/* Copyright (C) 2005,2006 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 <sos/assert.h>
 #include <sos/list.h>
 #include <sos/physmem.h>
 #include <sos/kmem_slab.h>
 #include <drivers/bochs.h>
 #include <hwcore/mm_context.h>
 #include <hwcore/paging.h>
 #include <drivers/zero.h>
 
 #include "umem_vmm.h"
 
 
 struct sos_umem_vmm_as
 {
   /** The process that owns this address space */
   struct sos_process     * process;
 
   /** The MMU configuration of this address space */
   struct sos_mm_context  * mm_context;
 
   /** The list of VRs in this address space */
   struct sos_umem_vmm_vr * list_vr;
 
   /** Heap location */
   sos_uaddr_t heap_start;
   sos_size_t  heap_size; /**< Updated by sos_umem_vmm_brk() */
 
   /* Memory usage statistics */
   sos_size_t phys_total; /* shared + private */
   struct vm_usage
   {
     sos_size_t overall;
     sos_size_t ro, rw, code /* all: non readable, read and read/write */;
   } vm_total, vm_shrd;
 
   /* Page fault counters */
   sos_size_t pgflt_cow;
   sos_size_t pgflt_page_in;
   sos_size_t pgflt_invalid;
 };
 
 
 struct sos_umem_vmm_vr
 {
   /** The address space owning this VR */
   struct sos_umem_vmm_as *address_space;
 
   /** The location of the mapping in user space */
   sos_uaddr_t start;
   sos_size_t  size;
 
   /** What accesses are allowed (read, write, exec): @see
       SOS_VM_MAP_PROT_* flags in hwcore/paging.h */
   sos_ui32_t  access_rights;
 
   /** Flags of the VR. Allowed flags:
    *  - SOS_VR_MAP_SHARED
    */
   sos_ui32_t  flags;
 
   /**
    * The callbacks for the VR called along map/unmapping of the
    * resource
    */
   struct sos_umem_vmm_vr_ops *ops;
 
   /** Description of the resource being mapped, if any */
   struct sos_umem_vmm_mapped_resource *mapped_resource;
   sos_luoffset_t offset_in_resource;
 
   /** The VRs of an AS are linked together and are accessible by way
       of as->list_vr */
   struct sos_umem_vmm_vr *prev_in_as, *next_in_as;
 
   /** The VRs mapping a given resource are linked together and are
       accessible by way of mapped_resource->list_vr */
   struct sos_umem_vmm_vr *prev_in_mapped_resource, *next_in_mapped_resource;
 };
 
 
 /*
  * We use special slab caches to allocate AS and VR data structures
  */
 static struct sos_kslab_cache * cache_of_as;
 static struct sos_kslab_cache * cache_of_vr;
 
 
 /** Temporary function to debug: list the VRs of the given As */
 void sos_dump_as(const struct sos_umem_vmm_as * as, const char *str)
 {
   struct sos_umem_vmm_vr *vr;
   int nb_vr;
 
   sos_bochs_printf("AS %p - %s:\n", as, str);
   sos_bochs_printf("   physical mem: %x\n",
                    as->phys_total);
   sos_bochs_printf("   VM (all/ro+rw/exec) tot:%x/%x+%x/%x shrd:%x/%x+%x/%x\n",
                    as->vm_total.overall,
                    as->vm_total.ro, as->vm_total.rw, as->vm_total.code,
                    as->vm_shrd.overall,
                    as->vm_shrd.ro, as->vm_shrd.rw, as->vm_shrd.code);
   sos_bochs_printf("   pgflt cow=%d pgin=%d inv=%d\n",
                    as->pgflt_cow, as->pgflt_page_in, as->pgflt_invalid);
   list_foreach_named(as->list_vr, vr, nb_vr, prev_in_as, next_in_as)
     {
       sos_bochs_printf("  VR[%d]=%x: [%x,%x[ (sz=%x) mr=(%x)+%llx %c%c%c fl=%x\n",
                        nb_vr, (unsigned)vr,
                        vr->start, vr->start + vr->size, vr->size,
                        (unsigned)vr->mapped_resource,
                        vr->offset_in_resource,
                        (vr->access_rights & SOS_VM_MAP_PROT_READ)?'r':'-',
                        (vr->access_rights & SOS_VM_MAP_PROT_WRITE)?'w':'-',
                        (vr->access_rights & SOS_VM_MAP_PROT_EXEC)?'x':'-',
                        (unsigned)vr->flags);
     }
   sos_bochs_printf("FIN (%s)\n", str);
 }
 
 
 /**
  * Physical address of THE page (full of 0s) used for anonymous
  * mappings
  */
 sos_paddr_t sos_zero_physpage = 0 /* Initial value prior to allocation */;
 sos_vaddr_t sos_zero_kernelpage = 0 /* Initial value prior to allocation */;
 
 
 /*
  * Helper functions defined at the bottom of the file
  */
 
 /**
  * Helper function to retrieve the first VR to have a vr->end >= uaddr
  */
 static struct sos_umem_vmm_vr *
 find_enclosing_or_next_vr(struct sos_umem_vmm_as * as,
                           sos_uaddr_t uaddr);
 
 
 /**
  * Helper function to retrieve the first VR that overlaps the given
  * interval, if any
  */
 static struct sos_umem_vmm_vr *
 find_first_intersecting_vr(struct sos_umem_vmm_as * as,
                            sos_uaddr_t start_uaddr, sos_size_t size);
 
 
 /**
  * Helper function to find first address where there is enough
  * space. Begin to look for such an interval at or after the given
  * address
  *
  * @param hint_addr The address where to begin the scan, or NULL
  */
 static sos_uaddr_t
 find_first_free_interval(struct sos_umem_vmm_as * as,
                          sos_uaddr_t hint_uaddr, sos_size_t size);
 
 
 /** Called each time a VR of the AS changes. Don't cope with any
     underlying physcal mapping/unmapping, COW, etc... */
 static void
 as_account_change_of_vr_protection(struct sos_umem_vmm_as * as,
                                    sos_bool_t is_shared,
                                    sos_size_t size,
                                    sos_ui32_t prev_access_rights,
                                    sos_ui32_t new_access_rights);
 
 
 sos_ret_t sos_umem_vmm_subsystem_setup()
 {
   /* Allocate a new kernel physical page mapped into kernel space and
      reset it with 0s */
   sos_zero_kernelpage = sos_kmem_vmm_alloc(1, SOS_KMEM_VMM_MAP);
   if (sos_zero_kernelpage == (sos_vaddr_t)NULL)
     return -SOS_ENOMEM;
   memset((void*)sos_zero_kernelpage, 0x0, SOS_PAGE_SIZE);
   
   /* Keep a reference to the underlying pphysical page... */
   sos_zero_physpage = sos_paging_get_paddr(sos_zero_kernelpage);
   SOS_ASSERT_FATAL(NULL != (void*)sos_zero_physpage);
   sos_physmem_ref_physpage_at(sos_zero_physpage);
 
