src/pkg/runtime/runtime-gdb.py - go - Git at Google

 # Copyright 2010 The Go Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.

 """GDB Pretty printers and convenience functions for Go's runtime structures.

 This script is loaded by GDB when it finds a .debug_gdb_scripts
 section in the compiled binary.  The [68]l linkers emit this with a
 path to this file based on the path to the runtime package.
 """

 # Known issues:
 #    - pretty printing only works for the 'native' strings. E.g. 'type
 #      foo string' will make foo a plain struct in the eyes of gdb,
 #      circumventing the pretty print triggering.


 import sys, re

 print >>sys.stderr, "Loading Go Runtime support."

 # allow to manually reload while developing
 goobjfile = gdb.current_objfile() or gdb.objfiles()[0]
 goobjfile.pretty_printers = []

 #
 #  Pretty Printers
 #

 class StringTypePrinter:
 	"Pretty print Go strings."

 	pattern = re.compile(r'^struct string$')

 	def __init__(self, val):
 		self.val = val

 	def display_hint(self):
 		return 'string'

 	def to_string(self):
 		l = int(self.val['len'])
 		return self.val['str'].string("utf-8", "ignore", l)


 class SliceTypePrinter:
 	"Pretty print slices."

 	pattern = re.compile(r'^struct \[\]')

 	def __init__(self, val):
 		self.val = val

 	def display_hint(self):
 		return 'array'

 	def to_string(self):
 		return str(self.val.type)[6:]  # skip 'struct '

 	def children(self):
 		ptr = self.val["array"]
 		for idx in range(self.val["len"]):
 			yield ('[%d]' % idx, (ptr + idx).dereference())


 class MapTypePrinter:
 	"""Pretty print map[K]V types.

 	Map-typed go variables are really pointers. dereference them in gdb
 	to inspect their contents with this pretty printer.
 	"""

 	pattern = re.compile(r'^struct hash<.*>$')

 	def __init__(self, val):
 		self.val = val

 	def display_hint(self):
 		return 'map'

 	def to_string(self):
 		return str(self.val.type)

 	def children(self):
 		stab = self.val['st']
 		i = 0
 		for v in self.traverse_hash(stab):
 			yield ("[%d]" %  i, v['key'])
 			yield ("[%d]" % (i + 1), v['val'])
 			i += 2

 	def traverse_hash(self, stab):
 		ptr = stab['entry'].address
 		last = stab['last']
 		while ptr <= last:
 			v = ptr.dereference()
 			ptr = ptr + 1
 			if v['hash'] == 0: continue
 			if v['hash'] & 63 == 63:   # subtable
 				for v in self.traverse_hash(v['key'].cast(self.val['st'].type)):
 					yield v
 			else:
 				yield v


 class ChanTypePrinter:
 	"""Pretty print chan[T] types.

 	Chan-typed go variables are really pointers. dereference them in gdb
 	to inspect their contents with this pretty printer.
 	"""

 	pattern = re.compile(r'^struct hchan<.*>$')

 	def __init__(self, val):
 		self.val = val

 	def display_hint(self):
 		return 'array'

 	def to_string(self):
 		return str(self.val.type)

 	def children(self):
 		# see chan.c chanbuf().  et is the type stolen from hchan<T>::recvq->first->elem
 		et = [x.type for x in self.val['recvq']['first'].type.target().fields() if x.name == 'elem'][0]
                 ptr = (self.val.address + 1).cast(et.pointer())
                 for i in range(self.val["qcount"]):
 			j = (self.val["recvx"] + i) % self.val["dataqsiz"]
 			yield ('[%d]' % i, (ptr + j).dereference())


 #
 #  Register all the *Printer classes above.
 #

 def makematcher(klass):
 	def matcher(val):
 		try:
 			if klass.pattern.match(str(val.type)):
 				return klass(val)
 		except:
 			pass
 	return matcher

 goobjfile.pretty_printers.extend([makematcher(k) for k in vars().values() if hasattr(k, 'pattern')])

 #
 #  For reference, this is what we're trying to do:
 #  eface: p *(*(struct 'runtime.commonType'*)'main.e'->type_->data)->string
 #  iface: p *(*(struct 'runtime.commonType'*)'main.s'->tab->Type->data)->string
 #
 # interface types can't be recognized by their name, instead we check
 # if they have the expected fields.  Unfortunately the mapping of
 # fields to python attributes in gdb.py isn't complete: you can't test
 # for presence other than by trapping.


