/* Copyright (C) 2005  David Decotigny
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.
    
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
    
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
    USA. 
 */
 
 #include <hwcore/paging.h>
 #include <sos/thread.h>
 #include <sos/assert.h>
 #include <sos/kmalloc.h>
 
 #include "uaccess.h"
 
 
 int __uaccess_zero_fool_gcc = 0;
 /**
  * Make sure gcc optimizations don't go too far and don't suppress the
  * code at the given label because 1/ a global return is "above" (wrt
  * source code lines), 2/ it is never "goto"
  */
 #define KEEP_LABEL(lbl) \
  ({ if (__uaccess_zero_fool_gcc) goto lbl; })
 
 
 static sos_ret_t nocheck_user_memcpy(sos_vaddr_t dest,
                                      sos_vaddr_t src,
                                      sos_size_t size,
                                      sos_bool_t transfer_from_user)
 {
   __label__ catch_pgflt;
   char *cptr_dst;
   const char *cptr_src;
   sos_size_t transfer_sz;
   sos_ret_t retval;
 
   KEEP_LABEL(catch_pgflt);
 
   retval = sos_thread_prepare_user_space_access(NULL,
                                                 (sos_vaddr_t) && catch_pgflt);
   if (SOS_OK != retval)
     return retval;
 
   /* Version of memcpy that does not alter the stack pointer, in
      order to be able to abruptedly jump to catch_pgflt without stack
      inconsistency. That's the reason why we don't call the normal
      memcpy here: on page fault, it would return back in here, with
      the stack frame returning back here again */
   for (cptr_dst = (char*)dest,
          cptr_src = (const char*)src,
          transfer_sz = size ;
        transfer_sz > 0 ;
        cptr_dst++, cptr_src++, transfer_sz--)
     *cptr_dst = *cptr_src;
 
   retval = sos_thread_end_user_space_access();
   if (SOS_OK != retval)
     return retval;
 
   return size;
 
   /* An unresolved page fault occured while accessing user space */
  catch_pgflt:
   {
     struct sos_thread * cur_thr = sos_thread_get_current();
     sos_uaddr_t faulted_uaddr = cur_thr->fixup_uaccess.faulted_uaddr;
 
     if (transfer_from_user)
       {
         if ( (faulted_uaddr < src) || (faulted_uaddr - size > src) )
           sos_display_fatal_error("Unexpected read access in user space");
         retval = faulted_uaddr - src;
       }
     else
       {
         if ( (faulted_uaddr < dest) || (faulted_uaddr - size > dest) )
           sos_display_fatal_error("Unexpected write access in user space");
         retval = faulted_uaddr - dest;
       }
 
     sos_thread_end_user_space_access();
     return retval;
   }
 }
 
 
 sos_ret_t sos_memcpy_from_user(sos_vaddr_t kernel_to,
                                sos_uaddr_t user_from,
                                sos_size_t size)
 {
   /* Make sure user is trying to access user space */
   if (user_from < SOS_PAGING_BASE_USER_ADDRESS)
     return -SOS_EPERM;
 
   if (user_from > SOS_PAGING_TOP_USER_ADDRESS - size)
     return -SOS_EPERM;
 
   return nocheck_user_memcpy(kernel_to, user_from, size, TRUE);
 }
 
 
 sos_ret_t sos_memcpy_to_user(sos_uaddr_t user_to,
                              sos_vaddr_t kernel_from,
                              sos_size_t size)
 {
   /* Make sure user is trying to access user space */
   if (user_to < SOS_PAGING_BASE_USER_ADDRESS)
     return -SOS_EPERM;
 
   if (user_to > SOS_PAGING_TOP_USER_ADDRESS - size)
     return -SOS_EPERM;
 
   return nocheck_user_memcpy(user_to, kernel_from, size, FALSE);
 }
 
 
 sos_ret_t sos_strnlen_from_user(sos_uaddr_t user_str, sos_size_t max_len)
 {
   __label__ catch_pgflt;
   const char *sc;
   sos_ret_t retval;
 
   KEEP_LABEL(catch_pgflt);
 
   /* Make sure user is trying to access user space */
   if (user_str < SOS_PAGING_BASE_USER_ADDRESS)
     return -SOS_EPERM;
 
