support for the Genode OS framework (#5560)

lib/system/osalloc.nim

@@ -77,6 +77,19 @@ when defined(emscripten):
     var mmapDescr = cast[EmscriptenMMapBlock](mmapDescrPos)
     munmap(mmapDescr.realPointer, mmapDescr.realSize)
 
+elif defined(genode):
+
+  proc osAllocPages(size: int): pointer {.
+   importcpp: "genodeEnv->rm().attach(genodeEnv->ram().alloc(@))".}
+
+  proc osTryAllocPages(size: int): pointer =
+    {.emit: """try {""".}
+    result = osAllocPages size
+    {.emit: """} catch (...) { }""".}
+
+  proc osDeallocPages(p: pointer, size: int) {.
+    importcpp: "genodeEnv->rm().detach(#)".}
+
 elif defined(posix):
   const
     PROT_READ  = 1             # page can be read