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 #include "uaccess.h"
  16
  17 static inline int __handle_fault(struct mm_struct *mm, unsigned long address,
  18                                  int write_access)
  19 {
  20         struct vm_area_struct *vma;
  21         int ret = -EFAULT;
  22
  23         if (in_atomic())
  24                 return ret;
  25         down_read(&mm->mmap_sem);
  26         vma = find_vma(mm, address);
  27         if (unlikely(!vma))
  28                 goto out;
  29         if (unlikely(vma->vm_start > address)) {
  30                 if (!(vma->vm_flags & VM_GROWSDOWN))
  31                         goto out;
  32                 if (expand_stack(vma, address))
  33                         goto out;
  34         }
  35
  36         if (!write_access) {
  37                 /* page not present, check vm flags */
  38                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
  39                         goto out;
  40         } else {
  41                 if (!(vma->vm_flags & VM_WRITE))
  42                         goto out;
  43         }
  44
  45 survive:
  46         switch (handle_mm_fault(mm, vma, address, write_access)) {
  47         case VM_FAULT_MINOR:
  48                 current->min_flt++;
  49                 break;
  50         case VM_FAULT_MAJOR:
  51                 current->maj_flt++;
  52                 break;
  53         case VM_FAULT_SIGBUS:
  54                 goto out_sigbus;
  55         case VM_FAULT_OOM:
  56                 goto out_of_memory;
  57         default:
  58                 BUG();
  59         }
  60         ret = 0;
  61 out:
  62         up_read(&mm->mmap_sem);
  63         return ret;
  64
  65 out_of_memory:
  66         up_read(&mm->mmap_sem);
  67         if (is_init(current)) {
  68                 yield();
  69                 down_read(&mm->mmap_sem);
  70                 goto survive;
  71         }
  72         printk("VM: killing process %s\n", current->comm);
  73         return ret;
  74
  75 out_sigbus:
  76         up_read(&mm->mmap_sem);
  77         current->thread.prot_addr = address;
  78         current->thread.trap_no = 0x11;
  79         force_sig(SIGBUS, current);
  80         return ret;
  81 }
  82
  83 static inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
  84                                     size_t n, int write_user)
  85 {
  86         struct mm_struct *mm = current->mm;
  87         unsigned long offset, pfn, done, size;
  88         pgd_t *pgd;
  89         pmd_t *pmd;
  90         pte_t *pte;
  91         void *from, *to;
  92
  93         done = 0;
  94 retry:
  95         spin_lock(&mm->page_table_lock);
  96         do {
  97                 pgd = pgd_offset(mm, uaddr);
  98                 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
  99                         goto fault;
 100
 101                 pmd = pmd_offset(pgd, uaddr);
 102                 if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
 103                         goto fault;
 104
 105                 pte = pte_offset_map(pmd, uaddr);
 106                 if (!pte || !pte_present(*pte) ||
 107                     (write_user && !pte_write(*pte)))
 108                         goto fault;
 109
 110                 pfn = pte_pfn(*pte);
 111                 if (!pfn_valid(pfn))
 112                         goto out;
 113
 114                 offset = uaddr & (PAGE_SIZE - 1);
 115                 size = min(n - done, PAGE_SIZE - offset);
 116                 if (write_user) {
 117                         to = (void *)((pfn << PAGE_SHIFT) + offset);
 118                         from = kptr + done;
 119                 } else {
 120                         from = (void *)((pfn << PAGE_SHIFT) + offset);
 121                         to = kptr + done;
 122                 }
 123                 memcpy(to, from, size);
 124                 done += size;
 125                 uaddr += size;
 126         } while (done < n);
 127 out:
 128         spin_unlock(&mm->page_table_lock);
 129         return n - done;
 130 fault:
 131         spin_unlock(&mm->page_table_lock);
 132         if (__handle_fault(mm, uaddr, write_user))
 133                 return n - done;
 134         goto retry;
 135 }
 136
 137 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 138 {
 139         size_t rc;
 140
 141         if (segment_eq(get_fs(), KERNEL_DS)) {
 142                 memcpy(to, (void __kernel __force *) from, n);
 143                 return 0;
 144         }
 145         rc = __user_copy_pt((unsigned long) from, to, n, 0);
 146         if (unlikely(rc))
 147                 memset(to + n - rc, 0, rc);
 148         return rc;
 149 }
 150
 151 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 152 {
 153         if (segment_eq(get_fs(), KERNEL_DS)) {
 154                 memcpy((void __kernel __force *) to, from, n);
 155                 return 0;
 156         }
 157         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 158 }