 def is_iface(val):
 	try:
 		return str(val['tab'].type) == "struct runtime.itab *" \
 		      and str(val['data'].type) == "void *"
 	except:
 		pass

 def is_eface(val):
 	try:
 		return str(val['_type'].type) == "struct runtime._type *" \
 		      and str(val['data'].type) == "void *"
 	except:
 		pass

 def lookup_type(name):
 	try:
 		return gdb.lookup_type(name)
 	except:
 		pass
 	try:
 		return gdb.lookup_type('struct ' + name)
 	except:
 		pass
 	try:
 		return gdb.lookup_type('struct ' + name[1:]).pointer()
 	except:
 		pass


 def iface_dtype(obj):
 	"Decode type of the data field of an eface or iface struct."
         # known issue: dtype_name decoded from runtime.commonType is "nested.Foo"
         # but the dwarf table lists it as "full/path/to/nested.Foo"

 	if is_iface(obj):
 		go_type_ptr = obj['tab']['_type']
 	elif is_eface(obj):
 		go_type_ptr = obj['_type']
 	else:
 		return

 	ct = gdb.lookup_type("struct runtime.commonType").pointer()
 	dynamic_go_type = go_type_ptr['ptr'].cast(ct).dereference()
 	dtype_name = dynamic_go_type['string'].dereference()['str'].string()

 	dynamic_gdb_type = lookup_type(dtype_name)
         if dynamic_gdb_type:
 		type_size = int(dynamic_go_type['size'])
                 uintptr_size = int(dynamic_go_type['size'].type.sizeof)  # size is itself an uintptr
 		if type_size > uintptr_size:
 			dynamic_gdb_type = dynamic_gdb_type.pointer()

 	return dynamic_gdb_type

 def iface_dtype_name(obj):
 	"Decode type name of the data field of an eface or iface struct."

 	if is_iface(obj):
 		go_type_ptr = obj['tab']['_type']
 	elif is_eface(obj):
 		go_type_ptr = obj['_type']
 	else:
 		return

 	ct = gdb.lookup_type("struct runtime.commonType").pointer()
 	dynamic_go_type = go_type_ptr['ptr'].cast(ct).dereference()
 	return dynamic_go_type['string'].dereference()['str'].string()


 class IfacePrinter:
 	"""Pretty print interface values

 	Casts the data field to the appropriate dynamic type."""

 	def __init__(self, val):
 		self.val = val

 	def display_hint(self):
 		return 'string'

 	def to_string(self):
 		if self.val['data'] == 0:
 			return 0x0
 		try:
 			dtype = iface_dtype(self.val)
 		except:
 			return "<bad dynamic type>"

                 if not dtype:  # trouble looking up, print something reasonable
 			return "(%s)%s" % (iface_dtype_name(self.val), self.val['data'])

 		try:
 			return self.val['data'].cast(dtype).dereference()
 		except:
 			pass
 		return self.val['data'].cast(dtype)


 def ifacematcher(val):
 	if is_iface(val) or is_eface(val):
 		return IfacePrinter(val)

 goobjfile.pretty_printers.append(ifacematcher)

 #
 #  Convenience Functions
 #

 class GoLenFunc(gdb.Function):
 	"Length of strings, slices, maps or channels"

 	how = ((StringTypePrinter, 'len' ),
 	       (SliceTypePrinter, 'len'),
 	       (MapTypePrinter, 'count'),
 	       (ChanTypePrinter, 'qcount'))

 	def __init__(self):
 		super(GoLenFunc, self).__init__("len")

 	def invoke(self, obj):
 		typename = str(obj.type)
 		for klass, fld in self.how:
 			if klass.pattern.match(typename):
 				return obj[fld]

 class GoCapFunc(gdb.Function):
 	"Capacity of slices or channels"

 	how = ((SliceTypePrinter, 'cap'),
 	       (ChanTypePrinter, 'dataqsiz'))

 	def __init__(self):
 		super(GoCapFunc, self).__init__("cap")

 	def invoke(self, obj):
 		typename = str(obj.type)
 		for klass, fld in self.how:
 			if klass.pattern.match(typename):
 				return obj[fld]

 class DTypeFunc(gdb.Function):
 	"""Cast Interface values to their dynamic type.

