Handle misaligned memories by aligning them, rather than erroring

Resolves #442

spike_main/spike.cc

@@ -112,8 +112,23 @@ static std::vector<std::pair<reg_t, mem_t*>> make_mems(const char* arg)
     if (!*p || *p != ':')
       help();
     auto size = strtoull(p + 1, &p, 0);
-    if ((size | base) % PGSIZE != 0)
+
+    // page-align base and size
+    auto base0 = base, size0 = size;
+    size += base0 % PGSIZE;
+    base -= base0 % PGSIZE;
+    if (size % PGSIZE != 0)
+      size += PGSIZE - size % PGSIZE;
+
+    if (base + size < base)
       help();
+
+    if (size != size0) {
+      fprintf(stderr, "Warning: the memory at  [0x%llX, 0x%llX] has been realigned\n"
+                      "to the %ld KiB page size: [0x%llX, 0x%llX]\n",
+              base0, base0 + size0 - 1, PGSIZE / 1024, base, base + size - 1);
+    }
+
     res.push_back(std::make_pair(reg_t(base), new mem_t(size)));
     if (!*p)
       break;