   /* Allocate the VR/AS caches */
   cache_of_as
     = sos_kmem_cache_create("Address space structures",
                             sizeof(struct sos_umem_vmm_as),
                             1, 0,
                             SOS_KSLAB_CREATE_MAP
                             | SOS_KSLAB_CREATE_ZERO);
   if (! cache_of_as)
     {
       sos_physmem_unref_physpage(sos_zero_physpage);
       return -SOS_ENOMEM;
     }
 
   cache_of_vr
     = sos_kmem_cache_create("Virtual Region structures",
                             sizeof(struct sos_umem_vmm_vr),
                             1, 0,
                             SOS_KSLAB_CREATE_MAP
                             | SOS_KSLAB_CREATE_ZERO);
   if (! cache_of_vr)
     {
       sos_physmem_unref_physpage(sos_zero_physpage);
       sos_kmem_cache_destroy(cache_of_as);
       return -SOS_ENOMEM;
     }
 
   return SOS_OK;
 }
 
 
 struct sos_umem_vmm_as *
 sos_umem_vmm_create_empty_as(struct sos_process *owner)
 {
   struct sos_umem_vmm_as * as
     = (struct sos_umem_vmm_as *) sos_kmem_cache_alloc(cache_of_as, 0);
   if (! as)
     return NULL;
 
   as->mm_context = sos_mm_context_create();
   if (NULL == as->mm_context)
     {
       /* Error */
       sos_kmem_cache_free((sos_vaddr_t)as);
       return NULL;
     }
 
   as->process = owner;
   return as;
 }
 
 
 struct sos_umem_vmm_as *
 sos_umem_vmm_duplicate_current_thread_as(struct sos_process *owner)
 {
   __label__ undo_creation;
   struct sos_umem_vmm_as * my_as;
   struct sos_umem_vmm_vr * model_vr;
   int nb_vr;
 
   struct sos_umem_vmm_as * new_as
     = (struct sos_umem_vmm_as *) sos_kmem_cache_alloc(cache_of_as, 0);
   if (! new_as)
     return NULL;
 
   my_as = sos_process_get_address_space(sos_thread_get_current()->process);
   new_as->process = owner;
   list_init_named(new_as->list_vr, prev_in_as, next_in_as);
 
   /*
    * Switch to the current threads' mm_context, as duplicating it implies
    * being able to configure some of its mappings as read-only (for
    * COW)
    */
   SOS_ASSERT_FATAL(SOS_OK
                    == sos_thread_prepare_user_space_access(my_as,
                                                            (sos_vaddr_t)
                                                              NULL));
 
   /* Copy the virtual regions */
   list_foreach_named(my_as->list_vr, model_vr, nb_vr, prev_in_as, next_in_as)
     {
       struct sos_umem_vmm_vr * vr;
 
       /* Prepare COW on the read/write private mappings */
       if ( !(model_vr->flags & SOS_VR_MAP_SHARED)
            && (model_vr->access_rights & SOS_VM_MAP_PROT_WRITE) )
         {
           /* Mark the underlying physical pages (if any) as
              read-only */
           SOS_ASSERT_FATAL(SOS_OK
                            == sos_paging_prepare_COW(model_vr->start,
                                                      model_vr->size));
         }
 
       /* Allocate a new virtual region and copy the 'model' into it */
       vr = (struct sos_umem_vmm_vr *) sos_kmem_cache_alloc(cache_of_vr, 0);
       if (! vr)
         goto undo_creation;
       memcpy(vr, model_vr, sizeof(*vr));
       vr->address_space = new_as;
 
       /* Signal the "new" mapping to the underlying VR mapper */
       if (vr->ops && vr->ops->ref)
         vr->ops->ref(vr);
 
       /* Insert the new VR into the new AS */
       list_add_tail_named(new_as->list_vr, vr, prev_in_as, next_in_as);
 
       /* Insert the new VR into the list of mappings of the resource */
       list_add_tail_named(model_vr->mapped_resource->list_vr, vr,
                           prev_in_mapped_resource,
                           next_in_mapped_resource);
     }
 
   /* Now copy the current MMU configuration */
   new_as->mm_context = sos_mm_context_duplicate(my_as->mm_context);
   if (NULL == new_as->mm_context)
     goto undo_creation;
 
   /* Correct behavior */
   new_as->heap_start = my_as->heap_start;
   new_as->heap_size  = my_as->heap_size;
   new_as->phys_total = my_as->phys_total;
   memcpy(& new_as->vm_total, & my_as->vm_total, sizeof(struct vm_usage));
   memcpy(& new_as->vm_shrd, & my_as->vm_shrd, sizeof(struct vm_usage));
   SOS_ASSERT_FATAL(SOS_OK == sos_thread_end_user_space_access());
   return new_as;
 
   /* Handle erroneous behavior */
  undo_creation:
   SOS_ASSERT_FATAL(SOS_OK == sos_thread_end_user_space_access());
   sos_umem_vmm_delete_as(new_as);
   return NULL;
 }
 
 
 sos_ret_t
 sos_umem_vmm_delete_as(struct sos_umem_vmm_as * as)
 {
   while(! list_is_empty_named(as->list_vr, prev_in_as, next_in_as))
     {
       struct sos_umem_vmm_vr * vr;
       vr = list_get_head_named(as->list_vr, prev_in_as, next_in_as);
 
       /* Remove the vr from the lists */
       list_pop_head_named(as->list_vr, prev_in_as, next_in_as);
       list_delete_named(vr->mapped_resource->list_vr, vr,
                         prev_in_mapped_resource,
                         next_in_mapped_resource);
 
       /* Signal to the underlying VR mapper that the mapping is
          suppressed */
       if (vr->ops)
         {
           if (vr->ops->unmap)
             vr->ops->unmap(vr, vr->start, vr->size);
           if (vr->ops->unref)
             vr->ops->unref(vr);
         }
 
       sos_kmem_cache_free((sos_vaddr_t)vr);
     }
   
   /* Release MMU configuration */
   if (as->mm_context)
     sos_mm_context_unref(as->mm_context);
 
   /* Now unallocate main address space construct */
   sos_kmem_cache_free((sos_vaddr_t)as);
 
   return SOS_OK;
 }
 
 
 struct sos_process *
 sos_umem_vmm_get_process(struct sos_umem_vmm_as * as)
 {
   return as->process;
 }
 
 
 struct sos_mm_context *
 sos_umem_vmm_get_mm_context(struct sos_umem_vmm_as * as)
 {
   return as->mm_context;
 }
 
 
 struct sos_umem_vmm_vr *
 sos_umem_vmm_get_vr_at_address(struct sos_umem_vmm_as * as,
                                sos_uaddr_t uaddr)
 {
   struct sos_umem_vmm_vr * vr;
   vr = find_enclosing_or_next_vr(as, uaddr);
   if (! vr)
     return NULL;
 
   /* Ok uaddr <= vr->end, but do we have uaddr > vr->start ? */
   if (uaddr < vr->start)
     return NULL;
 
   return vr;
 }
 
 
 struct sos_umem_vmm_as *
 sos_umem_vmm_get_as_of_vr(struct sos_umem_vmm_vr * vr)
 {
   return vr->address_space;
 }
 
 
 struct sos_umem_vmm_vr_ops *
 sos_umem_vmm_get_ops_of_vr(struct sos_umem_vmm_vr * vr)
 {
   return vr->ops;
 }
 
 
 sos_ui32_t sos_umem_vmm_get_prot_of_vr(struct sos_umem_vmm_vr * vr)
 {
   return vr->access_rights;
 }
 
 
 sos_ui32_t sos_umem_vmm_get_flags_of_vr(struct sos_umem_vmm_vr * vr)
 {
   return vr->flags;
 }
 
 
 struct sos_umem_vmm_mapped_resource *
 sos_umem_vmm_get_mapped_resource_of_vr(struct sos_umem_vmm_vr * vr)
 {
   return vr->mapped_resource;
 }
 
 
 sos_uaddr_t sos_umem_vmm_get_start_of_vr(struct sos_umem_vmm_vr * vr)
 {
   return vr->start;
 }
 
 
 sos_size_t sos_umem_vmm_get_size_of_vr(struct sos_umem_vmm_vr * vr)
 {
   return vr->size;
 }
 
 
 sos_luoffset_t sos_umem_vmm_get_offset_in_resource(struct sos_umem_vmm_vr * vr)
 {
   return vr->offset_in_resource;
 }
 
