struct page **pages;
 108        int err, ret;
 109
 110        if (!skas_needs_stub)
 111                return;
 112
 113        ret = init_stub_pte(mm, STUB_CODE,
 114                            (unsigned long) &__syscall_stub_start);
 115        if (ret)
 116                goto out;
 117
 118        ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
 119        if (ret)
 120                goto out;
 121
 122        pages = kmalloc(2 * sizeof(struct page *), GFP_KERNEL);
 123        if (pages == NULL) {
 124                printk(KERN_ERR "arch_dup_mmap failed to allocate 2 page "
 125                       "pointers\n");
 126                goto out;
 127        }
 128
 129        pages[0] = virt_to_page(&__syscall_stub_start);
 130        pages[1] = virt_to_page(mm->context.id.stack);
 131        mm->context.stub_pages = pages;
 132
 133        /* dup_mmap already holds mmap_sem */
 134        err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
 135                                      VM_READ | VM_MAYREAD | VM_EXEC |
 136                                      VM_MAYEXEC | VM_DONTCOPY, pages);
 137        if (err) {
 138                printk(KERN_ERR "install_special_mapping returned %d\n", err);
 139                goto out_free;
 140        }
 141        return;
 142
 143out_free:
 144        kfree(pages);
 145out:
 146        force_sigsegv(SIGSEGV, current);
 147}
 148
 149void arch_exit_mmap(struct mm_struct *mm)
 150{
 151        pte_t *pte;
 152
 153        if (mm->context.stub_pages != NULL)
 154                kfree(mm->context.stub_pages);
 155        pte = virt_to_pte(mm, STUB_CODE);
 156        if (pte != NULL)
 157                pte_clear(mm, STUB_CODE, pte);
 158
 159        pte = virt_to_pte(mm, STUB_DATA);
 160        if (pte == NULL)
 161                return;
 162
 163        pte_clear(mm, STUB_DATA, pte);
 164}
 165
 166void destroy_context(struct mm_struct *mm)
 167{
 168        struct mm_context *mmu = &mm->context;
 169
 170        if (proc_mm)
 171                os_close_file(mmu->id.u.mm_fd);
 172        else {
 173                /*
 174                 * If init_new_context wasn't called, this will be
 175                 * zero, resulting in a kill(0), which will result in the
 176                 * whole UML suddenly dying.  Also, cover negative and
 177                 * 1 cases, since they shouldn't happen either.
 178                 */
 179                if (mmu->id.u.pid < 2) {
 180                        printk(KERN_ERR "corrupt mm_context - pid = %d\n",
 181                               mmu->id.u.pid);
 182                        return;
 183                }
 184                os_kill_ptraced_process(mmu->id.u.pid, 1);
 185        }
 186
 187        if (skas_needs_stub)
 188                free_page(mmu->id.stack);
 189
 190        free_ldt(mmu);
 191}
 192