Split mem layout computation in spike.cc (#957)

The motivation here is mostly to enable a refactoring where the memory
layout (sans allocated memory) gets passed to DTS/DTB code before we
ever allocate anything.

But it turns out to make merge_overlapping_memory_regions a bit
simpler, which is an added bonus.

1 files changed, 29 insertions, 2 deletions

diff --git a/riscv/cfg.h b/riscv/cfg.h
index f0dea9f..e844738 100644
--- a/riscv/cfg.h
+++ b/riscv/cfg.h
@@ -3,6 +3,8 @@
 #define _RISCV_CFG_H
 
 #include "decode.h"
+#include "mmu.h"
+#include <cassert>
 
 template <typename T>
 class cfg_arg_t {
@@ -25,17 +27,41 @@ private:
   bool was_set;
 };
 
+// Configuration that describes a memory region
+class mem_cfg_t
+{
+public:
+  mem_cfg_t(reg_t base, reg_t size)
+    : base(base), size(size)
+  {
+    // The truth of these assertions 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.
+    assert((size % PGSIZE == 0) &&
+           (base % PGSIZE == 0) &&
+           (base + size > base));
+  }
+
+  reg_t base;
+  reg_t size;
+};
+
 class cfg_t
 {
 public:
   cfg_t(std::pair<reg_t, reg_t> default_initrd_bounds,
         const char *default_bootargs, size_t default_nprocs,
-        const char *default_isa, const char *default_priv)
+        const char *default_isa, const char *default_priv,
+        const std::vector<mem_cfg_t> &default_mem_layout)
     : initrd_bounds(default_initrd_bounds),
       bootargs(default_bootargs),
       nprocs(default_nprocs),
       isa(default_isa),
-      priv(default_priv)
+      priv(default_priv),
+      mem_layout(default_mem_layout)
   {}
 
   cfg_arg_t<std::pair<reg_t, reg_t>> initrd_bounds;
@@ -43,6 +69,7 @@ public:
   cfg_arg_t<size_t>                  nprocs;
   cfg_arg_t<const char *>            isa;
   cfg_arg_t<const char *>            priv;
+  cfg_arg_t<std::vector<mem_cfg_t>>  mem_layout;
 };
 
 #endif