 	For non-interface types this behaves as the identity operation.
 	"""

 	def __init__(self):
 		super(DTypeFunc, self).__init__("dtype")

 	def invoke(self, obj):
 		try:
 			return obj['data'].cast(iface_dtype(obj))
 		except:
 			pass
 		return obj

 #
 #  Commands
 #

 sts = ( 'idle', 'runnable', 'running', 'syscall', 'waiting', 'moribund', 'dead', 'recovery')

 def linked_list(ptr, linkfield):
 	while ptr:
 		yield ptr
 		ptr = ptr[linkfield]


 class GoroutinesCmd(gdb.Command):
 	"List all goroutines."

 	def __init__(self):
 		super(GoroutinesCmd, self).__init__("info goroutines", gdb.COMMAND_STACK, gdb.COMPLETE_NONE)

 	def invoke(self, arg, from_tty):
 		# args = gdb.string_to_argv(arg)
 		vp = gdb.lookup_type('void').pointer()
 		for ptr in linked_list(gdb.parse_and_eval("'runtime.allg'"), 'alllink'):
 			if ptr['status'] == 6:	# 'gdead'
 				continue
 			s = ' '
 			if ptr['m']:
 				s = '*'
                         pc = ptr['sched']['pc'].cast(vp)
                         sp = ptr['sched']['sp'].cast(vp)
 			blk = gdb.block_for_pc(long((pc)))
 			print s, ptr['goid'], "%8s" % sts[long((ptr['status']))], blk.function

 def find_goroutine(goid):
 	vp = gdb.lookup_type('void').pointer()
 	for ptr in linked_list(gdb.parse_and_eval("'runtime.allg'"), 'alllink'):
 		if ptr['status'] == 6:	# 'gdead'
 			continue
 		if ptr['goid'] == goid:
 			return [ptr['sched'][x].cast(vp) for x in 'pc', 'sp']
 	return None, None


 class GoroutineCmd(gdb.Command):
 	"""Execute gdb command in the context of goroutine <goid>.

 	Switch PC and SP to the ones in the goroutine's G structure,
 	execute an arbitrary gdb command, and restore PC and SP.

 	Usage: (gdb) goroutine <goid> <gdbcmd>

 	Note that it is ill-defined to modify state in the context of a goroutine.
 	Restrict yourself to inspecting values.
 	"""

 	def __init__(self):
 		super(GoroutineCmd, self).__init__("goroutine", gdb.COMMAND_STACK, gdb.COMPLETE_NONE)

 	def invoke(self, arg, from_tty):
 		goid, cmd = arg.split(None, 1)
 		pc, sp = find_goroutine(int(goid))
 		if not pc:
 			print "No such goroutine: ", goid
 			return
 		save_frame = gdb.selected_frame()
 		gdb.parse_and_eval('$save_pc = $pc')
 		gdb.parse_and_eval('$save_sp = $sp')
 		gdb.parse_and_eval('$pc = 0x%x' % long(pc))
 		gdb.parse_and_eval('$sp = 0x%x' % long(sp))
 		try:
 			gdb.execute(cmd)
                 finally:
 			gdb.parse_and_eval('$pc = $save_pc')
                         gdb.parse_and_eval('$sp = $save_sp')
                         save_frame.select()


 class GoIfaceCmd(gdb.Command):
 	"Print Static and dynamic interface types"

 	def __init__(self):
 		super(GoIfaceCmd, self).__init__("iface", gdb.COMMAND_DATA, gdb.COMPLETE_SYMBOL)

 	def invoke(self, arg, from_tty):
 		for obj in gdb.string_to_argv(arg):
 			try:
 				#TODO fix quoting for qualified variable names
 				obj = gdb.parse_and_eval("%s" % obj)
 			except Exception, e:
 				print "Can't parse ", obj, ": ", e
 				continue

 			dtype = iface_dtype(obj)
 			if not dtype:
 				print "Not an interface: ", obj.type
 				continue

 			print "%s: %s" % (obj.type, dtype)

 # TODO: print interface's methods and dynamic type's func pointers thereof.
 #rsc: "to find the number of entries in the itab's Fn field look at itab.inter->numMethods
 #i am sure i have the names wrong but look at the interface type and its method count"
 # so Itype will start with a commontype which has kind = interface

 #
 # Register all convenience functions and CLI commands
 #
 for k in vars().values():
 	if hasattr(k, 'invoke'):
 		k()
	# Copyright 2010 The Go Authors. All rights reserved.
	# Use of this source code is governed by a BSD-style
	# license that can be found in the LICENSE file.

