linux-user/uaccess.c

   1 /* User memory access */
   2 #include <stdio.h>
   3 #include <string.h>
   4
   5 #include "qemu.h"
   6
   7 /* copy_from_user() and copy_to_user() are usually used to copy data
   8  * buffers between the target and host.  These internally perform
   9  * locking/unlocking of the memory.
  10  */
  11 abi_long copy_from_user(void *hptr, abi_ulong gaddr, size_t len)
  12 {
  13     abi_long ret = 0;
  14     void *ghptr;
  15
  16     if ((ghptr = lock_user(VERIFY_READ, gaddr, len, 1))) {
  17         memcpy(hptr, ghptr, len);
  18         unlock_user(ghptr, gaddr, 0);
  19     } else
  20         ret = -TARGET_EFAULT;
  21
  22     return ret;
  23 }
  24
  25
  26 abi_long copy_to_user(abi_ulong gaddr, void *hptr, size_t len)
  27 {
  28     abi_long ret = 0;
  29     void *ghptr;
  30
  31     if ((ghptr = lock_user(VERIFY_WRITE, gaddr, len, 0))) {
  32         memcpy(ghptr, hptr, len);
  33         unlock_user(ghptr, gaddr, len);
  34     } else
  35         ret = -TARGET_EFAULT;
  36
  37     return ret;
  38 }
  39
  40 /* XXX: use host strnlen if available ? */
  41 static int qemu_strnlen(const char *s, int max_len)
  42 {
  43     int i;
  44     for(i = 0; i < max_len; i++) {
  45         if (s[i] == '\0')
  46             break;
  47     }
  48     return i;
  49 }
  50
  51 /* Return the length of a string in target memory or -TARGET_EFAULT if
  52    access error  */
  53 abi_long target_strlen(abi_ulong guest_addr1)
  54 {
  55     uint8_t *ptr;
  56     abi_ulong guest_addr;
  57     int max_len, len;
  58
  59     guest_addr = guest_addr1;
  60     for(;;) {
  61         max_len = TARGET_PAGE_SIZE - (guest_addr & ~TARGET_PAGE_MASK);
  62         ptr = lock_user(VERIFY_READ, guest_addr, max_len, 1);
  63         if (!ptr)
  64             return -TARGET_EFAULT;
  65         len = qemu_strnlen(ptr, max_len);
  66         unlock_user(ptr, guest_addr, 0);
  67         guest_addr += len;
  68         /* we don't allow wrapping or integer overflow */
  69         if (guest_addr == 0 ||
  70             (guest_addr - guest_addr1) > 0x7fffffff)
  71             return -TARGET_EFAULT;
  72         if (len != max_len)
  73             break;
  74     }
  75     return guest_addr - guest_addr1;
  76 }