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 <asm/sections.h>
  12 #include <as-layout.h>
  13 #include <os.h>
  14 #include <skas.h>
  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, NULL, 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         stack = get_zeroed_page(GFP_KERNEL);
  57         if (stack == 0)
  58                 goto out;
  59
  60         to_mm->id.stack = stack;
  61         if (current->mm != NULL && current->mm != &init_mm)
  62                 from_mm = &current->mm->context;
  63
  64         if (from_mm)
  65                 to_mm->id.u.pid = copy_context_skas0(stack,
  66                                                      from_mm->id.u.pid);
  67         else to_mm->id.u.pid = start_userspace(stack);
  68
  69         if (to_mm->id.u.pid < 0) {
  70                 ret = to_mm->id.u.pid;
  71                 goto out_free;
  72         }
  73
  74         ret = init_new_ldt(to_mm, from_mm);
  75         if (ret < 0) {
  76                 printk(KERN_ERR "init_new_context_skas - init_ldt"
  77                        " failed, errno = %d\n", ret);
  78                 goto out_free;
  79         }
  80
  81         return 0;
  82
  83  out_free:
  84         if (to_mm->id.stack != 0)
  85                 free_page(to_mm->id.stack);
  86  out:
  87         return ret;
  88 }
  89
  90 void uml_setup_stubs(struct mm_struct *mm)
  91 {
  92         int err, ret;
  93
  94         ret = init_stub_pte(mm, STUB_CODE,
  95                             (unsigned long) __syscall_stub_start);
  96         if (ret)
  97                 goto out;
  98
  99         ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
 100         if (ret)
 101                 goto out;
 102
 103         mm->context.stub_pages[0] = virt_to_page(__syscall_stub_start);
 104         mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
 105
 106         /* dup_mmap already holds mmap_sem */
 107         err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
 108                                       VM_READ | VM_MAYREAD | VM_EXEC |
 109                                       VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP,
 110                                       mm->context.stub_pages);
 111         if (err) {
 112                 printk(KERN_ERR "install_special_mapping returned %d\n", err);
 113                 goto out;
 114         }
 115         return;
 116
 117 out:
 118         force_sigsegv(SIGSEGV, current);
 119 }
 120
 121 void arch_exit_mmap(struct mm_struct *mm)
 122 {
 123         pte_t *pte;
 124
 125         pte = virt_to_pte(mm, STUB_CODE);
 126         if (pte != NULL)
 127                 pte_clear(mm, STUB_CODE, pte);
 128
 129         pte = virt_to_pte(mm, STUB_DATA);
 130         if (pte == NULL)
 131                 return;
 132
 133         pte_clear(mm, STUB_DATA, pte);
 134 }
 135
 136 void destroy_context(struct mm_struct *mm)
 137 {
 138         struct mm_context *mmu = &mm->context;
 139
 140         /*
 141          * If init_new_context wasn't called, this will be
 142          * zero, resulting in a kill(0), which will result in the
 143          * whole UML suddenly dying.  Also, cover negative and
 144          * 1 cases, since they shouldn't happen either.
 145          */
 146         if (mmu->id.u.pid < 2) {
 147                 printk(KERN_ERR "corrupt mm_context - pid = %d\n",
 148                        mmu->id.u.pid);
 149                 return;
 150         }
 151         os_kill_ptraced_process(mmu->id.u.pid, 1);
 152
 153         free_page(mmu->id.stack);
 154         free_ldt(mmu);
 155 }