Add cfg.cc to hold internal implementation of mem_cfg_t

1 files changed, 23 insertions, 0 deletions

diff --git a/riscv/cfg.cc b/riscv/cfg.cc
new file mode 100644
index 0000000..ef1d579
--- /dev/null
+++ b/riscv/cfg.cc
@@ -0,0 +1,23 @@
+// See LICENSE for license details.
+
+#include "cfg.h"
+#include "mmu.h"
+#include "decode.h"
+
+mem_cfg_t::mem_cfg_t(reg_t base, reg_t size) : base(base), size(size)
+{
+  assert(mem_cfg_t::check_if_supported(base, size));
+}
+
+bool mem_cfg_t::check_if_supported(reg_t base, reg_t size)
+{
+  // The truth of these conditions should be ensured by whatever is creating
+  // the regions in the first place, but we have them here to make sure that
+  // we can't end up describing memory regions that don't make sense. They
+  // ask that the page size is a multiple of the minimum page size, that the
+  // page is aligned to the minimum page size, that the page is non-empty and
+  // that the top address is still representable in a reg_t.
+  return (size % PGSIZE == 0) &&
+         (base % PGSIZE == 0) &&
+         (base + size > base);
+}