arch/s390/lib/uaccess_pt.c

   1 /*
   2  *  User access functions based on page table walks for enhanced
   3  *  system layout without hardware support.
   4  *
   5  *    Copyright IBM Corp. 2006, 2012
   6  *    Author(s): Gerald Schaefer (gerald.schaefer@de.ibm.com)
   7  */
   8
   9 #include <linux/errno.h>
  10 #include <linux/hardirq.h>
  11 #include <linux/mm.h>
  12 #include <linux/hugetlb.h>
  13 #include <asm/uaccess.h>
  14 #include <asm/futex.h>
  15 #include "uaccess.h"
  16
  17
  18 /*
  19  * Returns kernel address for user virtual address. If the returned address is
  20  * >= -4095 (IS_ERR_VALUE(x) returns true), a fault has occured and the address
  21  * contains the (negative) exception code.
  22  */
  23 static __always_inline unsigned long follow_table(struct mm_struct *mm,
  24                                                   unsigned long addr, int write)
  25 {
  26         pgd_t *pgd;
  27         pud_t *pud;
  28         pmd_t *pmd;
  29         pte_t *ptep;
  30
  31         pgd = pgd_offset(mm, addr);
  32         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
  33                 return -0x3aUL;
  34
  35         pud = pud_offset(pgd, addr);
  36         if (pud_none(*pud) || unlikely(pud_bad(*pud)))
  37                 return -0x3bUL;
  38
  39         pmd = pmd_offset(pud, addr);
  40         if (pmd_none(*pmd))
  41                 return -0x10UL;
  42         if (pmd_large(*pmd)) {
  43                 if (write && (pmd_val(*pmd) & _SEGMENT_ENTRY_RO))
  44                         return -0x04UL;
  45                 return (pmd_val(*pmd) & HPAGE_MASK) + (addr & ~HPAGE_MASK);
  46         }
  47         if (unlikely(pmd_bad(*pmd)))
  48                 return -0x10UL;
  49
  50         ptep = pte_offset_map(pmd, addr);
  51         if (!pte_present(*ptep))
  52                 return -0x11UL;
  53         if (write && !pte_write(*ptep))
  54                 return -0x04UL;
  55
  56         return (pte_val(*ptep) & PAGE_MASK) + (addr & ~PAGE_MASK);
  57 }
  58
  59 static __always_inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
  60                                              size_t n, int write_user)
  61 {
  62         struct mm_struct *mm = current->mm;
  63         unsigned long offset, done, size, kaddr;
  64         void *from, *to;
  65
  66         done = 0;
  67 retry:
  68         spin_lock(&mm->page_table_lock);
  69         do {
  70                 kaddr = follow_table(mm, uaddr, write_user);
  71                 if (IS_ERR_VALUE(kaddr))
  72                         goto fault;
  73
  74                 offset = uaddr & ~PAGE_MASK;
  75                 size = min(n - done, PAGE_SIZE - offset);
  76                 if (write_user) {
  77                         to = (void *) kaddr;
  78                         from = kptr + done;
  79                 } else {
  80                         from = (void *) kaddr;
  81                         to = kptr + done;
  82                 }
  83                 memcpy(to, from, size);
  84                 done += size;
  85                 uaddr += size;
  86         } while (done < n);
  87         spin_unlock(&mm->page_table_lock);
  88         return n - done;
  89 fault:
  90         spin_unlock(&mm->page_table_lock);
  91         if (__handle_fault(uaddr, -kaddr, write_user))
  92                 return n - done;
  93         goto retry;
  94 }
  95
  96 /*
  97  * Do DAT for user address by page table walk, return kernel address.
  98  * This function needs to be called with current->mm->page_table_lock held.
