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.

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

riscv/riscv.mk.in

@@ -14,6 +14,7 @@ riscv_hdrs = \
 	devices.h \
 	dts.h \
 	mmu.h \
+	cfg.h \
 	processor.h \
 	sim.h \
 	simif.h \

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);
   }
 

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;

spike_main/spike.cc

@@ -1,5 +1,6 @@
 // See LICENSE for license details.
 
+#include "cfg.h"
 #include "sim.h"
 #include "mmu.h"
 #include "remote_bitbang.h"
@@ -221,8 +222,6 @@ int main(int argc, char** argv)
   size_t nprocs = 1;
   const char* kernel = NULL;
   reg_t kernel_offset, kernel_size;
-  size_t initrd_size;
-  reg_t initrd_start = 0, initrd_end = 0;
   const char* bootargs = NULL;
   reg_t start_pc = reg_t(-1);
   std::vector<std::pair<reg_t, mem_t*>> mems;
@@ -254,6 +253,7 @@ int main(int argc, char** argv)
     .support_impebreak = true
   };
   std::vector<int> hartids;
+  cfg_t cfg(/*default_initrd_bounds=*/std::make_pair((reg_t)0, (reg_t)0));
 
   auto const hartids_parser = [&](const char *s) {
     std::string const str(s);
@@ -409,11 +409,12 @@ int main(int argc, char** argv)
   }
 
   if (initrd && check_file_exists(initrd)) {
-    initrd_size = get_file_size(initrd);
+    size_t initrd_size = get_file_size(initrd);
     for (auto& m : mems) {
       if (initrd_size && (initrd_size + 0x1000) < m.second->size()) {
-         initrd_end = m.first + m.second->size() - 0x1000;
-         initrd_start = initrd_end - initrd_size;
+         reg_t initrd_end = m.first + m.second->size() - 0x1000;
+         reg_t initrd_start = initrd_end - initrd_size;
+         cfg.initrd_bounds = std::make_pair(initrd_start, initrd_end);
          read_file_bytes(initrd, 0, m.second, initrd_start - m.first, initrd_size);
          break;
       }
@@ -443,8 +444,8 @@ int main(int argc, char** argv)
   }
 #endif
 
-  sim_t s(isa, priv, varch, nprocs, halted, real_time_clint,
-      initrd_start, initrd_end, bootargs, start_pc, mems, plugin_devices, htif_args,
+  sim_t s(&cfg, isa, priv, varch, nprocs, halted, real_time_clint,
+      bootargs, start_pc, mems, plugin_devices, htif_args,
       std::move(hartids), dm_config, log_path, dtb_enabled, dtb_file,
 #ifdef HAVE_BOOST_ASIO
       io_service_ptr, acceptor_ptr,