	"""GDB Pretty printers and convenience functions for Go's runtime structures.

	This script is loaded by GDB when it finds a .debug_gdb_scripts
	section in the compiled binary. The [68]l linkers emit this with a
	path to this file based on the path to the runtime package.
	"""

	# Known issues:
	# - pretty printing only works for the 'native' strings. E.g. 'type
	# foo string' will make foo a plain struct in the eyes of gdb,
	# circumventing the pretty print triggering.


	import sys, re

	print >>sys.stderr, "Loading Go Runtime support."

	# allow to manually reload while developing
	goobjfile = gdb.current_objfile() or gdb.objfiles()[0]
	goobjfile.pretty_printers = []

	#
	# Pretty Printers
	#

	class StringTypePrinter:
	"Pretty print Go strings."

	pattern = re.compile(r'^struct string$')

	def __init__(self, val):
	self.val = val

	def display_hint(self):
	return 'string'

	def to_string(self):
	l = int(self.val['len'])
	return self.val['str'].string("utf-8", "ignore", l)


	class SliceTypePrinter:
	"Pretty print slices."

	pattern = re.compile(r'^struct \[\]')

	def __init__(self, val):
	self.val = val

	def display_hint(self):
	return 'array'

	def to_string(self):
	return str(self.val.type)[6:] # skip 'struct '

	def children(self):
	ptr = self.val["array"]
	for idx in range(self.val["len"]):
	yield ('[%d]' % idx, (ptr + idx).dereference())


	class MapTypePrinter:
	"""Pretty print map[K]V types.

	Map-typed go variables are really pointers. dereference them in gdb
	to inspect their contents with this pretty printer.
	"""

	pattern = re.compile(r'^struct hash<.*>$')

	def __init__(self, val):
	self.val = val

	def display_hint(self):
	return 'map'

	def to_string(self):
	return str(self.val.type)

	def children(self):
	stab = self.val['st']
	i = 0
	for v in self.traverse_hash(stab):
	yield ("[%d]" % i, v['key'])
	yield ("[%d]" % (i + 1), v['val'])
	i += 2

	def traverse_hash(self, stab):
	ptr = stab['entry'].address
	last = stab['last']
	while ptr <= last:
	v = ptr.dereference()
	ptr = ptr + 1
	if v['hash'] == 0: continue
	if v['hash'] & 63 == 63: # subtable
	for v in self.traverse_hash(v['key'].cast(self.val['st'].type)):
	yield v
	else:
	yield v


	class ChanTypePrinter:
	"""Pretty print chan[T] types.

	Chan-typed go variables are really pointers. dereference them in gdb
	to inspect their contents with this pretty printer.
	"""

	pattern = re.compile(r'^struct hchan<.*>$')

	def __init__(self, val):
	self.val = val

	def display_hint(self):
	return 'array'

	def to_string(self):
	return str(self.val.type)

	def children(self):
	# see chan.c chanbuf(). et is the type stolen from hchan<T>::recvq->first->elem
	et = [x.type for x in self.val['recvq']['first'].type.target().fields() if x.name == 'elem'][0]
	ptr = (self.val.address + 1).cast(et.pointer())
	for i in range(self.val["qcount"]):
	j = (self.val["recvx"] + i) % self.val["dataqsiz"]
	yield ('[%d]' % i, (ptr + j).dereference())


	#
	# Register all the *Printer classes above.
	#

	def makematcher(klass):
	def matcher(val):
	try:
	if klass.pattern.match(str(val.type)):
	return klass(val)
	except:
	pass
	return matcher

	goobjfile.pretty_printers.extend([makematcher(k) for k in vars().values() if hasattr(k, 'pattern')])

