Improve debugging experience (#10)

* Fix crash on second CTRL+C
* Download gdb-dashboard automatically
* Stub for downloading files from remote side
* gdb: use monitor command to interact with fs-uae debugger
* Comment how to use monitor command

.gdbinit

@@ -6,5 +6,19 @@ set verbose off
 
 source gdb-dashboard
 dashboard -layout breakpoints assembly registers source stack variables
-# Please refer to https://github.com/cyrus-and/gdb-dashboard/wiki to learn how to customize visual experience
+# Please refer to https://github.com/cyrus-and/gdb-dashboard/wiki
+# to learn how to customize visual experience
 dashboard -style style_low '2'
+
+# Use `monitor` command to access fs-uae debugger.
+# Type `monitor ?` to see the list of available commands.
+# Some useful commands are:
+# * `v -3` - turn on visual DMA debugger
+# * `vo` - turn off visual DMA debugger
+# * `o 1` - display and disassembly current copper list
+# * `c` - display state of CIA registers
+# * `e` - display state of custom registers
+
+# Please use fs-uae debugger carefully - preferably only for inspecting state of
+# the machine. It's a very powerful tool but even mistyping a command can break
+# a session between gdb and the emulator.

Makefile

@@ -18,3 +18,6 @@ tags:
 
 cscope.out:
 	cscope -b $(FILES)
+
+gdb-dashboard:
+	wget -O $@ https://raw.githubusercontent.com/cyrus-and/gdb-dashboard/master/.gdbinit

build/effect.mk

@@ -84,14 +84,17 @@ DEBUGGER ?= gdb
 run-floppy: $(EFFECT).exe.dbg $(EFFECT).adf
 	$(LAUNCH) -e $(EFFECT).exe.dbg -f $(EFFECT).adf
 
-debug-floppy: $(EFFECT).exe.dbg $(EFFECT).adf
+debug-floppy: $(EFFECT).exe.dbg $(EFFECT).adf $(TOPDIR)/gdb-dashboard
 	$(LAUNCH) -d $(DEBUGGER) -f $(EFFECT).adf -e $(EFFECT).exe.dbg
 
 run: $(EFFECT).rom $(EFFECT).exe.dbg $(EFFECT).adf
 	$(LAUNCH) -r $(EFFECT).rom -e $(EFFECT).exe.dbg -f $(EFFECT).adf
 
-debug: $(EFFECT).rom $(EFFECT).exe.dbg $(EFFECT).adf
+debug: $(EFFECT).rom $(EFFECT).exe.dbg $(EFFECT).adf $(TOPDIR)/gdb-dashboard
 	$(LAUNCH) -d $(DEBUGGER) -r $(EFFECT).rom -e $(EFFECT).exe.dbg -f $(EFFECT).adf
 
+$(TOPDIR)/gdb-dashboard:
+	make -C $(TOPDIR) gdb-dashboard
+
 .PHONY: run debug run-floppy debug-floppy
 .PRECIOUS: $(BOOTLOADER) $(EFFECT).img

tools/debug/gdb.py

@@ -141,9 +141,30 @@ async def handle_query(self, packet):
             # Notify the target that GDB is prepared to serve symbol
             # lookup requests.
             self.gdb.send_ack('OK')
+        elif packet.startswith('Rcmd,'):
+            # Forwards input from `monitor` command to UAE debugger.
+            raw_cmd = packet.split(',', maxsplit=1)[1]
+            cmd = bytes.fromhex(raw_cmd).decode('utf-8')
+            lines = await self.uae.communicate(cmd)
+            text = '\n'.join(lines) + '\n'
+            self.gdb.send_ack(text.encode('utf-8').hex())
 
         return True
 
+    def handle_file(self, packet):
+        # Minimal support for `remote get` command to transfer empty files.
+        cmd, args = packet[0], packet[1].split(',')
+        if cmd == 'setfs':
+            self.gdb.send_ack('F0')
+        elif cmd == 'open':
+            self.gdb.send_ack('F0')
+        elif cmd == 'close':
+            self.gdb.send_ack('F0')
+        elif cmd == 'pread':
+            self.gdb.send_ack('F0;')  # `pread` command requires semicolon
+        else:
+            self.gdb.send_ack('')
+
     @staticmethod
     def binary_decode(data):
         # Decode GDB binary stream. See:
@@ -281,7 +302,10 @@ async def handle_packet(self, packet):
         elif packet[0] == 'v':
             # The correct reply to an unknown 'v' packet is to return the
             # empty string.
-            self.gdb.send_ack('')
+            if packet.startswith('vFile:'):
+                self.handle_file(packet.split(':')[1:])
+            else:
+                self.gdb.send_ack('')
 
         return True
 

tools/debug/uae.py

@@ -272,6 +272,10 @@ async def kill(self):
 
 
 async def UaeDebugger(uaedbg):
+    # Call FS-UAE debugger on CTRL+C
+    loop = asyncio.get_event_loop()
+    loop.add_signal_handler(signal.SIGINT, uaedbg.interrupt)
+
     history = InMemoryHistory()
     session = PromptSession('(debug) ', history=history)
     with patch_stdout():
@@ -285,6 +289,9 @@ async def UaeDebugger(uaedbg):
                     while not cmd:
                         cmd = await session.prompt_async()
                         cmd.strip()
+                        # prompt_async removes our SIGINT handler :(
+                        loop.add_signal_handler(signal.SIGINT,
+                                                uaedbg.interrupt)
                     uaedbg.send(cmd)
                 except EOFError:
                     uaedbg.resume()

tools/uaedbg.py

@@ -51,8 +51,6 @@ async def GdbListen():
     if args.gdbserver:
         await GdbListen()
     else:
-        # Call FS-UAE debugger on CTRL+C
-        loop.add_signal_handler(signal.SIGINT, uaeproc.interrupt)
         prompt_task = asyncio.ensure_future(UaeDebugger(uaeproc))
 
     await uaeproc.wait()
@@ -70,9 +68,9 @@ async def GdbListen():
 
     if sys.platform == 'win32':
         loop = asyncio.ProactorEventLoop()
-        asyncio.set_event_loop(loop)
     else:
-        loop = asyncio.get_event_loop()
+        loop = asyncio.SelectorEventLoop()
+    asyncio.set_event_loop(loop)
     # loop.set_debug(True)
 
     parser = argparse.ArgumentParser(