[68]l and runtime: GDB support for interfaces and goroutines.
R=rsc
CC=golang-dev
https://golang.org/cl/3477041
diff --git a/src/pkg/runtime/runtime-gdb.py b/src/pkg/runtime/runtime-gdb.py
index 422809e..a7ca94c 100644
--- a/src/pkg/runtime/runtime-gdb.py
+++ b/src/pkg/runtime/runtime-gdb.py
@@ -9,10 +9,20 @@
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
#
@@ -95,7 +105,7 @@
class ChanTypePrinter:
"""Pretty print chan[T] types.
- Map-typed go variables are really pointers. dereference them in gdb
+ Chan-typed go variables are really pointers. dereference them in gdb
to inspect their contents with this pretty printer.
"""
@@ -117,18 +127,109 @@
ptr = ptr['link']
#
-# Register all the *Printer classes
+# 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
+ if klass.pattern.match(str(val.type)):
+ return klass(val)
+ except:
+ pass
return matcher
-gdb.current_objfile().pretty_printers.extend([makematcher(k) for k in vars().values() if hasattr(k, 'pattern')])
+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) == "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."
+
+ 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['data'].cast(ct).dereference()
+ dtype_name = dynamic_go_type['string'].dereference()['str'].string()
+ type_size = int(dynamic_go_type['size'])
+ uintptr_size = int(dynamic_go_type['size'].type.sizeof) # size is itself an uintptr
+ dynamic_gdb_type = lookup_type(dtype_name)
+ if type_size > uintptr_size:
+ dynamic_gdb_type = dynamic_gdb_type.pointer()
+ return dynamic_gdb_type
+
+
+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):
+ try:
+ dtype = iface_dtype(self.val)
+ except:
+ return "<bad dynamic type>"
+ 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
@@ -137,35 +238,158 @@
class GoLenFunc(gdb.Function):
"Length of strings, slices, maps or channels"
- how = ((StringTypePrinter, 'len' ),
- (SliceTypePrinter, 'len'),
- (MapTypePrinter, 'count'),
- (ChanTypePrinter, 'qcount'))
+ 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:
+ 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'))
+ 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:
+ 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
+ m = ptr['m']
+ s = ' '
+ if m:
+ pc = m['sched']['pc'].cast(vp)
+ sp = m['sched']['sp'].cast(vp)
+ s = '*'
+ else:
+ 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['m'] or 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 convience functions and CLI commands
#
