Tell gdb we can handle large packets.

This speeds up downloads to 93KB/s, which is starting to get usable.

riscv/gdbserver.cc

@@ -1459,6 +1459,7 @@ void gdbserver_t::handle_query(const std::vector<uint8_t> &packet)
         send("swbreak+;");
       }
     }
+    send("PacketSize=131072;");
     return end_packet();
   }
 

riscv/processor.cc

@@ -204,7 +204,7 @@ void processor_t::enter_debug_mode(uint8_t cause)
   set_privilege(PRV_M);
   state.dpc = state.pc;
   state.pc = DEBUG_ROM_START;
-  debug = true; // TODO
+  //debug = true; // TODO
 }
 
 void processor_t::take_trap(trap_t& t, reg_t epc)

tests/gdbserver.py

@@ -160,7 +160,7 @@ class RegsTest(unittest.TestCase):
 
 class DownloadTest(unittest.TestCase):
     def setUp(self):
-        length = 2**16
+        length = 2**20
         fd = file("data.c", "w")
         fd.write("#include <stdint.h>\n")
         fd.write("uint32_t length = %d;\n" % length)