	#
	# For reference, this is what we're trying to do:
	# eface: p ((struct 'runtime.commonType'*)'main.e'->type_->data)->string
	# iface: p ((struct 'runtime.commonType'*)'main.s'->tab->Type->data)->string
	#
	# interface types can't be recognized by their name, instead we check
	# if they have the expected fields. Unfortunately the mapping of
	# fields to python attributes in gdb.py isn't complete: you can't test
	# for presence other than by trapping.


	def is_iface(val):
	try:
	return str(val['tab'].type) == "struct runtime.itab *" \
	and str(val['data'].type) == "void *"
	except:
	pass

	def is_eface(val):
	try:
	return str(val['_type'].type) == "struct runtime._type *" \
	and str(val['data'].type) == "void *"
	except:
	pass

	def lookup_type(name):
	try:
	return gdb.lookup_type(name)
	except:
	pass
	try:
	return gdb.lookup_type('struct ' + name)
	except:
	pass
	try:
	return gdb.lookup_type('struct ' + name[1:]).pointer()
	except:
	pass


	def iface_dtype(obj):
	"Decode type of the data field of an eface or iface struct."
	# known issue: dtype_name decoded from runtime.commonType is "nested.Foo"
	# but the dwarf table lists it as "full/path/to/nested.Foo"

	if is_iface(obj):
	go_type_ptr = obj['tab']['_type']
	elif is_eface(obj):
	go_type_ptr = obj['_type']
	else:
	return

	ct = gdb.lookup_type("struct runtime.commonType").pointer()
	dynamic_go_type = go_type_ptr['ptr'].cast(ct).dereference()
	dtype_name = dynamic_go_type['string'].dereference()['str'].string()

	dynamic_gdb_type = lookup_type(dtype_name)
	if dynamic_gdb_type:
	type_size = int(dynamic_go_type['size'])
	uintptr_size = int(dynamic_go_type['size'].type.sizeof) # size is itself an uintptr
	if type_size > uintptr_size:
	dynamic_gdb_type = dynamic_gdb_type.pointer()

	return dynamic_gdb_type

	def iface_dtype_name(obj):
	"Decode type name of the data field of an eface or iface struct."

	if is_iface(obj):
	go_type_ptr = obj['tab']['_type']
	elif is_eface(obj):
	go_type_ptr = obj['_type']
	else:
	return

	ct = gdb.lookup_type("struct runtime.commonType").pointer()
	dynamic_go_type = go_type_ptr['ptr'].cast(ct).dereference()
	return dynamic_go_type['string'].dereference()['str'].string()


	class IfacePrinter:
	"""Pretty print interface values

	Casts the data field to the appropriate dynamic type."""

	def __init__(self, val):
	self.val = val

	def display_hint(self):
	return 'string'

	def to_string(self):
	if self.val['data'] == 0:
	return 0x0
	try:
	dtype = iface_dtype(self.val)
	except:
	return "<bad dynamic type>"

	if not dtype: # trouble looking up, print something reasonable
	return "(%s)%s" % (iface_dtype_name(self.val), self.val['data'])

	try:
	return self.val['data'].cast(dtype).dereference()
	except:
	pass
	return self.val['data'].cast(dtype)


	def ifacematcher(val):
	if is_iface(val) or is_eface(val):
	return IfacePrinter(val)

	goobjfile.pretty_printers.append(ifacematcher)

	#
	# Convenience Functions
	#

	class GoLenFunc(gdb.Function):
	"Length of strings, slices, maps or channels"

	how = ((StringTypePrinter, 'len' ),
	(SliceTypePrinter, 'len'),
	(MapTypePrinter, 'count'),
	(ChanTypePrinter, 'qcount'))

	def __init__(self):
	super(GoLenFunc, self).__init__("len")

	def invoke(self, obj):
	typename = str(obj.type)
	for klass, fld in self.how:
	if klass.pattern.match(typename):
	return obj[fld]

	class GoCapFunc(gdb.Function):
	"Capacity of slices or channels"

	how = ((SliceTypePrinter, 'cap'),
	(ChanTypePrinter, 'dataqsiz'))

	def __init__(self):
	super(GoCapFunc, self).__init__("cap")

	def invoke(self, obj):
	typename = str(obj.type)
	for klass, fld in self.how:
	if klass.pattern.match(typename):
	return obj[fld]

	class DTypeFunc(gdb.Function):
	"""Cast Interface values to their dynamic type.

