# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1679766342 -3600
# Node ID 1ce97d0e88232de7b2373730322da89cdea3d243
# Parent  754959243588dbc143ca0140ee2e0fd7bf149395
Added initial support for detaching regions. Without this, it is likely that
file access operations will eventually fail due to unanticipated side-effects
resulting from the accumulation of regions and dataspaces in the region mapper.

diff -r 754959243588 -r 1ce97d0e8823 libexec/include/exec/internal_pager.h
--- a/libexec/include/exec/internal_pager.h	Fri Mar 24 16:14:44 2023 +0100
+++ b/libexec/include/exec/internal_pager.h	Sat Mar 25 18:45:42 2023 +0100
@@ -59,6 +59,9 @@
   virtual long attach(address_t *start, address_t size, map_flags_t flags,
                       l4_cap_idx_t ds, address_t offset, unsigned char align);
 
+  virtual long detach(address_t addr, address_t size, map_flags_t flags,
+                      address_t *start, address_t *rsize, l4_cap_idx_t *ds);
+
   virtual long reserve_area(address_t *start, address_t size, map_flags_t flags,
                             unsigned char align);
 };
diff -r 754959243588 -r 1ce97d0e8823 libexec/include/exec/memory_area.h
--- a/libexec/include/exec/memory_area.h	Fri Mar 24 16:14:44 2023 +0100
+++ b/libexec/include/exec/memory_area.h	Sat Mar 25 18:45:42 2023 +0100
@@ -95,7 +95,7 @@
 
   /* Support for finding regions. */
 
-  virtual long find(address_t addr, MemoryArea **area);
+  virtual long find(address_t addr, MemoryArea **area, MemoryArea **parent);
 
   /* Support for finding areas. */
 
@@ -124,7 +124,7 @@
 
   /* Support for finding areas. */
 
-  virtual long find(address_t addr, MemoryArea **area);
+  virtual long find(address_t addr, MemoryArea **area, MemoryArea **parent);
 };
 
 
@@ -162,7 +162,7 @@
 
   /* Support for finding areas. */
 
-  virtual long find(address_t addr, MemoryArea **area);
+  virtual long find(address_t addr, MemoryArea **area, MemoryArea **parent);
 
   virtual long find(address_t *start, address_t *size, map_flags_t flags,
                     unsigned char align, MemoryArea **area);
diff -r 754959243588 -r 1ce97d0e8823 libexec/lib/src/external_pager.cc
--- a/libexec/lib/src/external_pager.cc	Fri Mar 24 16:14:44 2023 +0100
+++ b/libexec/lib/src/external_pager.cc	Sat Mar 25 18:45:42 2023 +0100
@@ -181,8 +181,8 @@
 
   /* Obtain a region supporting the fault address. */
 
-  MemoryArea *r;
-  long err = _area.find(addr, &r);
+  MemoryArea *r, *parent;
+  long err = _area.find(addr, &r, &parent);
 
   if (!err)
   {
diff -r 754959243588 -r 1ce97d0e8823 libexec/lib/src/internal_pager.cc
--- a/libexec/lib/src/internal_pager.cc	Fri Mar 24 16:14:44 2023 +0100
+++ b/libexec/lib/src/internal_pager.cc	Sat Mar 25 18:45:42 2023 +0100
@@ -101,8 +101,8 @@
 
   /* Obtain a region supporting the fault address. */
 
-  MemoryArea *r;
-  long err = _area.find(addr, &r);
+  MemoryArea *r, *parent;
+  long err = _area.find(addr, &r, &parent);
 
   if (!err)
   {
@@ -170,6 +170,38 @@
   return err;
 }
 
+long InternalPager::detach(address_t addr, address_t size, map_flags_t flags,
+                           address_t *start, address_t *rsize, l4_cap_idx_t *ds)
+{
+  /* Obtain the region supporting the given address.
+     NOTE: All regions within the given range should be detached. */
+
+  MemoryArea *r, *parent;
+  long err = _area.find(addr, &r, &parent);
+
+  if (!err)
+  {
+    *start = r->area_start();
+    *rsize = r->area_end() - r->area_start();
+    *ds = r->dataspace();
+    parent->remove(*r);
+
+    /* Explicitly reply so that the dataspace can be released. */
+
+    complete_RegionMapper_detach(*start, *rsize, *ds);
+
+    /* Free the dataspace reference in this component. Since the same dataspace
+       will have multiple capability indexes, it can be unconditionally
+       released. */
+
+    _dataspaces.erase(*ds);
+    ipc_cap_free_um(*ds);
+    return IPC_MESSAGE_SENT;
+  }
+
+  return err;
+}
+
 long InternalPager::reserve_area(address_t *start, address_t size,
                                  map_flags_t flags, unsigned char align)
 {
diff -r 754959243588 -r 1ce97d0e8823 libexec/lib/src/memory_area.cc
--- a/libexec/lib/src/memory_area.cc	Fri Mar 24 16:14:44 2023 +0100
+++ b/libexec/lib/src/memory_area.cc	Sat Mar 25 18:45:42 2023 +0100
@@ -50,8 +50,13 @@
 
 /* In general, a region supports a memory access within its bounds. */
 
-long MemoryArea::find(address_t addr, MemoryArea **area)
+long MemoryArea::find(address_t addr, MemoryArea **area, MemoryArea **parent)
 {
+  /* The parent is merely propagated through this method, but is present for
+     conformance to the generic method signature. */
+
+  (void) parent;
+
   if ((addr >= _start) && (addr < _end))
   {
     *area = this;
@@ -82,9 +87,10 @@
 
 /* A reserved area does not support any memory access. */
 
-long ReservedMemoryArea::find(address_t addr, MemoryArea **area)
+long ReservedMemoryArea::find(address_t addr, MemoryArea **area,
+                              MemoryArea **parent)
 {
-  (void) addr; (void) area;
+  (void) addr; (void) area; (void) parent;
   return -L4_ENOMEM;
 }
 
@@ -145,7 +151,8 @@
 
 /* Find an region able to support a memory access. */
 
-long AvailableMemoryArea::find(address_t addr, MemoryArea **area)
+long AvailableMemoryArea::find(address_t addr, MemoryArea **area,
+                               MemoryArea **parent)
 {
   MemoryAreaMap::iterator it = _areas.upper_bound(addr);
 
@@ -160,8 +167,10 @@
 
     MemoryArea *r = it->second;
 
+    *parent = this;
+
     if (r->supports(addr))
-      return r->find(addr, area);
+      return r->find(addr, area, parent);
   }
 
   /* Otherwise, no area within this area supports the address. */