 
 sos_ret_t
 sos_umem_vmm_set_ops_of_vr(struct sos_umem_vmm_vr * vr,
                            struct sos_umem_vmm_vr_ops * ops)
 {
   /* Don't allow to overwrite any preceding VR ops */
   SOS_ASSERT_FATAL(NULL == vr->ops);
 
   vr->ops = ops;
   return SOS_OK;
 }
 
 
 /**
  * When resize asks to map the resource elsewhere, make sure not to
  * overwrite the offset_in_resource field
  */
 #define INTERNAL_MAP_CALLED_FROM_MREMAP (1 << 8)
 
 sos_ret_t
 sos_umem_vmm_map(struct sos_umem_vmm_as * as,
                  sos_uaddr_t * /*in/out*/uaddr, sos_size_t size,
                  sos_ui32_t access_rights,
                  sos_ui32_t flags,
                  struct sos_umem_vmm_mapped_resource * resource,
                  sos_luoffset_t offset_in_resource)
 {
   __label__ return_mmap;
   sos_uaddr_t hint_uaddr;
   struct sos_umem_vmm_vr *prev_vr, *next_vr, *vr, *preallocated_vr;
   sos_bool_t merge_with_preceding, merge_with_next, used_preallocated_vr;
   sos_bool_t internal_map_called_from_mremap
     = (flags & INTERNAL_MAP_CALLED_FROM_MREMAP);
 
   sos_ret_t retval     = SOS_OK;
   used_preallocated_vr = FALSE;
   hint_uaddr           = *uaddr;
 
   /* Default mapping address is NULL */
   *uaddr = (sos_vaddr_t)NULL;
 
   if (! resource)
     return -SOS_EINVAL;
   if (! resource->mmap)
     return -SOS_EPERM;
 
   if (! SOS_IS_PAGE_ALIGNED(hint_uaddr))
     return -SOS_EINVAL;
 
   if (size <= 0)
     return -SOS_EINVAL;
   size = SOS_PAGE_ALIGN_SUP(size);
 
   if (flags & SOS_VR_MAP_SHARED)
     {
       /* Make sure the mapped resource allows the required protection flags */
       if ( ( (access_rights & SOS_VM_MAP_PROT_READ)
              && !(resource->allowed_access_rights & SOS_VM_MAP_PROT_READ) )
            || ( (access_rights & SOS_VM_MAP_PROT_WRITE)
                 && !(resource->allowed_access_rights & SOS_VM_MAP_PROT_WRITE) )
            || ( (access_rights & SOS_VM_MAP_PROT_EXEC)
                 && !(resource->allowed_access_rights & SOS_VM_MAP_PROT_EXEC)) )
         return -SOS_EPERM;
     }
 
   /* Sanity checks over the offset_in_resource parameter */
   if ( !internal_map_called_from_mremap
        && ( resource->flags & SOS_MAPPED_RESOURCE_ANONYMOUS ) )
     /* Initial offset ignored for anonymous mappings */
     {
       /* Nothing to check */
     }
 
   /* Make sure that the offset in resource won't overflow */
   else if (offset_in_resource + size <= offset_in_resource)
     return -SOS_EINVAL;
 
   /* Filter out unsupported flags */
   access_rights &= (SOS_VM_MAP_PROT_READ
                     | SOS_VM_MAP_PROT_WRITE
                     | SOS_VM_MAP_PROT_EXEC);
   flags &= (SOS_VR_MAP_SHARED
             | SOS_VR_MAP_FIXED);
 
   /* Pre-allocate a new VR. Because once we found a valid slot inside
      the VR list, we don't want the list to be altered by another
      process */
   preallocated_vr
     = (struct sos_umem_vmm_vr *)sos_kmem_cache_alloc(cache_of_vr, 0);
   if (! preallocated_vr)
     return -SOS_ENOMEM;
 
   /* Compute the user address of the new mapping */
   if (flags & SOS_VR_MAP_FIXED)
     {
       /*
        * The address is imposed
        */
 
       /* Make sure the hint_uaddr hint is valid */
       if (hint_uaddr < SOS_PAGING_BASE_USER_ADDRESS)
         { retval = -SOS_EINVAL; goto return_mmap; }
       if (hint_uaddr > SOS_PAGING_TOP_USER_ADDRESS - size)
         { retval = -SOS_EINVAL; goto return_mmap; }
 
       /* Unmap any overlapped VR */
       retval = sos_umem_vmm_unmap(as, hint_uaddr, size);
       if (SOS_OK != retval)
         { goto return_mmap; }
     }
   else
     {
       /*
        * A free range has to be determined
        */
 
       /* Find a suitable free VR */
       hint_uaddr = find_first_free_interval(as, hint_uaddr, size);
       if (! hint_uaddr)
         { retval = -SOS_ENOMEM; goto return_mmap; }
     }
 
   /* For anonymous resource mappings, set the initial
      offset_in_resource to the initial virtual start address in user
      space */
   if ( !internal_map_called_from_mremap
        && (resource->flags & SOS_MAPPED_RESOURCE_ANONYMOUS ) )
     offset_in_resource = hint_uaddr;
 
   /* Lookup next and previous VR, if any. This will allow us to merge
      the regions, when possible */
   next_vr = find_enclosing_or_next_vr(as, hint_uaddr);
   if (next_vr)
     {
       /* Find previous VR, if any */
       prev_vr = next_vr->prev_in_as;
       /* The list is curcular: it may happen that we looped over the
          tail of the list (ie the list is a singleton) */
       if (prev_vr->start > hint_uaddr)
         prev_vr = NULL; /* No preceding VR */
     }
   else
     {
       /* Otherwise we went beyond the last VR */
       prev_vr = list_get_tail_named(as->list_vr, prev_in_as, next_in_as);
     }
 
   /* Merge with preceding VR ? */
   merge_with_preceding
     = ( (NULL != prev_vr)
         && (prev_vr->mapped_resource == resource)
         && (prev_vr->offset_in_resource + prev_vr->size == offset_in_resource)
         && (prev_vr->start + prev_vr->size == hint_uaddr)
         && (prev_vr->flags == flags)
         && (prev_vr->access_rights == access_rights) );
 
   /* Merge with next VR ? */
   merge_with_next
     = ( (NULL != next_vr)
         && (next_vr->mapped_resource == resource)
         && (offset_in_resource + size == next_vr->offset_in_resource)
         && (hint_uaddr + size == next_vr->start)
         && (next_vr->flags == flags)
         && (next_vr->access_rights == access_rights) );
 
   if (merge_with_preceding && merge_with_next)
     {
       /* Widen the prev_vr VR to encompass both the new VR and the next_vr */
       vr = prev_vr;
       vr->size += size + next_vr->size;
       
       /* Remove the next_vr VR */
       list_delete_named(as->list_vr, next_vr, prev_in_as, next_in_as);
       list_delete_named(next_vr->mapped_resource->list_vr, next_vr,
                         prev_in_mapped_resource, next_in_mapped_resource);
 
       if (next_vr->ops && next_vr->ops->unref)
         next_vr->ops->unref(next_vr);
 
       sos_kmem_vmm_free((sos_vaddr_t) next_vr);
     }
   else if (merge_with_preceding)
     {
       /* Widen the prev_vr VR to encompass the new VR */
       vr = prev_vr;
       vr->size += size;
     }
   else if (merge_with_next)
     {
       /* Widen the next_vr VR to encompass the new VR */
       vr = next_vr;
       vr->start -= size;
       vr->size  += size;
     }
   else
     {
       /* Allocate a brand new VR and insert it into the list */
 
       vr = preallocated_vr;
       used_preallocated_vr = TRUE;
 
       vr->start              = hint_uaddr;
       vr->size               = size;
       vr->access_rights      = access_rights;
       vr->flags              = flags;
       vr->mapped_resource    = resource;
       vr->offset_in_resource = offset_in_resource;
 