  99  */
 100 static __always_inline unsigned long __dat_user_addr(unsigned long uaddr,
 101                                                      int write)
 102 {
 103         struct mm_struct *mm = current->mm;
 104         unsigned long kaddr;
 105         int rc;
 106
 107 retry:
 108         kaddr = follow_table(mm, uaddr, write);
 109         if (IS_ERR_VALUE(kaddr))
 110                 goto fault;
 111
 112         return kaddr;
 113 fault:
 114         spin_unlock(&mm->page_table_lock);
 115         rc = __handle_fault(uaddr, -kaddr, write);
 116         spin_lock(&mm->page_table_lock);
 117         if (!rc)
 118                 goto retry;
 119         return 0;
 120 }
 121
 122 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 123 {
 124         size_t rc;
 125
 126         if (segment_eq(get_fs(), KERNEL_DS)) {
 127                 memcpy(to, (void __kernel __force *) from, n);
 128                 return 0;
 129         }
 130         rc = __user_copy_pt((unsigned long) from, to, n, 0);
 131         if (unlikely(rc))
 132                 memset(to + n - rc, 0, rc);
 133         return rc;
 134 }
 135
 136 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 137 {
 138         if (segment_eq(get_fs(), KERNEL_DS)) {
 139                 memcpy((void __kernel __force *) to, from, n);
 140                 return 0;
 141         }
 142         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 143 }
 144
 145 static size_t clear_user_pt(size_t n, void __user *to)
 146 {
 147         long done, size, ret;
 148
 149         if (segment_eq(get_fs(), KERNEL_DS)) {
 150                 memset((void __kernel __force *) to, 0, n);
 151                 return 0;
 152         }
 153         done = 0;
 154         do {
 155                 if (n - done > PAGE_SIZE)
 156                         size = PAGE_SIZE;
 157                 else
 158                         size = n - done;
 159                 ret = __user_copy_pt((unsigned long) to + done,
 160                                       &empty_zero_page, size, 1);
 161                 done += size;
 162                 if (ret)
 163                         return ret + n - done;
 164         } while (done < n);
 165         return 0;
 166 }
 167
 168 static size_t strnlen_user_pt(size_t count, const char __user *src)
 169 {
 170         unsigned long uaddr = (unsigned long) src;
 171         struct mm_struct *mm = current->mm;
 172         unsigned long offset, done, len, kaddr;
 173         size_t len_str;
 174
 175         if (segment_eq(get_fs(), KERNEL_DS))
 176                 return strnlen((const char __kernel __force *) src, count) + 1;
 177         done = 0;
 178 retry:
 179         spin_lock(&mm->page_table_lock);
 180         do {
 181                 kaddr = follow_table(mm, uaddr, 0);
 182                 if (IS_ERR_VALUE(kaddr))
 183                         goto fault;
 184
 185                 offset = uaddr & ~PAGE_MASK;
 186                 len = min(count - done, PAGE_SIZE - offset);
 187                 len_str = strnlen((char *) kaddr, len);
 188                 done += len_str;
 189                 uaddr += len_str;
 190         } while ((len_str == len) && (done < count));
 191         spin_unlock(&mm->page_table_lock);
 192         return done + 1;
 193 fault:
 194         spin_unlock(&mm->page_table_lock);
 195         if (__handle_fault(uaddr, -kaddr, 0))
 196                 return 0;
 197         goto retry;
 198 }
 199
 200 static size_t strncpy_from_user_pt(size_t count, const char __user *src,
 201                                    char *dst)
 202 {
 203         size_t n = strnlen_user_pt(count, src);
 204
 205         if (!n)
 206                 return -EFAULT;
 207         if (n > count)
 208                 n = count;
 209         if (segment_eq(get_fs(), KERNEL_DS)) {
 210                 memcpy(dst, (const char __kernel __force *) src, n);
 211                 if (dst[n-1] == '\0')
 212                         return n-1;
 213                 else
 214                         return n;
 215         }
 216         if (__user_copy_pt((unsigned long) src, dst, n, 0))
 217                 return -EFAULT;
 218         if (dst[n-1] == '\0')
 219                 return n-1;
 220         else
 221                 return n;
 222 }
 223
 224 static size_t copy_in_user_pt(size_t n, void __user *to,
 225                               const void __user *from)
 226 {
 227         struct mm_struct *mm = current->mm;
 228         unsigned long offset_max, uaddr, done, size, error_code;
 229         unsigned long uaddr_from = (unsigned long) from;
 230         unsigned long uaddr_to = (unsigned long) to;
 231         unsigned long kaddr_to, kaddr_from;
 232         int write_user;
 233
 234         if (segment_eq(get_fs(), KERNEL_DS)) {
 235                 memcpy((void __force *) to, (void __force *) from, n);
 236                 return 0;
 237         }
 238         done = 0;
 239 retry:
 240         spin_lock(&mm->page_table_lock);
 241         do {
 242                 write_user = 0;
 243                 uaddr = uaddr_from;
 244                 kaddr_from = follow_table(mm, uaddr_from, 0);
 245                 error_code = kaddr_from;
 246                 if (IS_ERR_VALUE(error_code))
 247                         goto fault;
 248
 249                 write_user = 1;
 250                 uaddr = uaddr_to;
 251                 kaddr_to = follow_table(mm, uaddr_to, 1);
 252                 error_code = (unsigned long) kaddr_to;
 253                 if (IS_ERR_VALUE(error_code))
 254                         goto fault;
 255
 256                 offset_max = max(uaddr_from & ~PAGE_MASK,
 257                                  uaddr_to & ~PAGE_MASK);
