linux-user/uaccess.c

   1 /* User memory access */
   2 #include "qemu/osdep.h"
   3 #include "qemu/cutils.h"
   4
   5 #include "qemu.h"
   6 #include "user-internals.h"
   7
   8 void *lock_user(int type, abi_ulong guest_addr, ssize_t len, bool copy)
   9 {
  10     void *host_addr;
  11
  12     guest_addr = cpu_untagged_addr(thread_cpu, guest_addr);
  13     if (!access_ok_untagged(type, guest_addr, len)) {
  14         return NULL;
  15     }
  16     host_addr = g2h_untagged(guest_addr);
  17 #ifdef CONFIG_DEBUG_REMAP
  18     if (copy) {
  19         host_addr = g_memdup(host_addr, len);
  20     } else {
  21         host_addr = g_malloc0(len);
  22     }
  23 #endif
  24     return host_addr;
  25 }
  26
  27 #ifdef CONFIG_DEBUG_REMAP
  28 void unlock_user(void *host_ptr, abi_ulong guest_addr, ssize_t len)
  29 {
  30     void *host_ptr_conv;
  31
  32     if (!host_ptr) {
  33         return;
  34     }
  35     host_ptr_conv = g2h(thread_cpu, guest_addr);
  36     if (host_ptr == host_ptr_conv) {
  37         return;
  38     }
  39     if (len > 0) {
  40         memcpy(host_ptr_conv, host_ptr, len);
  41     }
  42     g_free(host_ptr);
  43 }
  44 #endif
  45
  46 void *lock_user_string(abi_ulong guest_addr)
  47 {
  48     ssize_t len = target_strlen(guest_addr);
  49     if (len < 0) {
  50         return NULL;
  51     }
  52     return lock_user(VERIFY_READ, guest_addr, len + 1, 1);
  53 }
  54
  55 /* copy_from_user() and copy_to_user() are usually used to copy data
  56  * buffers between the target and host.  These internally perform
  57  * locking/unlocking of the memory.
  58  */
  59 int copy_from_user(void *hptr, abi_ulong gaddr, ssize_t len)
  60 {
  61     int ret = 0;
  62     void *ghptr = lock_user(VERIFY_READ, gaddr, len, 1);
  63
  64     if (ghptr) {
  65         memcpy(hptr, ghptr, len);
  66         unlock_user(ghptr, gaddr, 0);
  67     } else {
  68         ret = -TARGET_EFAULT;
  69     }
  70     return ret;
  71 }
  72
  73 int copy_to_user(abi_ulong gaddr, void *hptr, ssize_t len)
  74 {
  75     int ret = 0;
  76     void *ghptr = lock_user(VERIFY_WRITE, gaddr, len, 0);
  77
  78     if (ghptr) {
  79         memcpy(ghptr, hptr, len);
  80         unlock_user(ghptr, gaddr, len);
  81     } else {
  82         ret = -TARGET_EFAULT;
  83     }
  84
  85     return ret;
  86 }
  87
  88 /* Return the length of a string in target memory or -TARGET_EFAULT if
  89    access error  */
  90 ssize_t target_strlen(abi_ulong guest_addr1)
  91 {
  92     uint8_t *ptr;
  93     abi_ulong guest_addr;
  94     size_t max_len, len;
  95
  96     guest_addr = guest_addr1;
  97     for(;;) {
  98         max_len = TARGET_PAGE_SIZE - (guest_addr & ~TARGET_PAGE_MASK);
  99         ptr = lock_user(VERIFY_READ, guest_addr, max_len, 1);
 100         if (!ptr)
 101             return -TARGET_EFAULT;
 102         len = qemu_strnlen((const char *)ptr, max_len);
 103         unlock_user(ptr, guest_addr, 0);
 104         guest_addr += len;
 105         /* we don't allow wrapping or integer overflow */
 106         if (guest_addr == 0 || (guest_addr - guest_addr1) > 0x7fffffff) {
 107             return -TARGET_EFAULT;
 108         }
 109         if (len != max_len) {
 110             break;
 111         }
 112     }
 113     return guest_addr - guest_addr1;
 114 }