       /* Insert VR in address space */
       vr->address_space      = as;
       if (prev_vr)
         list_insert_after_named(as->list_vr, prev_vr, vr,
                                 prev_in_as, next_in_as);
       else
         list_add_head_named(as->list_vr, vr, prev_in_as, next_in_as);
 
       list_add_tail_named(vr->mapped_resource->list_vr, vr,
                           prev_in_mapped_resource,
                           next_in_mapped_resource);
       
       /* Signal the resource we are mapping it */
       if (resource && resource->mmap)
         {
           retval = resource->mmap(vr);
           if (SOS_OK != retval)
             {
               retval = sos_umem_vmm_unmap(as, vr->start, vr->size);
               goto return_mmap;
             }
 
           /* The page_in method is MANDATORY for mapped resources */
           SOS_ASSERT_FATAL(vr->ops && vr->ops->page_in);
         }
 
       if (vr->ops && vr->ops->ref)
         vr->ops->ref(vr);
     }
 
   /* Ok, fine, we got it right ! Return the address to the caller */
   *uaddr = hint_uaddr;
   as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                      size, 0, vr->access_rights);
   retval = SOS_OK;
 
  return_mmap:
   if (! used_preallocated_vr)
     sos_kmem_vmm_free((sos_vaddr_t)preallocated_vr);
     
   return retval;
 }
 
 
 sos_ret_t
 sos_umem_vmm_unmap(struct sos_umem_vmm_as * as,
                    sos_uaddr_t uaddr, sos_size_t size)
 {
   struct sos_umem_vmm_vr *vr, *preallocated_vr;
   sos_bool_t need_to_setup_mmu;
   sos_bool_t used_preallocated_vr;
 
   if (! SOS_IS_PAGE_ALIGNED(uaddr))
     return -SOS_EINVAL;
   if (size <= 0)
     return -SOS_EINVAL;
   size = SOS_PAGE_ALIGN_SUP(size);
 
   /* Make sure the uaddr is valid */
   if (uaddr < SOS_PAGING_BASE_USER_ADDRESS)
     return -SOS_EINVAL;
   if (uaddr > SOS_PAGING_TOP_USER_ADDRESS - size)
     return -SOS_EINVAL;
 
   /* In some cases, the unmapping might imply a VR to be split into
      2. Actually, allocating a new VR can be a blocking operation, but
      actually we can block now, it won't do no harm. But we must be
      careful not to block later, while altering the VR lists: that's
      why we pre-allocate now. */
   used_preallocated_vr = FALSE;
   preallocated_vr
     = (struct sos_umem_vmm_vr *)sos_kmem_cache_alloc(cache_of_vr, 0);
   if (! preallocated_vr)
     return -SOS_ENOMEM;
 
   /* Find any VR intersecting with the given interval */
   vr = find_first_intersecting_vr(as, uaddr, size);
 
   /* Unmap (part of) the VR covered by [uaddr .. uaddr+size[ */
   while (NULL != vr)
     {
       /* Went past the end of the *circular* list => back at the
          beginning ? */
       if (vr->start + vr->size <= uaddr)
         /* Yes, stop now */
         break;
 
       /* Went beyond the region to unmap ? */
       if (uaddr + size <= vr->start)
         /* Yes, stop now */
         break;
 
       /* VR totally unmapped ? */
       if ((vr->start >= uaddr)
           && (vr->start + vr->size <= uaddr + size))
         {
           struct sos_umem_vmm_vr *next_vr;
 
           /* Yes: signal we remove it completely */
           if (vr->ops && vr->ops->unmap)
             vr->ops->unmap(vr, vr->start, vr->size);
 
           /* Remove it from the AS list now */
           next_vr = vr->next_in_as;
           if (next_vr == vr) /* singleton ? */
             next_vr = NULL;
           list_delete_named(as->list_vr, vr, prev_in_as, next_in_as);
 
           /* Remove from the list of VRs mapping the resource */
           list_delete_named(vr->mapped_resource->list_vr, vr,
                             prev_in_mapped_resource,
                             next_in_mapped_resource);
 
           if (vr->ops && vr->ops->unref)
             vr->ops->unref(vr);
           
           as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                              vr->size, vr->access_rights, 0);
           sos_kmem_vmm_free((sos_vaddr_t)vr);
       
           /* Prepare next iteration */
           vr = next_vr;
           continue;
         }
 
       /* unmapped region lies completely INSIDE the the VR */
       else if ( (vr->start < uaddr)
                 && (vr->start + vr->size > uaddr + size) )
         {
           /* VR has to be split into 2 */
 
           /* Use the preallocated VR and copy the VR into it */
           used_preallocated_vr = TRUE;
           memcpy(preallocated_vr, vr, sizeof(*vr));
 
           /* Adjust the start/size of both VRs */
           preallocated_vr->start = uaddr + size;
           preallocated_vr->size  = vr->start + vr->size - (uaddr + size);
           preallocated_vr->offset_in_resource += uaddr + size - vr->start;
           vr->size                             = uaddr - vr->start;
 
           /* Insert the new VR into the list */
           list_insert_after_named(as->list_vr, vr, preallocated_vr,
                                   prev_in_as, next_in_as);
           list_add_tail_named(vr->mapped_resource->list_vr, preallocated_vr,
                               prev_in_mapped_resource,
                               next_in_mapped_resource);
 
           /* Signal the changes to the underlying resource */
           if (vr->ops && vr->ops->unmap)
             vr->ops->unmap(vr, uaddr, size);
           if (preallocated_vr->ops && preallocated_vr->ops->ref)
             preallocated_vr->ops->ref(preallocated_vr);
 
           /* Account for change in VRs */
           as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                              size, vr->access_rights, 0);
 
           /* No need to go further */
           break;
         }
 
       /* Unmapped region only affects the START address of the VR */
       else if (uaddr <= vr->start)
         {
           sos_size_t translation = uaddr + size - vr->start;
 
           /* Shift the VR */
           vr->size               -= translation;
           vr->offset_in_resource += translation;
           vr->start              += translation;
           
           /* Signal unmapping */
           if (vr->ops && vr->ops->unmap)
             vr->ops->unmap(vr, uaddr + size,
                            translation);
           
           /* Account for change in VRs */
           as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                              translation,
                                              vr->access_rights, 0);
 
           /* No need to go further, we reached the last VR that
              overlaps the unmapped region */
           break;
         }
 
       /* Unmapped region only affects the ENDING address of the VR */
       else if (uaddr + size >= vr->start + vr->size)
         {
           sos_size_t unmapped_size = vr->start + vr->size - uaddr;
 
           /* Resize VR */
           vr->size = uaddr - vr->start;
           
           /* Signal unmapping */
           if (vr->ops && vr->ops->unmap)
             vr->ops->unmap(vr, uaddr, unmapped_size);
 
