1 files changed, 119 insertions, 0 deletions
diff --git a/lib/genode/alloc.nim b/lib/genode/alloc.nim
new file mode 100644
index 000000000..52dc1c32c
--- /dev/null
+++ b/lib/genode/alloc.nim
@@ -0,0 +1,119 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2017 Emery Hemingway
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+# Low level dataspace allocator for Genode.
+# For interacting with dataspaces outside of the
+# standard library see the Genode Nimble package.
+
+when not defined(genode):
+  {.error: "Genode only module".}
+
+when not declared(GenodeEnv):
+  include genode/env
+
+type DataspaceCapability {.
+  importcpp: "Genode::Dataspace_capability", pure.} = object
+
+type
+  Map = object
+    attachment: pointer
+    size: int
+    ds: DataspaceCapability
+
+  SlabMeta = object
+    next: ptr MapSlab
+    ds: DataspaceCapability
+
+  MapSlab = object
+    meta: SlabMeta
+    maps: array[1,Map]
+
+const SlabBackendSize = 4096
+
+proc ramAvail(env: GenodeEnv): int {.
+  importcpp: "#->pd().avail_ram().value".}
+  ## Return number of bytes available for allocation.
+
+proc capsAvail(env: GenodeEnv): int {.
+  importcpp: "#->pd().avail_caps().value".}
+  ## Return the number of available capabilities.
+  ## Each dataspace allocation consumes a capability.
+
+proc allocDataspace(env: GenodeEnv; size: int): DataspaceCapability {.
+  importcpp: "#->pd().alloc(@)".}
+  ## Allocate a dataspace and its capability.
+
+proc attachDataspace(env: GenodeEnv; ds: DataspaceCapability): pointer {.
+  importcpp: "#->rm().attach(@)".}
+  ## Attach a dataspace into the component address-space.
+
+proc detachAddress(env: GenodeEnv; p: pointer) {.
+  importcpp: "#->rm().detach(@)".}
+  ## Detach a dataspace from the component address-space.
+
+proc freeDataspace(env: GenodeEnv; ds: DataspaceCapability) {.
+  importcpp: "#->pd().free(@)".}
+  ## Free a dataspace.
+
+proc newMapSlab(): ptr MapSlab =
+  let
+    ds = runtimeEnv.allocDataspace SlabBackendSize
+    p = runtimeEnv.attachDataspace ds
+  result = cast[ptr MapSlab](p)
+  result.meta.ds = ds
+
+iterator items(s: ptr MapSlab): ptr Map =
+  let mapCount = (SlabBackendSize - sizeof(SlabMeta)) div sizeof(Map)
+  for i in 0 .. <mapCount:
+    yield s.maps[i].addr
+
+var slabs: ptr MapSlab
+
+proc osAllocPages(size: int): pointer =
+  if slabs.isNil:
+    slabs = newMapSlab()
+  var
+    slab = slabs
+    map: ptr Map
+  let mapCount = (SlabBackendSize - sizeof(SlabMeta)) div sizeof(Map)
+  block findFreeMap:
+    while true:
+      # lookup first free spot in slabs
+      for m in slab.items:
+        if m.attachment.isNil:
+          map = m
+          break findFreeMap
+      if slab.meta.next.isNil:
+        slab.meta.next = newMapSlab()
+          # tack a new slab on the tail
+      slab = slab.meta.next
+        # move to next slab in linked list
+  map.ds = runtimeEnv.allocDataspace size
+  map.size = size
+  map.attachment = runtimeEnv.attachDataspace map.ds
+  result = map.attachment
+
+proc osTryAllocPages(size: int): pointer =
+  if runtimeEnv.ramAvail() >= size and runtimeEnv.capsAvail() > 4:
+    result = osAllocPages size
+
+proc osDeallocPages(p: pointer; size: int) =
+  var slab = slabs
+  while not slab.isNil:
+    # lookup first free spot in slabs
+    for m in slab.items:
+      if m.attachment == p:
+        if m.size != size:
+          echo "cannot partially detach dataspace"
+          quit -1
+        runtimeEnv.detachAddress m.attachment
+        runtimeEnv.freeDataspace m.ds
+        m[] = Map()
+        return
+    slab = slab.meta.next