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 <linux/hardirq.h>
  12 #include <linux/mm.h>
  13 #include <asm/uaccess.h>
  14 #include <asm/futex.h>
  15
  16 static inline int __handle_fault(struct mm_struct *mm, unsigned long address,
  17                                  int write_access)
  18 {
  19         struct vm_area_struct *vma;
  20         int ret = -EFAULT;
  21
  22         if (in_atomic())
  23                 return ret;
  24         down_read(&mm->mmap_sem);
  25         vma = find_vma(mm, address);
  26         if (unlikely(!vma))
  27                 goto out;
  28         if (unlikely(vma->vm_start > address)) {
  29                 if (!(vma->vm_flags & VM_GROWSDOWN))
  30                         goto out;
  31                 if (expand_stack(vma, address))
  32                         goto out;
  33         }
  34
  35         if (!write_access) {
  36                 /* page not present, check vm flags */
  37                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
  38                         goto out;
  39         } else {
  40                 if (!(vma->vm_flags & VM_WRITE))
  41                         goto out;
  42         }
  43
  44 survive:
  45         switch (handle_mm_fault(mm, vma, address, write_access)) {
  46         case VM_FAULT_MINOR:
  47                 current->min_flt++;
  48                 break;
  49         case VM_FAULT_MAJOR:
  50                 current->maj_flt++;
  51                 break;
  52         case VM_FAULT_SIGBUS:
  53                 goto out_sigbus;
  54         case VM_FAULT_OOM:
  55                 goto out_of_memory;
  56         default:
  57                 BUG();
  58         }
  59         ret = 0;
  60 out:
  61         up_read(&mm->mmap_sem);
  62         return ret;
  63
  64 out_of_memory:
  65         up_read(&mm->mmap_sem);
  66         if (is_init(current)) {
  67                 yield();
  68                 down_read(&mm->mmap_sem);
  69                 goto survive;
  70         }
  71         printk("VM: killing process %s\n", current->comm);
  72         return ret;
  73
  74 out_sigbus:
  75         up_read(&mm->mmap_sem);
  76         current->thread.prot_addr = address;
  77         current->thread.trap_no = 0x11;
  78         force_sig(SIGBUS, current);
  79         return ret;
  80 }
  81
  82 static inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
  83                                     size_t n, int write_user)
  84 {
  85         struct mm_struct *mm = current->mm;
  86         unsigned long offset, pfn, done, size;
  87         pgd_t *pgd;
  88         pmd_t *pmd;
  89         pte_t *pte;
  90         void *from, *to;
  91
  92         done = 0;
  93 retry:
  94         spin_lock(&mm->page_table_lock);
  95         do {
  96                 pgd = pgd_offset(mm, uaddr);
  97                 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
  98                         goto fault;
  99
 100                 pmd = pmd_offset(pgd, uaddr);
 101                 if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
 102                         goto fault;
 103
 104                 pte = pte_offset_map(pmd, uaddr);
 105                 if (!pte || !pte_present(*pte) ||
 106                     (write_user && !pte_write(*pte)))
 107                         goto fault;
 108
 109                 pfn = pte_pfn(*pte);
 110                 if (!pfn_valid(pfn))
 111                         goto out;
 112
 113                 offset = uaddr & (PAGE_SIZE - 1);
 114                 size = min(n - done, PAGE_SIZE - offset);
 115                 if (write_user) {
 116                         to = (void *)((pfn << PAGE_SHIFT) + offset);
 117                         from = kptr + done;
 118                 } else {
 119                         from = (void *)((pfn << PAGE_SHIFT) + offset);
 120                         to = kptr + done;
 121                 }
 122                 memcpy(to, from, size);
 123                 done += size;
 124                 uaddr += size;
 125         } while (done < n);
 126 out:
 127         spin_unlock(&mm->page_table_lock);
 128         return n - done;
 129 fault:
 130         spin_unlock(&mm->page_table_lock);
 131         if (__handle_fault(mm, uaddr, write_user))
 132                 return n - done;
 133         goto retry;
 134 }
 135
 136 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 137 {
 138         size_t rc;
 139
 140         if (segment_eq(get_fs(), KERNEL_DS)) {
 141                 memcpy(to, (void __kernel __force *) from, n);
 142                 return 0;
 143         }
 144         rc = __user_copy_pt((unsigned long) from, to, n, 0);
 145         if (unlikely(rc))
 146                 memset(to + n - rc, 0, rc);
 147         return rc;
 148 }
 149
 150 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 151 {
 152         if (segment_eq(get_fs(), KERNEL_DS)) {
 153                 memcpy((void __kernel __force *) to, from, n);
 154                 return 0;
 155         }
 156         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 157 }