 258                 size = min(n - done, PAGE_SIZE - offset_max);
 259
 260                 memcpy((void *) kaddr_to, (void *) kaddr_from, size);
 261                 done += size;
 262                 uaddr_from += size;
 263                 uaddr_to += size;
 264         } while (done < n);
 265         spin_unlock(&mm->page_table_lock);
 266         return n - done;
 267 fault:
 268         spin_unlock(&mm->page_table_lock);
 269         if (__handle_fault(uaddr, -error_code, write_user))
 270                 return n - done;
 271         goto retry;
 272 }
 273
 274 #define __futex_atomic_op(insn, ret, oldval, newval, uaddr, oparg)      \
 275         asm volatile("0: l   %1,0(%6)\n"                                \
 276                      "1: " insn                                         \
 277                      "2: cs  %1,%2,0(%6)\n"                             \
 278                      "3: jl  1b\n"                                      \
 279                      "   lhi %0,0\n"                                    \
 280                      "4:\n"                                             \
 281                      EX_TABLE(0b,4b) EX_TABLE(2b,4b) EX_TABLE(3b,4b)    \
 282                      : "=d" (ret), "=&d" (oldval), "=&d" (newval),      \
 283                        "=m" (*uaddr)                                    \
 284                      : "0" (-EFAULT), "d" (oparg), "a" (uaddr),         \
 285                        "m" (*uaddr) : "cc" );
 286
 287 static int __futex_atomic_op_pt(int op, u32 __user *uaddr, int oparg, int *old)
 288 {
 289         int oldval = 0, newval, ret;
 290
 291         switch (op) {
 292         case FUTEX_OP_SET:
 293                 __futex_atomic_op("lr %2,%5\n",
 294                                   ret, oldval, newval, uaddr, oparg);
 295                 break;
 296         case FUTEX_OP_ADD:
 297                 __futex_atomic_op("lr %2,%1\nar %2,%5\n",
 298                                   ret, oldval, newval, uaddr, oparg);
 299                 break;
 300         case FUTEX_OP_OR:
 301                 __futex_atomic_op("lr %2,%1\nor %2,%5\n",
 302                                   ret, oldval, newval, uaddr, oparg);
 303                 break;
 304         case FUTEX_OP_ANDN:
 305                 __futex_atomic_op("lr %2,%1\nnr %2,%5\n",
 306                                   ret, oldval, newval, uaddr, oparg);
 307                 break;
 308         case FUTEX_OP_XOR:
 309                 __futex_atomic_op("lr %2,%1\nxr %2,%5\n",
 310                                   ret, oldval, newval, uaddr, oparg);
 311                 break;
 312         default:
 313                 ret = -ENOSYS;
 314         }
 315         if (ret == 0)
 316                 *old = oldval;
 317         return ret;
 318 }
 319
 320 int futex_atomic_op_pt(int op, u32 __user *uaddr, int oparg, int *old)
 321 {
 322         int ret;
 323
 324         if (segment_eq(get_fs(), KERNEL_DS))
 325                 return __futex_atomic_op_pt(op, uaddr, oparg, old);
 326         spin_lock(&current->mm->page_table_lock);
 327         uaddr = (u32 __force __user *)
 328                 __dat_user_addr((__force unsigned long) uaddr, 1);
 329         if (!uaddr) {
 330                 spin_unlock(&current->mm->page_table_lock);
 331                 return -EFAULT;
 332         }
 333         get_page(virt_to_page(uaddr));
 334         spin_unlock(&current->mm->page_table_lock);
 335         ret = __futex_atomic_op_pt(op, uaddr, oparg, old);
 336         put_page(virt_to_page(uaddr));
 337         return ret;
 338 }
 339
 340 static int __futex_atomic_cmpxchg_pt(u32 *uval, u32 __user *uaddr,
 341                                      u32 oldval, u32 newval)
 342 {
 343         int ret;
 344
 345         asm volatile("0: cs   %1,%4,0(%5)\n"
 346                      "1: la   %0,0\n"
 347                      "2:\n"
 348                      EX_TABLE(0b,2b) EX_TABLE(1b,2b)
 349                      : "=d" (ret), "+d" (oldval), "=m" (*uaddr)
 350                      : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
 351                      : "cc", "memory" );
 352         *uval = oldval;
 353         return ret;
 354 }
 355
 356 int futex_atomic_cmpxchg_pt(u32 *uval, u32 __user *uaddr,
 357                             u32 oldval, u32 newval)
 358 {
 359         int ret;
 360
 361         if (segment_eq(get_fs(), KERNEL_DS))
 362                 return __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 363         spin_lock(&current->mm->page_table_lock);
 364         uaddr = (u32 __force __user *)
 365                 __dat_user_addr((__force unsigned long) uaddr, 1);
 366         if (!uaddr) {
 367                 spin_unlock(&current->mm->page_table_lock);
 368                 return -EFAULT;
 369         }
 370         get_page(virt_to_page(uaddr));
 371         spin_unlock(&current->mm->page_table_lock);
 372         ret = __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 373         put_page(virt_to_page(uaddr));
 374         return ret;
 375 }
 376
 377 struct uaccess_ops uaccess_pt = {
 378         .copy_from_user         = copy_from_user_pt,
 379         .copy_from_user_small   = copy_from_user_pt,
 380         .copy_to_user           = copy_to_user_pt,
 381         .copy_to_user_small     = copy_to_user_pt,
 382         .copy_in_user           = copy_in_user_pt,
 383         .clear_user             = clear_user_pt,
 384         .strnlen_user           = strnlen_user_pt,
 385         .strncpy_from_user      = strncpy_from_user_pt,
 386         .futex_atomic_op        = futex_atomic_op_pt,
 387         .futex_atomic_cmpxchg   = futex_atomic_cmpxchg_pt,
 388 };