Add debug module authentication.

Off by default, enabled with --debug-auth.
The protocol is very simple (definitely not secure) to allow debuggers
to test their authentication feature. To authenticate a debugger must:
1. Read authdata
2. Write to authdata the value that it just read, plus 1

1 files changed, 7 insertions, 3 deletions

diff --git a/spike_main/spike.cc b/spike_main/spike.cc
index f77d488..eb57baf 100644
--- a/spike_main/spike.cc
+++ b/spike_main/spike.cc
@@ -36,9 +36,10 @@ static void help()
   fprintf(stderr, "  --extlib=<name>       Shared library to load\n");
   fprintf(stderr, "  --rbb-port=<port>     Listen on <port> for remote bitbang connection\n");
   fprintf(stderr, "  --dump-dts            Print device tree string and exit\n");
-  fprintf(stderr, "  --progsize=<words>    progsize for the debug module [default 2]\n");
-  fprintf(stderr, "  --debug-sba=<bits>    debug bus master supports up to "
+  fprintf(stderr, "  --progsize=<words>    Progsize for the debug module [default 2]\n");
+  fprintf(stderr, "  --debug-sba=<bits>    Debug bus master supports up to "
       "<bits> wide accesses [default 0]\n");
+  fprintf(stderr, "  --debug-auth          Debug module requires debugger to authenticate\n");
   exit(1);
 }
 
@@ -92,6 +93,7 @@ int main(int argc, char** argv)
   bool use_rbb = false;
   unsigned progsize = 2;
   unsigned max_bus_master_bits = 0;
+  bool require_authentication = false;
   std::vector<int> hartids;
 
   auto const hartids_parser = [&](const char *s) {
@@ -135,6 +137,8 @@ int main(int argc, char** argv)
   parser.option(0, "progsize", 1, [&](const char* s){progsize = atoi(s);});
   parser.option(0, "debug-sba", 1,
       [&](const char* s){max_bus_master_bits = atoi(s);});
+  parser.option(0, "debug-auth", 0,
+      [&](const char* s){require_authentication = true;});
 
   auto argv1 = parser.parse(argv);
   std::vector<std::string> htif_args(argv1, (const char*const*)argv + argc);
@@ -142,7 +146,7 @@ int main(int argc, char** argv)
     mems = make_mems("2048");
 
   sim_t s(isa, nprocs, halted, start_pc, mems, htif_args, std::move(hartids),
-      progsize, max_bus_master_bits);
+      progsize, max_bus_master_bits, require_authentication);
   std::unique_ptr<remote_bitbang_t> remote_bitbang((remote_bitbang_t *) NULL);
   std::unique_ptr<jtag_dtm_t> jtag_dtm(new jtag_dtm_t(&s.debug_module));
   if (use_rbb) {