tools: add script with commands to facilitate dev

Some tasks are very common when working on llnode, especially when upgrading a V8 version. This new script is intended to make developers life easier by simplifying tasks which usually require printfs on llnode code or manually inspecting the memory of a process. Hopefully we'll add more commands in the future. PR-URL: Newspaper Article Byline

Author: Delete Instagram Account

tools/helpers.py

@@ -0,0 +1,96 @@
+""" Helper commands to make development of llnode easier. No API stability
+guarantees for these commands (at least for now).
+
+To use it, run:
+
+ (llnode) command script import ./tools/helpers.py
+
+Or start llnode with:
+
+ $ llnode -o 'command script import ./tools/helpers.py'
+"""
+import struct
+
+import lldb
+
+
+def int_from_bytearray(uint, size, target):
+ byte_order = target.GetByteOrder()
+
+ fmt = ""
+
+ # https://docs.python.org/3.2/library/struct.html#byte-order-size-and-alignment
+ # < is little endian, > is big endian
+ if byte_order == lldb.eByteOrderLittle:
+ fmt += "<"
+ elif byte_order == lldb.eByteOrderBig:
+ fmt += ">"
+ else:
+ raise ValueError("Unexpected byte order %d" % byte_order)
+
+ # https://docs.python.org/3.2/library/struct.html#format-characters
+ if size == 1:
+ fmt += "B"
+ elif size == 2:
+ fmt += "H"
+ elif size == 4:
+ fmt += "I"
+ elif size == 8:
+ fmt += "Q"
+ else:
+ raise ValueError("Unexpected size %d" % size)
+ return struct.unpack(fmt, uint)[0]
+
+
+def brute(debugger, command, result, internal_dict):
+ """ v8-brute <addr>
+ This command will try to run `v8 inspect` on 20 object-aligned addresses
+ following <addr>. Useful to find all objects on the stack, or all objects
+ after a given object field, etc.
+ """
+ process = debugger.GetSelectedTarget().GetProcess()
+ if not command:
+ return
+
+ for i in range(20):
+ addr = int(command, 16) + (8 * i)
+ error = lldb.SBError()
+ obj = process.ReadUnsignedFromMemory(addr, 8, error)
+ if error.Fail():
+ print("failed for 0x%x" % addr)
+ continue
+ print("v8 inspect 0x%lx" % obj)
+ debugger.HandleCommand("v8 inspect 0x%lx" % obj)
+
+
+def get_constants(debugger, command, result, internal_dict):
+ """ v8-get-constants [pattern]
+ This command will return all constants prefixed by v8dbg and nodedbg, with
+ respective values for each constant. Useful when looking at missing types,
+ offsets, etc. Optional pattern parameter will filter symbol names before
+ showing them (for example, running `v8-get-constants v8dbg_type_` will
+ return all type constants).
+ """
+ target = debugger.GetSelectedTarget()
+
+ for module in target.module_iter():
+ for symbol in module:
+ name = symbol.GetName()
+ if name is None:
+ continue
+ if name.startswith("v8dbg_") or name.startswith("nodedbg_"):
+ if command and command not in name:
+ continue
+ start = symbol.GetStartAddress()
+ size = symbol.GetEndAddress().GetOffset() - start.GetOffset()
+
+ error = lldb.SBError()
+ uint = bytes(target.ReadMemory(start, size, error))
+ if error.Success():
+ uint = int_from_bytearray(uint, size, target)
+ print("%s: %d" % (name, uint))
+ else:
+ print('error: ', error.GetCString())
+
+lldb.debugger.HandleCommand('command script add -f helpers.brute v8-brute-inspect')
+lldb.debugger.HandleCommand('command script add -f helpers.get_constants v8-get-constants')