           /* Account for change in VRs */
           as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                              unmapped_size,
                                              vr->access_rights, 0);
           
           vr = vr->next_in_as;
           continue;
         }
 
       sos_display_fatal_error("BUG uaddr=%x sz=%x vr_start=%x, vr_sz=%x",
                               uaddr, size, vr->start, vr->size);
     }
 
   need_to_setup_mmu = (sos_thread_get_current()->squatted_mm_context
                        != as->mm_context);
   if (need_to_setup_mmu)
     SOS_ASSERT_FATAL(SOS_OK
                      == sos_thread_prepare_user_space_access(as,
                                                              (sos_vaddr_t)
                                                                NULL));
   {
     sos_ret_t sz_unmapped = sos_paging_unmap_interval(uaddr, size);
     SOS_ASSERT_FATAL(sz_unmapped >= 0);
     as->phys_total -= sz_unmapped;
   }
   if (need_to_setup_mmu)
     SOS_ASSERT_FATAL(SOS_OK == sos_thread_end_user_space_access());
 
   if (! used_preallocated_vr)
     sos_kmem_vmm_free((sos_vaddr_t)preallocated_vr);
 
   return SOS_OK;
 }
 
 
 sos_ret_t
 sos_umem_vmm_chprot(struct sos_umem_vmm_as * as,
                     sos_uaddr_t uaddr, sos_size_t size,
                     sos_ui32_t new_access_rights)
 {
   struct sos_umem_vmm_vr *start_vr, *vr,
     *preallocated_middle_vr, *preallocated_right_vr;
   sos_bool_t used_preallocated_middle_vr, used_preallocated_right_vr;
 
   if (! SOS_IS_PAGE_ALIGNED(uaddr))
     return -SOS_EINVAL;
   if (size <= 0)
     return -SOS_EINVAL;
   size = SOS_PAGE_ALIGN_SUP(size);
 
   /* Make sure the uaddr is valid */
   if (uaddr < SOS_PAGING_BASE_USER_ADDRESS)
     return -SOS_EINVAL;
   if (uaddr > SOS_PAGING_TOP_USER_ADDRESS - size)
     return -SOS_EINVAL;
 
   /* Pre-allocate 2 new VRs (same reason as for unmap). Because chprot
      may imply at most 2 regions to be split */
   used_preallocated_middle_vr = FALSE;
   used_preallocated_right_vr  = FALSE;
   preallocated_middle_vr
     = (struct sos_umem_vmm_vr *)sos_kmem_cache_alloc(cache_of_vr, 0);
   if (! preallocated_middle_vr)
     return -SOS_ENOMEM;
   preallocated_right_vr
     = (struct sos_umem_vmm_vr *)sos_kmem_cache_alloc(cache_of_vr, 0);
   if (! preallocated_right_vr)
     {
       sos_kmem_vmm_free((sos_vaddr_t)preallocated_middle_vr);
       return -SOS_ENOMEM;
     }
 
   /* Find any VR intersecting with the given interval */
   start_vr = find_first_intersecting_vr(as, uaddr, size);
   if (NULL == start_vr)
     return SOS_OK;
 
   /* First of all: make sure we are allowed to change the access
      rights of all the VRs concerned by the chprot */
   vr = start_vr;
   while (TRUE)
     {
       /* Went past the end of the *circular* list => back at the
          begining ? */
       if (vr->start + vr->size <= uaddr)
         /* Yes, stop now */
         break;
 
       /* Went beyond the region to chprot ? */
       if (uaddr + size < vr->start)
         /* Yes, stop now */
         break;
 
       if (vr->flags & SOS_VR_MAP_SHARED)
         {
           /* Make sure the mapped resource allows the required
              protection flags */
           if ( ( (new_access_rights & SOS_VM_MAP_PROT_READ)
                  && !(vr->mapped_resource->allowed_access_rights
                       & SOS_VM_MAP_PROT_READ) )
                || ( (new_access_rights & SOS_VM_MAP_PROT_WRITE)
                     && !(vr->mapped_resource->allowed_access_rights
                          & SOS_VM_MAP_PROT_WRITE) )
                || ( (new_access_rights & SOS_VM_MAP_PROT_EXEC)
                     && !(vr->mapped_resource->allowed_access_rights
                          & SOS_VM_MAP_PROT_EXEC) ) )
             return -SOS_EPERM;
         }
 
       vr = vr->next_in_as;
     }
 
   /* Change the access rights of the VRs covered by [uaddr
      .. uaddr+size[ */
   vr = start_vr;
   while (TRUE)
     {
 
       /* Went past the end of the *circular* list => back at the
          begining ? */
       if (vr->start + vr->size <= uaddr)
         /* Yes, stop now */
         break;
 
       /* Went beyond the region to chprot ? */
       if (uaddr + size <= vr->start)
         /* Yes, stop now */
         break;
 
       /* Access rights unchanged ? */
       if (vr->access_rights == new_access_rights)
         /* nop */
         {
           vr = vr->next_in_as;
           continue;
         }
 
       /* VR totally chprot ? */
       if ((vr->start >= uaddr)
           && (vr->start + vr->size <= uaddr + size))
         {
           /* Account for change in VRs */
           as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                              vr->size, vr->access_rights,
                                              new_access_rights);
           vr->access_rights = new_access_rights;
 
           if (vr->flags & SOS_VR_MAP_SHARED)
             /* For shared mappings: effectively change the access
                rights of the physical pages  */
             sos_paging_set_prot_of_interval(vr->start, vr->size,
                                             new_access_rights);
           else
             /* Private mapping */
             {
               /* For private mappings, we set the new access_rights
                  only if it becomes read-only. For private mappings
                  that become writable, we don't do anything: we keep
                  the access rights unchanged to preserve the COW
                  semantics */
               if (! (new_access_rights & SOS_VM_MAP_PROT_WRITE))
                 sos_paging_set_prot_of_interval(vr->start, vr->size,
                                                 new_access_rights);
             }
 
           vr = vr->next_in_as;
           continue;
         }
 
       /* chprot region lies completely INSIDE the VR */
       else if ( (vr->start < uaddr)
                 && (vr->start + vr->size > uaddr + size) )
         {
           /* VR has to be split into 3 */
 
           /* Use the preallocated VRs and copy the VR into them */
           SOS_ASSERT_FATAL(! used_preallocated_middle_vr);
           SOS_ASSERT_FATAL(! used_preallocated_right_vr);
           used_preallocated_middle_vr = TRUE;
           memcpy(preallocated_middle_vr, vr, sizeof(*vr));
           used_preallocated_right_vr = TRUE;
           memcpy(preallocated_right_vr, vr, sizeof(*vr));
 
           /* Adjust the start/size of the VRs */
           preallocated_middle_vr->start = uaddr;
           preallocated_middle_vr->size  = size;
           preallocated_right_vr->start  = uaddr + size;
           preallocated_right_vr->size   = vr->start + vr->size
                                             - (uaddr + size);
           preallocated_middle_vr->offset_in_resource
             += uaddr - vr->start;
           preallocated_right_vr->offset_in_resource
             += uaddr + size - vr->start;
           vr->size = uaddr - vr->start;
 
           /* Account for change in VRs */
           preallocated_middle_vr->access_rights = new_access_rights;
           as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                              size, vr->access_rights,
                                              new_access_rights);
 
           /* Insert the new VRs into the lists */
           list_insert_after_named(as->list_vr, vr, preallocated_middle_vr,
                                   prev_in_as, next_in_as);
           list_insert_after_named(as->list_vr, preallocated_middle_vr,
                                   preallocated_right_vr,
                                   prev_in_as, next_in_as);
 
           list_add_tail_named(vr->mapped_resource->list_vr,
                               preallocated_middle_vr,
                               prev_in_mapped_resource,
                               next_in_mapped_resource);
           list_add_tail_named(vr->mapped_resource->list_vr,
                               preallocated_right_vr,
                               prev_in_mapped_resource,
                               next_in_mapped_resource);
 
           /* Effectively change the access rights of the physical pages */
           if (!(preallocated_middle_vr->flags & SOS_VR_MAP_SHARED)
               && (new_access_rights & SOS_VM_MAP_PROT_WRITE))
             /* For private mappings with write access, prepare for COW */
             sos_paging_prepare_COW(preallocated_middle_vr->start,
                                    preallocated_middle_vr->size);
           else
             sos_paging_set_prot_of_interval(preallocated_middle_vr->start,
                                             preallocated_middle_vr->size,
                                             new_access_rights);
 
           if (preallocated_right_vr->ops && preallocated_right_vr->ops->ref)
             preallocated_right_vr->ops->ref(preallocated_right_vr);
           if (preallocated_middle_vr->ops && preallocated_middle_vr->ops->ref)
             preallocated_middle_vr->ops->ref(preallocated_middle_vr);
 
