Improve pwnup template, gdbserver detection (#1148)

* Improve pwnup template

* Don't want to break at main again if its been hit already

* Always start the program

* Handle extra newline printed by gdb

* Remove moved recvline

* Remove controversial set sysroot

* Update gdb.py

* Update pwnup.mako

pwnlib/data/templates/pwnup.mako

@@ -132,9 +132,9 @@ def start(argv=[], *a, **kw):
 gdbscript = '''
 %if ctx.binary:
   %if 'main' in ctx.binary.symbols:
-break *0x{exe.symbols.main:x}
-  %else:
-break *0x{exe.entry:x}
+tbreak main
+  %elif 'DYN' != ctx.binary.elftype:
+tbreak *0x{exe.entry:x}
   %endif
 %endif
 continue

pwnlib/gdb.py

@@ -464,9 +464,9 @@ def debug(args, gdbscript=None, exe=None, ssh=None, env=None, sysroot=None, **kw
 
     # gdbserver outputs a message when a client connects
     garbage = gdbserver.recvline(timeout=1)
-
-    if "Remote debugging from host" not in garbage:
-        gdbserver.unrecv(garbage)
+    
+    # Some versions of gdbserver output an additional message
+    garbage2 = gdbserver.recvline_startswith("Remote debugging from host ", timeout=1)
 
     return gdbserver