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
  15 extern int __syscall_stub_start;
  16
  17 static 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
  50 int 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         to_mm->stub_pages = NULL;
  96
  97         return 0;
  98
  99  out_free:
 100         if (to_mm->id.stack != 0)
 101                 free_page(to_mm->id.stack);
 102  out:
 103         return ret;
 104 }
 105
 106 void arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
 107 {
 108         struct page **pages;
 109         int err, ret;
 110
 111         if (!skas_needs_stub)
 112                 return;
 113
 114         ret = init_stub_pte(mm, STUB_CODE,
 115                             (unsigned long) &__syscall_stub_start);
 116         if (ret)
 117                 goto out;
 118
 119         ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
 120         if (ret)
 121                 goto out;
 122
 123         pages = kmalloc(2 * sizeof(struct page *), GFP_KERNEL);
 124         if (pages == NULL) {
 125                 printk(KERN_ERR "arch_dup_mmap failed to allocate 2 page "
 126                        "pointers\n");
 127                 goto out;
 128         }
 129
 130         pages[0] = virt_to_page(&__syscall_stub_start);
 131         pages[1] = virt_to_page(mm->context.id.stack);
 132         mm->context.stub_pages = pages;
 133
 134         /* dup_mmap already holds mmap_sem */
 135         err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
 136                                       VM_READ | VM_MAYREAD | VM_EXEC |
 137                                       VM_MAYEXEC | VM_DONTCOPY, pages);
 138         if (err) {
 139                 printk(KERN_ERR "install_special_mapping returned %d\n", err);
 140                 goto out_free;
 141         }
 142         return;
 143
 144 out_free:
 145         kfree(pages);
 146 out:
 147         force_sigsegv(SIGSEGV, current);
 148 }
 149
 150 void arch_exit_mmap(struct mm_struct *mm)
 151 {
 152         pte_t *pte;
 153
 154         if (mm->context.stub_pages != NULL)
 155                 kfree(mm->context.stub_pages);
 156         pte = virt_to_pte(mm, STUB_CODE);
 157         if (pte != NULL)
 158                 pte_clear(mm, STUB_CODE, pte);
 159
 160         pte = virt_to_pte(mm, STUB_DATA);
 161         if (pte == NULL)
 162                 return;
 163
 164         pte_clear(mm, STUB_DATA, pte);
 165 }
 166
 167 void destroy_context(struct mm_struct *mm)
 168 {
 169         struct mm_context *mmu = &mm->context;
 170
 171         if (proc_mm)
 172                 os_close_file(mmu->id.u.mm_fd);
 173         else {
 174                 /*
 175                  * If init_new_context wasn't called, this will be
 176                  * zero, resulting in a kill(0), which will result in the
 177                  * whole UML suddenly dying.  Also, cover negative and
 178                  * 1 cases, since they shouldn't happen either.
 179                  */
 180                 if (mmu->id.u.pid < 2) {
 181                         printk(KERN_ERR "corrupt mm_context - pid = %d\n",
 182                                mmu->id.u.pid);
 183                         return;
 184                 }
 185                 os_kill_ptraced_process(mmu->id.u.pid, 1);
 186         }
 187
 188         if (skas_needs_stub)
 189                 free_page(mmu->id.stack);
 190
 191         free_ldt(mmu);
 192 }