           /* No need to go further */
           break;
         }
 
       /* Chprot region only affects the START address of the VR */
       else if (uaddr <= vr->start)
         {
           /* Split the region into 2 */
           sos_uoffset_t offset_in_region = uaddr + size - vr->start;
 
           /* Use the preallocated VRs and copy the VR into them */
           SOS_ASSERT_FATAL(! used_preallocated_middle_vr);
           used_preallocated_middle_vr = TRUE;
           memcpy(preallocated_middle_vr, vr, sizeof(*vr));
 
           /* Adjust the start/size of the VRs */
           preallocated_middle_vr->start += offset_in_region;
           preallocated_middle_vr->size  -= offset_in_region;
           vr->size                       = offset_in_region;
           preallocated_middle_vr->offset_in_resource += offset_in_region;
 
           /* Account for change in VRs */
           as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                              vr->size,
                                              vr->access_rights,
                                              new_access_rights);
           vr->access_rights = new_access_rights;
 
           /* Insert the new VR into the lists */
           list_insert_after_named(as->list_vr, vr,
                                   preallocated_middle_vr,
                                   prev_in_as, next_in_as);
           list_add_tail_named(vr->mapped_resource->list_vr,
                               preallocated_middle_vr,
                               prev_in_mapped_resource,
                               next_in_mapped_resource);
 
           /* Effectively change the access rights of the physical pages */
           if (!(vr->flags & SOS_VR_MAP_SHARED)
               && (new_access_rights & SOS_VM_MAP_PROT_WRITE))
             /* For private mappings with write access, prepare for COW */
             sos_paging_prepare_COW(vr->start, vr->size);
           else
             sos_paging_set_prot_of_interval(vr->start, vr->size,
                                             new_access_rights);
 
           if (preallocated_middle_vr->ops && preallocated_middle_vr->ops->ref)
             preallocated_middle_vr->ops->ref(preallocated_middle_vr);
 
           /* Ne need to go further (we reached the last VR that
              overlaps the given interval to chprot) */
           break;
         }
 
       /* Chprot region only affects the ENDING address of the VR */
       else if (uaddr + size >= vr->start + vr->size)
         {
           /* Split the region into 2 */
           sos_uoffset_t offset_in_region = uaddr - vr->start;
 
           /* Use the preallocated VRs and copy the VR into them */
           SOS_ASSERT_FATAL(! used_preallocated_right_vr);
           used_preallocated_right_vr = TRUE;
           memcpy(preallocated_right_vr, vr, sizeof(*vr));
 
           /* Adjust the start/size of the VRs */
           preallocated_right_vr->start        += offset_in_region;
           preallocated_right_vr->size         -= offset_in_region;
           vr->size                             = offset_in_region;
           preallocated_right_vr->offset_in_resource += offset_in_region;
 
           /* Account for change in VRs */
           as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                              preallocated_right_vr->size,
                                              vr->access_rights,
                                              new_access_rights);
           preallocated_right_vr->access_rights = new_access_rights;
 
           /* Insert the new VR into the lists */
           list_insert_after_named(as->list_vr, vr,
                                   preallocated_right_vr,
                                   prev_in_as, next_in_as);
           list_add_tail_named(vr->mapped_resource->list_vr,
                               preallocated_right_vr,
                               prev_in_mapped_resource,
                               next_in_mapped_resource);
 
           /* Effectively change the access rights of the physical pages */
           if (!(preallocated_right_vr->flags & SOS_VR_MAP_SHARED)
               && (new_access_rights & SOS_VM_MAP_PROT_WRITE))
             /* For private mappings with write access, prepare for COW */
             sos_paging_prepare_COW(preallocated_right_vr->start,
                                    preallocated_right_vr->size);
           else
             sos_paging_set_prot_of_interval(preallocated_right_vr->start,
                                             preallocated_right_vr->size,
                                             new_access_rights);
 
           if (preallocated_right_vr->ops && preallocated_right_vr->ops->ref)
             preallocated_right_vr->ops->ref(preallocated_right_vr);
 
           vr = vr->next_in_as;
           continue;
         }
 
       sos_display_fatal_error("BUG");
     }
 
   if (! used_preallocated_middle_vr)
     sos_kmem_vmm_free((sos_vaddr_t)preallocated_middle_vr);
   if (! used_preallocated_right_vr)
     sos_kmem_vmm_free((sos_vaddr_t)preallocated_right_vr);
 
   return SOS_OK;
 }
 
 
 sos_ret_t
 sos_umem_vmm_sync(struct sos_umem_vmm_as * as,
                   sos_uaddr_t uaddr, sos_size_t size,
                   sos_ui32_t flags)
 {
   if (! SOS_IS_PAGE_ALIGNED(uaddr))
     return -SOS_EINVAL;
   if (size <= 0)
     return -SOS_EINVAL;
   size = SOS_PAGE_ALIGN_SUP(size);
 
   /* Make sure the uaddr is valid */
   if (uaddr < SOS_PAGING_BASE_USER_ADDRESS)
     return -SOS_EINVAL;
   if (uaddr > SOS_PAGING_TOP_USER_ADDRESS - size)
     return -SOS_EINVAL;
 
   /* Go from page to page, and for each dirty page in the region, call
      the sync_page method */
   while (TRUE)
     {
       struct sos_umem_vmm_vr *vr;
 
       if (size <= 0)
         break;
 
       /* Find any VR intersecting with the given interval */
       vr = find_first_intersecting_vr(as, uaddr, size);
       if (NULL == vr)
         break;
 
       /* For private or anonymous mappings => no backing store */
       if ( !(vr->flags & SOS_VR_MAP_SHARED)
            || (vr->mapped_resource->flags & SOS_MAPPED_RESOURCE_ANONYMOUS)
 
            /* Likewise for non msync-able regions */
            || ! vr->ops->sync_page )
         {
           if (size <= vr->size)
             break;
 
           uaddr += vr->size;
           size  -= vr->size;
         }
 
       /* Find the next dirty page in this VR */
       for ( ; (size > 0)
               && (uaddr - vr->start < vr->size) ;
             uaddr += SOS_PAGE_SIZE,
               size -= SOS_PAGE_SIZE)
         if (sos_paging_is_dirty(uaddr))
           {
             /* Synchronize it with its backing store */
             vr->ops->sync_page(vr, uaddr, flags);
             uaddr += SOS_PAGE_SIZE;
             size  -= SOS_PAGE_SIZE;
             break;
           }
     }
 
   return SOS_OK;
 }
 
 
 sos_ret_t
 sos_umem_vmm_resize(struct sos_umem_vmm_as * as,
                     sos_uaddr_t old_uaddr, sos_size_t old_size,
                     sos_uaddr_t *new_uaddr, sos_size_t new_size,
                     sos_ui32_t flags)
 {
   sos_luoffset_t new_offset_in_resource;
   sos_bool_t must_move_vr = FALSE;
   struct sos_umem_vmm_vr *vr, *prev_vr, *next_vr;
 
   /* Make sure the new uaddr is valid */
   if (*new_uaddr < SOS_PAGING_BASE_USER_ADDRESS)
     return -SOS_EINVAL;
   if (*new_uaddr > SOS_PAGING_TOP_USER_ADDRESS - new_size)
     return -SOS_EINVAL;
 
   old_uaddr = SOS_PAGE_ALIGN_INF(old_uaddr);
   old_size  = SOS_PAGE_ALIGN_SUP(old_size);
   if (! SOS_IS_PAGE_ALIGNED(*new_uaddr))
     return -SOS_EINVAL;
   if (new_size <= 0)
     return -SOS_EINVAL;
   new_size = SOS_PAGE_ALIGN_SUP(new_size);
   