	For non-interface types this behaves as the identity operation.
	"""

	def __init__(self):
	super(DTypeFunc, self).__init__("dtype")

	def invoke(self, obj):
	try:
	return obj['data'].cast(iface_dtype(obj))
	except:
	pass
	return obj

	#
	# Commands
	#

	sts = ( 'idle', 'runnable', 'running', 'syscall', 'waiting', 'moribund', 'dead', 'recovery')

	def linked_list(ptr, linkfield):
	while ptr:
	yield ptr
	ptr = ptr[linkfield]


	class GoroutinesCmd(gdb.Command):
	"List all goroutines."

	def __init__(self):
	super(GoroutinesCmd, self).__init__("info goroutines", gdb.COMMAND_STACK, gdb.COMPLETE_NONE)

	def invoke(self, arg, from_tty):
	# args = gdb.string_to_argv(arg)
	vp = gdb.lookup_type('void').pointer()
	for ptr in linked_list(gdb.parse_and_eval("'runtime.allg'"), 'alllink'):
	if ptr['status'] == 6: # 'gdead'
	continue
	s = ' '
	if ptr['m']:
	s = '*'
	pc = ptr['sched']['pc'].cast(vp)
	sp = ptr['sched']['sp'].cast(vp)
	blk = gdb.block_for_pc(long((pc)))
	print s, ptr['goid'], "%8s" % sts[long((ptr['status']))], blk.function

	def find_goroutine(goid):
	vp = gdb.lookup_type('void').pointer()
	for ptr in linked_list(gdb.parse_and_eval("'runtime.allg'"), 'alllink'):
	if ptr['status'] == 6: # 'gdead'
	continue
	if ptr['goid'] == goid:
	return [ptr['sched'][x].cast(vp) for x in 'pc', 'sp']
	return None, None


	class GoroutineCmd(gdb.Command):
	"""Execute gdb command in the context of goroutine <goid>.

	Switch PC and SP to the ones in the goroutine's G structure,
	execute an arbitrary gdb command, and restore PC and SP.

	Usage: (gdb) goroutine <goid> <gdbcmd>

	Note that it is ill-defined to modify state in the context of a goroutine.
	Restrict yourself to inspecting values.
	"""

	def __init__(self):
	super(GoroutineCmd, self).__init__("goroutine", gdb.COMMAND_STACK, gdb.COMPLETE_NONE)

	def invoke(self, arg, from_tty):
	goid, cmd = arg.split(None, 1)
	pc, sp = find_goroutine(int(goid))
	if not pc:
	print "No such goroutine: ", goid
	return
	save_frame = gdb.selected_frame()
	gdb.parse_and_eval('$save_pc = $pc')
	gdb.parse_and_eval('$save_sp = $sp')
	gdb.parse_and_eval('$pc = 0x%x' % long(pc))
	gdb.parse_and_eval('$sp = 0x%x' % long(sp))
	try:
	gdb.execute(cmd)
	finally:
	gdb.parse_and_eval('$pc = $save_pc')
	gdb.parse_and_eval('$sp = $save_sp')
	save_frame.select()


	class GoIfaceCmd(gdb.Command):
	"Print Static and dynamic interface types"

	def __init__(self):
	super(GoIfaceCmd, self).__init__("iface", gdb.COMMAND_DATA, gdb.COMPLETE_SYMBOL)

	def invoke(self, arg, from_tty):
	for obj in gdb.string_to_argv(arg):
	try:
	#TODO fix quoting for qualified variable names
	obj = gdb.parse_and_eval("%s" % obj)
	except Exception, e:
	print "Can't parse ", obj, ": ", e
	continue

	dtype = iface_dtype(obj)
	if not dtype:
	print "Not an interface: ", obj.type
	continue

	print "%s: %s" % (obj.type, dtype)

	# TODO: print interface's methods and dynamic type's func pointers thereof.
	#rsc: "to find the number of entries in the itab's Fn field look at itab.inter->numMethods
	#i am sure i have the names wrong but look at the interface type and its method count"
	# so Itype will start with a commontype which has kind = interface

	#
	# Register all convenience functions and CLI commands
	#
	for k in vars().values():
	if hasattr(k, 'invoke'):
	k()