arch/s390/lib/uaccess_pt.c

   1 /*
   2  *  arch/s390/lib/uaccess_pt.c
   3  *
   4  *  User access functions based on page table walks.
   5  *
   6  *    Copyright IBM Corp. 2006
   7  *    Author(s): Gerald Schaefer (gerald.schaefer@de.ibm.com)
   8  */
   9
  10 #include <linux/errno.h>
  11 #include <asm/uaccess.h>
  12 #include <linux/mm.h>
  13 #include <asm/futex.h>
  14
  15 static inline int __handle_fault(struct mm_struct *mm, unsigned long address,
  16                                  int write_access)
  17 {
  18         struct vm_area_struct *vma;
  19         int ret = -EFAULT;
  20
  21         down_read(&mm->mmap_sem);
  22         vma = find_vma(mm, address);
  23         if (unlikely(!vma))
  24                 goto out;
  25         if (unlikely(vma->vm_start > address)) {
  26                 if (!(vma->vm_flags & VM_GROWSDOWN))
  27                         goto out;
  28                 if (expand_stack(vma, address))
  29                         goto out;
  30         }
  31
  32         if (!write_access) {
  33                 /* page not present, check vm flags */
  34                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
  35                         goto out;
  36         } else {
  37                 if (!(vma->vm_flags & VM_WRITE))
  38                         goto out;
  39         }
  40
  41 survive:
  42         switch (handle_mm_fault(mm, vma, address, write_access)) {
  43         case VM_FAULT_MINOR:
  44                 current->min_flt++;
  45                 break;
  46         case VM_FAULT_MAJOR:
  47                 current->maj_flt++;
  48                 break;
  49         case VM_FAULT_SIGBUS:
  50                 goto out_sigbus;
  51         case VM_FAULT_OOM:
  52                 goto out_of_memory;
  53         default:
  54                 BUG();
  55         }
  56         ret = 0;
  57 out:
  58         up_read(&mm->mmap_sem);
  59         return ret;
  60
  61 out_of_memory:
  62         up_read(&mm->mmap_sem);
  63         if (current->pid == 1) {
  64                 yield();
  65                 goto survive;
  66         }
  67         printk("VM: killing process %s\n", current->comm);
  68         return ret;
  69
  70 out_sigbus:
  71         up_read(&mm->mmap_sem);
  72         current->thread.prot_addr = address;
  73         current->thread.trap_no = 0x11;
  74         force_sig(SIGBUS, current);
  75         return ret;
  76 }
  77
  78 static inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
  79                                     size_t n, int write_user)
  80 {
  81         struct mm_struct *mm = current->mm;
  82         unsigned long offset, pfn, done, size;
  83         pgd_t *pgd;
  84         pmd_t *pmd;
  85         pte_t *pte;
  86         void *from, *to;
  87
  88         done = 0;
  89 retry:
  90         spin_lock(&mm->page_table_lock);
  91         do {
  92                 pgd = pgd_offset(mm, uaddr);
  93                 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
  94                         goto fault;
  95
  96                 pmd = pmd_offset(pgd, uaddr);
  97                 if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
  98                         goto fault;
  99
 100                 pte = pte_offset_map(pmd, uaddr);
 101                 if (!pte || !pte_present(*pte) ||
 102                     (write_user && !pte_write(*pte)))
 103                         goto fault;
 104
 105                 pfn = pte_pfn(*pte);
 106                 if (!pfn_valid(pfn))
 107                         goto out;
 108
 109                 offset = uaddr & (PAGE_SIZE - 1);
 110                 size = min(n - done, PAGE_SIZE - offset);
 111                 if (write_user) {
 112                         to = (void *)((pfn << PAGE_SHIFT) + offset);
 113                         from = kptr + done;
 114                 } else {
 115                         from = (void *)((pfn << PAGE_SHIFT) + offset);
 116                         to = kptr + done;
 117                 }
 118                 memcpy(to, from, size);
 119                 done += size;
 120                 uaddr += size;
 121         } while (done < n);
 122 out:
 123         spin_unlock(&mm->page_table_lock);
 124         return n - done;
 125 fault:
 126         spin_unlock(&mm->page_table_lock);
 127         if (__handle_fault(mm, uaddr, write_user))
 128                 return n - done;
 129         goto retry;
 130 }
 131
 132 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 133 {
 134         size_t rc;
 135
 136         if (segment_eq(get_fs(), KERNEL_DS)) {
 137                 memcpy(to, (void __kernel __force *) from, n);
 138                 return 0;
 139         }
 140         rc = __user_copy_pt((unsigned long) from, to, n, 0);
 141         if (unlikely(rc))
 142                 memset(to + n - rc, 0, rc);
 143         return rc;
 144 }
 145
 146 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 147 {
 148         if (segment_eq(get_fs(), KERNEL_DS)) {
 149                 memcpy((void __kernel __force *) to, from, n);
 150                 return 0;
 151         }
 152         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 153 }