   /* Lookup a VR overlapping the address range */
   vr = find_first_intersecting_vr(as, old_uaddr, old_size);
   if (! vr)
     return -SOS_EINVAL;
   
   /* Make sure there is exactly ONE VR overlapping the area */
   if ( (vr->start > old_uaddr)
        || (vr->start + vr->size < old_uaddr + old_size) )
     return -SOS_EINVAL;
 
   /* Retrieve the prev/next VR if they exist (the VR are on circular
      list) */
   prev_vr = vr->prev_in_as;
   if (prev_vr->start >= vr->start)
     prev_vr = NULL;
   next_vr = vr->prev_in_as;
   if (next_vr->start <= vr->start)
     next_vr = NULL;
 
   /*
    * Compute new offset inside the mapped resource, if any
    */
 
   /* Don't allow to resize if the uaddr goes beyond the 'offset 0' of
      the resource */
   if ( (*new_uaddr < vr->start)
        && (vr->start - *new_uaddr > vr->offset_in_resource) )
     return -SOS_EINVAL;
   
   /* Compute new offset in the resource (overflow-safe) */
   if (vr->start > *new_uaddr)
     new_offset_in_resource
       = vr->offset_in_resource
       - (vr->start - *new_uaddr);
   else
     new_offset_in_resource
       = vr->offset_in_resource
       + (*new_uaddr - vr->start);
 
   /* If other VRs would be affected by this resizing, then the VR must
      be moved */
   if (prev_vr && (prev_vr->start + prev_vr->size > *new_uaddr))
     must_move_vr |= TRUE;
   if (next_vr && (next_vr->start < *new_uaddr + new_size))
     must_move_vr |= TRUE;
 
   /* If VR would be out-of-user-space, it must be moved */
   if (*new_uaddr < SOS_PAGING_BASE_USER_ADDRESS)
     must_move_vr |= TRUE;
   if (*new_uaddr > SOS_PAGING_TOP_USER_ADDRESS - new_size)
     must_move_vr |= TRUE;
 
   /* The VR must be moved but the user forbids it */
   if ( must_move_vr && !(flags & SOS_VR_REMAP_MAYMOVE) )
     return -SOS_EINVAL;
 
   /* If the VR must be moved, we simply map the resource elsewhere and
      unmap the current VR */
   if (must_move_vr)
     {
       sos_uaddr_t uaddr, result_uaddr;
       sos_ret_t retval;
 
       result_uaddr = *new_uaddr;
       retval = sos_umem_vmm_map(as, & result_uaddr, new_size,
                                 vr->access_rights,
                                 vr->flags | INTERNAL_MAP_CALLED_FROM_MREMAP,
                                 vr->mapped_resource,
                                 new_offset_in_resource);
       if (SOS_OK != retval)
         return retval;
 
       /* Remap the physical pages at their new address */
       for (uaddr = vr->start ;
            uaddr < vr->start + vr->size ;
            uaddr += SOS_PAGE_SIZE)
         {
           sos_paddr_t paddr;
           sos_ui32_t  prot;
           sos_uaddr_t vaddr;
           
           if (uaddr < *new_uaddr)
             continue;
           if (uaddr > *new_uaddr + new_size)
             continue;
 
           /* Compute destination virtual address (should be
              overflow-safe) */
           if (vr->start >= *new_uaddr)
             vaddr = result_uaddr
               + (uaddr - vr->start)
               + (vr->start - *new_uaddr);
           else
             vaddr = result_uaddr
               + (uaddr - vr->start)
               - (*new_uaddr - vr->start);
 
           paddr = sos_paging_get_paddr(uaddr);
           if (! paddr)
             /* No physical page mapped at this address yet */
             continue;
 
           prot  = sos_paging_get_prot(uaddr);
           SOS_ASSERT_FATAL(prot);
 
           /* Remap it at its destination address */
           retval = sos_paging_map(paddr, vaddr, TRUE, prot);
           if (SOS_OK != retval)
             {
               sos_umem_vmm_unmap(as, result_uaddr, new_size);
               return retval;
             }
         }
 
       retval = sos_umem_vmm_unmap(as, vr->start, vr->size);
       if (SOS_OK != retval)
         {
           sos_umem_vmm_unmap(as, result_uaddr, new_size);
           return retval;
         }
 
       *new_uaddr = result_uaddr;
       return retval;
     }
 
   /* Otherwise we simply resize the VR, taking care of unmapping
      what's been unmapped  */
 
   if (*new_uaddr + new_size < vr->start + vr->size)
     sos_umem_vmm_unmap(as, *new_uaddr + new_size,
                        vr->start + vr->size - (*new_uaddr + new_size));
   else
     {
       as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                          *new_uaddr + new_size
                                            - (vr->start + vr->size),
                                          0, vr->access_rights);
       vr->size += *new_uaddr + new_size - (vr->start + vr->size);
     }
   
   if (*new_uaddr > vr->start)
     sos_umem_vmm_unmap(as, vr->start, *new_uaddr - vr->start);
   else
     {
       as_account_change_of_vr_protection(as, vr->flags & SOS_VR_MAP_SHARED,
                                          vr->start - *new_uaddr,
                                          0, vr->access_rights);
       vr->size  += vr->start - *new_uaddr;
       vr->start  = *new_uaddr;
       vr->offset_in_resource = new_offset_in_resource; 
     }
 
   SOS_ASSERT_FATAL(vr->start == *new_uaddr);
   SOS_ASSERT_FATAL(vr->size  == new_size);
   SOS_ASSERT_FATAL(vr->offset_in_resource == new_offset_in_resource);
 
   return SOS_OK;
 }
 
 
 sos_ret_t sos_umem_vmm_try_resolve_page_fault(sos_uaddr_t uaddr,
                                               sos_bool_t write_access,
                                               sos_bool_t user_access)
 {
   struct sos_process     *process = sos_thread_get_current()->process;
   struct sos_umem_vmm_as *as;
   struct sos_umem_vmm_vr *vr;
 
   if (! process)
     return -SOS_EFAULT;
 
   as = sos_process_get_address_space(process);
   if (! as)
     return -SOS_EFAULT;
 
   vr = find_first_intersecting_vr(as, uaddr, 1);
   if (! vr)
     return -SOS_EFAULT;
 
   /* Write on a read-only VR */
   if (write_access && !(vr->access_rights & SOS_VM_MAP_PROT_WRITE))
     return -SOS_EFAULT;
 
   /* Write on a COW VR */
   if (write_access && !(vr->flags & SOS_VR_MAP_SHARED))
     {
       if (SOS_OK == sos_paging_try_resolve_COW(uaddr))
         {
           as->pgflt_cow ++;
           return SOS_OK;
         }
     }
 
   /* Ask the underlying resource to resolve the page fault */
   if (SOS_OK != vr->ops->page_in(vr, uaddr, write_access))
     {
       as->pgflt_invalid ++;
       return -SOS_EFAULT;
     }
 
   as->phys_total += SOS_PAGE_SIZE;
   as->pgflt_page_in ++;
 