   /* Don't allow invalid max_len */
   if ( (max_len < 1) || (max_len > SOS_PAGING_USER_SPACE_SIZE) )
     return -SOS_EINVAL;
 
   retval = sos_thread_prepare_user_space_access(NULL,
                                                 (sos_vaddr_t) && catch_pgflt);
   if (SOS_OK != retval)
     return retval;
 
   /* Version of strnlen that does not alter the stack pointer, in
      order to be able to abruptedly jump to catch_pgflt without stack
      inconsistency. That's the reason why we don't call the normal
      strnlen here: on page fault, it would return back in here, with
      the stack frame returning back here again */
   for (sc = (const char *)user_str; max_len-- && *sc != '\0'; ++sc)
     continue;
 
 
   retval = sos_thread_end_user_space_access();
   if (SOS_OK != retval)
     return retval;
 
   return ((sos_uaddr_t)sc - user_str);
 
   /* An unresolved page fault occured while accessing user space */
  catch_pgflt:
   {
     sos_thread_end_user_space_access();
     return -SOS_EFAULT;
   }
 }
 
 
 static sos_ret_t nocheck_user_strzcpy(char *dst, const char *src,
                                       sos_size_t len)
 {
   __label__ catch_pgflt;
   unsigned int i;
   sos_ret_t retval;
 
   KEEP_LABEL(catch_pgflt);
 
   retval = sos_thread_prepare_user_space_access(NULL,
                                                 (sos_vaddr_t) && catch_pgflt);
   if (SOS_OK != retval)
     return retval;
 
   /* Version of strzcpy that does not alter the stack pointer, in
      order to be able to abruptedly jump to catch_pgflt without stack
      inconsistency. That's the reason why we don't call the normal
      strzcpy here: on page fault, it would return back in here, with
      the stack frame returning back here again */
   for (i = 0; i < len; i++)
     {
       dst[i] = src[i];
       if(src[i] == '\0')
         break;
     }
   
   dst[len-1] = '\0'; 
 
   retval = sos_thread_end_user_space_access();
   if (SOS_OK != retval)
     return retval;
 
   return SOS_OK;
 
   /* An unresolved page fault occured while accessing user space */
  catch_pgflt:
   {
     sos_thread_end_user_space_access();
     return -SOS_EFAULT;
   }
 }
 
 
 sos_ret_t sos_strzcpy_from_user(char *kernel_to, sos_uaddr_t user_from,
                                 sos_size_t max_len)
 {
   /* Make sure user is trying to access user space */
   if ((sos_uaddr_t)user_from < SOS_PAGING_BASE_USER_ADDRESS)
     return -SOS_EPERM;
 
   /* Don't allow invalid max_len */
   if ( (max_len < 1) || (max_len > SOS_PAGING_USER_SPACE_SIZE) )
     return -SOS_EINVAL;
 
   return nocheck_user_strzcpy(kernel_to, (const char*)user_from, max_len);
 }
 
 
 sos_ret_t sos_strzcpy_to_user(sos_uaddr_t user_to, const char *kernel_from,
                               sos_size_t max_len)
 {
   /* Make sure user is trying to access user space */
   if ((sos_uaddr_t)user_to < SOS_PAGING_BASE_USER_ADDRESS)
     return -SOS_EPERM;
 
   /* Don't allow invalid max_len */
   if ( (max_len < 1) || (max_len > SOS_PAGING_USER_SPACE_SIZE) )
     return -SOS_EINVAL;
 
   return nocheck_user_strzcpy((char*)user_to, kernel_from, max_len);
 }
 
 
 sos_ret_t sos_strndup_from_user(char ** kernel_to, sos_uaddr_t from_user,
                                 sos_size_t max_len,
                                 sos_ui32_t kmalloc_flags)
 {
   sos_ret_t retval = sos_strnlen_from_user(from_user, max_len);
   if (retval < 0)
     return retval;
 
   *kernel_to = (char*)sos_kmalloc(retval + 1, kmalloc_flags);
   if (NULL == *kernel_to)
     return -SOS_ENOMEM;
 
   retval = sos_strzcpy_from_user(*kernel_to, from_user, retval + 1);
   if (SOS_OK != retval)
     {
       sos_kfree((sos_vaddr_t)*kernel_to);
       *kernel_to = NULL;
     }
 
   return retval;
 }