Skip to content

Commit

Permalink
tools: add debug symbols for node internals
Browse files Browse the repository at this point in the history
Before these changes, only V8 added debug symbols to Node's binary,
limiting the possibilities for debugger's developers to add some
features that rely on investigating Node's internal structures.

These changes are a first steps towards empowering debug tools to
navigate Node's internals strucutres. One example of what can be
achieved with this is shown at nodejs/llnode#122 (a command which prints
information about handles and requests on the queue for a core dump
file). Node debug symbols are prefixed with node_dbg_.

Ref: nodejs/llnode#122
Ref: nodejs/post-mortem#46
  • Loading branch information
Matheus Marchini committed Nov 23, 2017
1 parent 7ab7840 commit 261aa85
Show file tree
Hide file tree
Showing 2 changed files with 224 additions and 1 deletion.
25 changes: 24 additions & 1 deletion node.gyp
Original file line number Diff line number Diff line change
Expand Up @@ -298,6 +298,7 @@
# node.gyp is added to the project by default.
'common.gypi',
'<(SHARED_INTERMEDIATE_DIR)/node_javascript.cc',
'<(SHARED_INTERMEDIATE_DIR)/node-debug-support.cc',
],

'variables': {
Expand Down Expand Up @@ -970,7 +971,29 @@
}]]
}],
]
}
},
{
'target_name': 'node_postmortem_metadata',
'type': 'none',
'toolsets': ['host'],
'actions': [
{
'action_name': 'gen-postmortem-metadata',
'process_outputs_as_sources': 1,
'inputs': [
'./tools/gen-postmortem-metadata.py',
],
'outputs': [
'<(SHARED_INTERMEDIATE_DIR)/node-debug-support.cc',
],
'action': [
'python',
'./tools/gen-postmortem-metadata.py',
'<@(_outputs)',
]
}
]
},
], # end targets

'conditions': [
Expand Down
200 changes: 200 additions & 0 deletions tools/gen-postmortem-metadata.py
Original file line number Diff line number Diff line change
@@ -0,0 +1,200 @@
#!/usr/bin/env python

#
# gen-postmortem-metadata.py output_file.cc
#
# Creates debugging symbols to help naviage Node's internals using post-mortem
# debugging tools.
#

import os
import fnmatch
import re
from glob import glob
import sys


class DebugSymbol(object):
type_ = 'int'
_prefix = 'nodedbg_'

def __init__(self, name, value, headers=[], type_=None):
self.name = name
self.value = value
self.headers = headers
self.type_ = type_ or DebugSymbol.type_

@classmethod
def get_headers(cls, debug_symbols):
'''
Return a list of headers without duplicates, preserving the order they were
declared
'''
seen = set()
headers = [debug_symbol.headers for debug_symbol in debug_symbols]
headers = sum(headers, [])

result = []
for h in headers:
if not h in seen:
seen.add(h)
result.append(h)

return result

@property
def declare(self):
return '{type} {prefix}{name};'.format(
type=self.type_,
prefix=self._prefix,
name=self.name,
)

@property
def fill(self):
return '{prefix}{name} = {value};'.format(
prefix=self._prefix,
name=self.name,
value=self.value,
)


debug_symbols = [
DebugSymbol(
name='environment_context_idx_embedder_data',
value='Environment::kContextEmbedderDataIndex',
headers=['env.h'],
type_='int',
),
DebugSymbol(
name='class__BaseObject__persistent_handle',
value='nonstandard_offsetof(BaseObject, persistent_handle_)',
headers=['base_object-inl.h'],
type_='size_t',
),
DebugSymbol(
name='class__Environment__handleWrapQueue',
value='nonstandard_offsetof(Environment, handle_wrap_queue_)',
headers=['env.h'],
type_='size_t',
),
DebugSymbol(
name='class__HandleWrap__node',
value='nonstandard_offsetof(HandleWrap, handle_wrap_queue_)',
headers=['handle_wrap.h'],
type_='size_t',
),
DebugSymbol(
name='class__HandleWrapQueue__headOffset',
value='offsetof(Environment::HandleWrapQueue, head_)',
headers=['env.h'],
type_='size_t',
),
DebugSymbol(
name='class__HandleWrapQueue__nextOffset',
value='offsetof(ListNode<HandleWrap>, next_)',
headers=['handle_wrap.h', 'util.h'],
type_='size_t',
),
DebugSymbol(
name='class__Environment__reqWrapQueue',
value='nonstandard_offsetof(Environment, req_wrap_queue_)',
headers=['env.h'],
type_='size_t',
),
DebugSymbol(
name='class__ReqWrap__node',
value='nonstandard_offsetof(ReqWrap<uv_req_t>, req_wrap_queue_)',
headers=['req_wrap.h'],
type_='size_t',
),
DebugSymbol(
name='class__ReqWrapQueue__headOffset',
value='offsetof(Environment::ReqWrapQueue, head_)',
headers=['env.h'],
type_='size_t',
),
DebugSymbol(
name='class__ReqWrapQueue__nextOffset',
value='offsetof(ListNode<ReqWrap<uv_req_t>>, next_)',
headers=['req_wrap.h', 'util.h'],
type_='size_t',
),
]


template = '''
/*
* This file is generated by {filename}. Do not edit directly.
*/
// Need to import standard headers before redefining private, otherwise it
// won't compile
{standard_includes}
int GenDebugSymbol();
#define private friend int GenDebugSymbol(); private
#define nonstandard_offsetof(CLASS, FIELD) reinterpret_cast<uintptr_t>\
(&(static_cast<CLASS*>(0)->FIELD))
{includes}
{declare_symbols}
namespace node {{
int GenDebugSymbol() {{
{fill_symbols}
return 1;
}}
int debug_symbols_generated = GenDebugSymbol();
}}
'''


def get_standard_includes():
'''
Try to find all standard C++ headers needed by node and its dependencies
'''
includes = ["algorithm", "array", "atomic", "bitset", "cctype", "climits",
"cmath", "cstdarg", "cstddef", "cstdint", "cstdio", "cstdlib", "cstring",
"ctime", "deque", "exception", "forward_list", "fstream", "functional",
"iomanip", "iosfwd", "iostream", "istream", "iterator", "limits", "list",
"map", "memory", "new", "ostream", "queue", "set", "sstream", "stack",
"streambuf", "string", "tuple", "type_traits", "typeinfo", "unordered_map",
"unordered_set", "utility", "vector"]
return includes


def create_symbols_file():
out = file(sys.argv[1], 'w')
headers = DebugSymbol.get_headers(debug_symbols)
includes = ['#include "{0}"'.format(header) for header in headers]
includes = '\n'.join(includes)

standard_includes = get_standard_includes()
standard_includes = ['#include <{0}>'.format(include) for include in standard_includes]
standard_includes = '\n'.join(standard_includes)

declare_symbols = '\n'.join([symbol.declare for symbol in debug_symbols])
fill_symbols = '\n'.join([symbol.fill for symbol in debug_symbols])

out.write(template.format(
filename=sys.argv[0],
includes=includes,
standard_includes=standard_includes,
declare_symbols=declare_symbols,
fill_symbols=fill_symbols,
))


if len(sys.argv) < 2:
print('usage: {0} output.cc'.format(sys.argv[0]))
sys.exit(2)


create_symbols_file()

0 comments on commit 261aa85

Please sign in to comment.