[fusil] [PATCH] itrace tool

[Mark Seaborn]

python-ptrace is a useful library - thanks for writing it!

Here is a tool which I have been using to debug libc startup code
where I didn't find gdb very helpful.  It single steps the process and
prints each instruction pointer address.  To go faster, it allows a
number of syscalls to run before starting single-stepping.

It's possible to pipe the addresses through addr2line to get a very
simple tracing debugger. :-)

I couldn't see a way to catch syscalls and single step at the same
time.  As a consequence the tool can't handle multiple threads.

Mark

diff --git a/itrace.py b/itrace.py
new file mode 100755
index 0000000..ce15e9d
--- /dev/null
+++ b/itrace.py
@@ -0,0 +1,43 @@
+#!/usr/bin/env python
+
+import signal
+
+from ptrace.debugger import (PtraceDebugger, Application,
+    ProcessExit, ProcessSignal, NewProcessEvent, ProcessExecution)
+import strace
+
+
+class Tracer(strace.SyscallTracer, object):
+
+    def createCommonOptions(self, parser):
+        parser.add_option(
+            "-n", dest="syscall_limit", type="int", default=None,
+            help="Number of syscalls before switching to single step")
+        super(Tracer, self).createCommonOptions(parser)
+
+    def syscallTrace(self, process):
+        syscall_limit = self.options.syscall_limit
+        i = 0
+        while i < syscall_limit or syscall_limit is None:
+            print i
+            i += 1
+            process.syscall()
+            self.debugger.waitSyscall()
+        i = 0
+        while self.debugger:
+            eip = process.getInstrPointer()
+            print i, process.pid, "[%08x]" % eip
+            i += 1
+            process.singleStep()
+            event = self.debugger.waitProcessEvent()
+            if isinstance(event, ProcessExit):
+                print "process exit"
+                return
+            if (isinstance(event, ProcessSignal) and
+                event.signum & ~128 != signal.SIGTRAP):
+                print "died with signal %i" % event.signum
+                return
+
+
+if __name__ == "__main__":
+    Tracer().main()