Initial step towards factoring out command line configuration

This commit defines a "cfg_t" structure, which currently just holds
the initrd address range. It will be augmented in future commits to
hold other configuration arguments as well.

To represent a configuration argument, we define an arg_t base class.
This holds a current value, together with a flag that tells us whether
the value has been updated from the default. The idea is that in
future we're going to use that flag when reading a DTB file: if an
argument has actually been specified on the command line, we need to
take it into account; if not, we can ignore the default and use the
DTB file's supplied value.

4 files changed, 53 insertions, 11 deletions

diff --git a/riscv/cfg.h b/riscv/cfg.h
new file mode 100644
index 0000000..bee5051
--- /dev/null
+++ b/riscv/cfg.h
@@ -0,0 +1,38 @@
+// See LICENSE for license details.
+#ifndef _RISCV_CFG_H
+#define _RISCV_CFG_H
+
+#include "decode.h"
+
+template <typename T>
+class cfg_arg_t {
+public:
+  cfg_arg_t(T default_val)
+    : value(default_val), was_set(false) {}
+
+  bool overridden() const { return was_set; }
+
+  T operator()() const { return value; }
+
+  T operator=(const T v) {
+    value = v;
+    was_set = true;
+    return value;
+  }
+
+private:
+  T value;
+  bool was_set;
+};
+
+class cfg_t
+{
+public:
+  cfg_t(std::pair<reg_t, reg_t> default_initrd_bounds)
+    : initrd_bounds(default_initrd_bounds)
+  {}
+
+  cfg_arg_t<std::pair<reg_t, reg_t>> initrd_bounds;
+};
+
+#endif
diff --git a/riscv/riscv.mk.in b/riscv/riscv.mk.in
index a160bb8..a803b2a 100644
--- a/riscv/riscv.mk.in
+++ b/riscv/riscv.mk.in
@@ -14,6 +14,7 @@ riscv_hdrs = \
 	devices.h \
 	dts.h \
 	mmu.h \
+	cfg.h \
 	processor.h \
 	sim.h \
 	simif.h \
diff --git a/riscv/sim.cc b/riscv/sim.cc
index 064a493..9bfa17a 100644
--- a/riscv/sim.cc
+++ b/riscv/sim.cc
@@ -28,9 +28,9 @@ static void handle_signal(int sig)
   signal(sig, &handle_signal);
 }
 
-sim_t::sim_t(const char* isa_string, const char* priv, const char* varch,
-             size_t nprocs, bool halted, bool real_time_clint,
-             reg_t initrd_start, reg_t initrd_end, const char* bootargs,
+sim_t::sim_t(const cfg_t *cfg,
+             const char* isa_string, const char* priv, const char* varch,
+             size_t nprocs, bool halted, bool real_time_clint, const char* bootargs,
              reg_t start_pc, std::vector<std::pair<reg_t, mem_t*>> mems,
              std::vector<std::pair<reg_t, abstract_device_t*>> plugin_devices,
              const std::vector<std::string>& args,
@@ -44,11 +44,10 @@ sim_t::sim_t(const char* isa_string, const char* priv, const char* varch,
              FILE *cmd_file) // needed for command line option --cmd
   : htif_t(args),
     isa(isa_string, priv),
+    cfg(cfg),
     mems(mems),
     plugin_devices(plugin_devices),
     procs(std::max(nprocs, size_t(1))),
-    initrd_start(initrd_start),
-    initrd_end(initrd_end),
     bootargs(bootargs),
     start_pc(start_pc),
     dtb_file(dtb_file ? dtb_file : ""),
@@ -312,7 +311,10 @@ void sim_t::make_dtb()
 
     dtb = strstream.str();
   } else {
-    dts = make_dts(INSNS_PER_RTC_TICK, CPU_HZ, initrd_start, initrd_end, bootargs, procs, mems);
+    std::pair<reg_t, reg_t> initrd_bounds = cfg->initrd_bounds();
+    dts = make_dts(INSNS_PER_RTC_TICK, CPU_HZ,
+                   initrd_bounds.first, initrd_bounds.second,
+                   bootargs, procs, mems);
     dtb = dts_compile(dts);
   }
 
diff --git a/riscv/sim.h b/riscv/sim.h
index 518d75e..31c9254 100644
--- a/riscv/sim.h
+++ b/riscv/sim.h
@@ -11,6 +11,7 @@
 #include <boost/asio.hpp>
 #endif
 
+#include "cfg.h"
 #include "debug_module.h"
 #include "devices.h"
 #include "log_file.h"
@@ -31,9 +32,9 @@ class remote_bitbang_t;
 class sim_t : public htif_t, public simif_t
 {
 public:
-  sim_t(const char* isa, const char* priv, const char* varch, size_t _nprocs,
-        bool halted, bool real_time_clint,
-        reg_t initrd_start, reg_t initrd_end, const char* bootargs,
+  sim_t(const cfg_t *cfg,
+        const char* isa, const char* priv, const char* varch, size_t _nprocs,
+        bool halted, bool real_time_clint, const char* bootargs,
         reg_t start_pc, std::vector<std::pair<reg_t, mem_t*>> mems,
         std::vector<std::pair<reg_t, abstract_device_t*>> plugin_devices,
         const std::vector<std::string>& args, const std::vector<int> hartids,
@@ -71,12 +72,12 @@ public:
 
 private:
   isa_parser_t isa;
+  const cfg_t * const cfg;
   std::vector<std::pair<reg_t, mem_t*>> mems;
   std::vector<std::pair<reg_t, abstract_device_t*>> plugin_devices;
   mmu_t* debug_mmu;  // debug port into main memory
   std::vector<processor_t*> procs;
-  reg_t initrd_start;
-  reg_t initrd_end;
+  std::pair<reg_t, reg_t> initrd_range;
   const char* bootargs;
   reg_t start_pc;
   std::string dts;