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
  14 extern int __syscall_stub_start;
  15
  16 static 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
  49 int 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
 105 void 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
 143 out_free:
 144         kfree(pages);
 145 out:
 146         force_sigsegv(SIGSEGV, current);
 147 }
 148
 149 void 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
 166 void 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 }