   /* For a private mapping, keep the mapping read-only */
   if (!(vr->flags & SOS_VR_MAP_SHARED))
     {
       sos_paging_prepare_COW(SOS_PAGE_ALIGN_INF(uaddr),
                              SOS_PAGE_SIZE);
     }
 
   return SOS_OK;
 }
 
 
 sos_ret_t
 sos_umem_vmm_init_heap(struct sos_umem_vmm_as * as,
                        sos_uaddr_t heap_start)
 {
   SOS_ASSERT_FATAL(! as->heap_start);
 
   as->heap_start = heap_start;
   as->heap_size  = 0;
   return SOS_OK;
 }
 
 
 sos_uaddr_t
 sos_umem_vmm_brk(struct sos_umem_vmm_as * as,
                  sos_uaddr_t new_top_uaddr)
 {
   sos_uaddr_t new_start;
   sos_size_t  new_size;
   SOS_ASSERT_FATAL(as->heap_start);
 
   if (! new_top_uaddr)
     return as->heap_start + as->heap_size;
 
   if (new_top_uaddr == as->heap_start + as->heap_size)
     return as->heap_start + as->heap_size;
  
   if (new_top_uaddr < as->heap_start)
     return (sos_uaddr_t)NULL;
 
   new_top_uaddr = SOS_PAGE_ALIGN_SUP(new_top_uaddr);
   new_start = as->heap_start;
   new_size  = new_top_uaddr - as->heap_start;
 
   /* First call to brk: we must map /dev/zero */
   if (! as->heap_size)
     {
       if (SOS_OK != sos_dev_zero_map(as, & as->heap_start,
                                      new_size,
                                      SOS_VM_MAP_PROT_READ
                                      | SOS_VM_MAP_PROT_WRITE,
                                      0 /* private non-fixed */))
         return (sos_uaddr_t)NULL;
 
       as->heap_size = new_size;
       return as->heap_start + as->heap_size;
     }
 
   /* Otherwise we just have to unmap or resize the region */
   if (new_size <= 0)
     {
       if (SOS_OK != sos_umem_vmm_unmap(as,
                                        as->heap_start, as->heap_size))
         return (sos_uaddr_t)NULL;
     }
   else
     {
       if (SOS_OK != sos_umem_vmm_resize(as,
                                         as->heap_start, as->heap_size,
                                         & new_start, new_size,
                                         0))
         return (sos_uaddr_t)NULL;
     }
 
   SOS_ASSERT_FATAL(new_start == as->heap_start);
   as->heap_size = new_size;
   return new_top_uaddr;
 }
 
 
 static struct sos_umem_vmm_vr *
 find_enclosing_or_next_vr(struct sos_umem_vmm_as * as,
                           sos_uaddr_t uaddr)
 {
   struct sos_umem_vmm_vr *vr;
   int nb_vr;
 
   if (uaddr < SOS_PAGING_BASE_USER_ADDRESS)
     return NULL;
   if (uaddr > SOS_PAGING_TOP_USER_ADDRESS)
     return NULL;
 
   list_foreach_named(as->list_vr, vr, nb_vr, prev_in_as, next_in_as)
     {
       /* Equivalent to "if (uaddr < vr->start + vr->size)" but more
          robust (resilient to integer overflows) */
       if (uaddr <= vr->start + (vr->size - 1))
         return vr;
     }
 
   return NULL;
 }
 
 
 static struct sos_umem_vmm_vr *
 find_first_intersecting_vr(struct sos_umem_vmm_as * as,
                            sos_uaddr_t start_uaddr, sos_size_t size)
 {
   struct sos_umem_vmm_vr * vr;
   vr = find_enclosing_or_next_vr(as, start_uaddr);
   if (! vr)
     return NULL;
 
   if (start_uaddr + size <= vr->start)
     return NULL;
 
   return vr;
 }
 
 
 static sos_uaddr_t
 find_first_free_interval(struct sos_umem_vmm_as * as,
                          sos_uaddr_t hint_uaddr, sos_size_t size)
 {
   struct sos_umem_vmm_vr * initial_vr, * vr;
 
   if (hint_uaddr < SOS_PAGING_BASE_USER_ADDRESS)
     hint_uaddr = SOS_PAGING_BASE_USER_ADDRESS;
 
   if (hint_uaddr > SOS_PAGING_TOP_USER_ADDRESS - size + 1)
     return (sos_uaddr_t)NULL;
 
   initial_vr = vr = find_enclosing_or_next_vr(as, hint_uaddr);
   if (! vr)
     /* Great, there is nothing after ! */
     return hint_uaddr;
 
   /* Scan the remaining VRs in the list */
   do
     {
       /* Is there enough space /before/ that VR ? */
       if (hint_uaddr + size <= vr->start)
         /* Great ! */
         return hint_uaddr;
 
       /* Is there any VR /after/ this one, or do we have to wrap back
          at the begining of the user space ? */
       if (vr->next_in_as->start >= hint_uaddr)
         /* Ok, the next VR is really after us */
         hint_uaddr = vr->start + vr->size;
       else
         {
           /* No: wrapping up */
 
           /* Is there any space before the end of user space ? */
           if (hint_uaddr <= SOS_PAGING_TOP_USER_ADDRESS - size)
             return hint_uaddr;
 
           hint_uaddr = SOS_PAGING_BASE_USER_ADDRESS;
         }
 
       /* Prepare to look after this VR */
       vr = vr->next_in_as;
     }
   while (vr != initial_vr);
 
   /* Reached the end of the list and did not find anything ?... Look
      at the space after the last VR */
 
   return (sos_uaddr_t)NULL;
 }
 
 
 static void
 as_account_change_of_vr_protection(struct sos_umem_vmm_as * as,
                                    sos_bool_t is_shared,
                                    sos_size_t size,
                                    sos_ui32_t prev_access_rights,
                                    sos_ui32_t new_access_rights)
 {
   if (prev_access_rights == new_access_rights)
     return;
 
 #define _UPDATE_VMSTAT(field,is_increment) \
   ({ if (is_increment > 0) \
        as->field += size; \
      else \
        { SOS_ASSERT_FATAL(as->field >= size); as->field -= size; } })
 #define UPDATE_VMSTAT(field,is_increment) \
   ({ if (is_shared) _UPDATE_VMSTAT(vm_shrd.field, is_increment); \
      _UPDATE_VMSTAT(vm_total.field, is_increment); \
      SOS_ASSERT_FATAL(as->vm_total.field >= as->vm_shrd.field); })
 
   if ( (new_access_rights & SOS_VM_MAP_PROT_WRITE)
        && !(prev_access_rights & SOS_VM_MAP_PROT_WRITE))
     {
       UPDATE_VMSTAT(rw, +1);
       if (prev_access_rights & SOS_VM_MAP_PROT_READ)
         UPDATE_VMSTAT(ro, -1);
     }
   else if ( !(new_access_rights & SOS_VM_MAP_PROT_WRITE)
             && (prev_access_rights & SOS_VM_MAP_PROT_WRITE))
     {
       if (new_access_rights & SOS_VM_MAP_PROT_READ)
         UPDATE_VMSTAT(ro, +1);
       UPDATE_VMSTAT(rw, -1);
     }
   else if (new_access_rights & SOS_VM_MAP_PROT_READ)
     UPDATE_VMSTAT(ro, +1);
   else if (!(new_access_rights & SOS_VM_MAP_PROT_READ))
     UPDATE_VMSTAT(ro, -1);
 
   if ( (new_access_rights & SOS_VM_MAP_PROT_EXEC)
        && !(prev_access_rights & SOS_VM_MAP_PROT_EXEC))
     {
       UPDATE_VMSTAT(code, +1);
     }
   else if ( !(new_access_rights & SOS_VM_MAP_PROT_EXEC)
             && (prev_access_rights & SOS_VM_MAP_PROT_EXEC))
     {
       UPDATE_VMSTAT(code, -1);
     }
 
   if (new_access_rights && !prev_access_rights)
     UPDATE_VMSTAT(overall, +1);
   else if (!new_access_rights && prev_access_rights)
     UPDATE_VMSTAT(overall, -1);
 
 }