How can I store "image lookup -v address" result inside a variable?

Question

I am able to symbolicate symbol address through following lldb command:

image lookup --address $SYMBOL_ADDRRESS

But while writing a shell script to parse, I am not able to find a way to store the output of above command into a variable or file.

Answer 1

First off, if your script's job is mostly about driving lldb and you happen to know Python, you will be much happier using the lldb module in Python, where you can drive the debugger directly, than getting lldb to produce text output which you parse in the shell script.

The lldb Python module provides API's like SBTarget.ResolveSymbolContextForAddress, which runs the same lookup as image lookup --address but returns the result as a Python lldb.SBSymbolContext object, which you can either query for module/file/line etc using API's on the object. So getting bits of info out of this result will be easier with the lldd API's.

But if you have to use a shell script, then the easiest thing is probably to write the command output to a file and read that back into the shell script. lldb doesn't have generic support for tee-ing command output into a log file yet, but the lldb Python module allows you to run command-line commands and programmatically capture the output.

So you can do it easily from lldb's Python script interpreter:

(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> result = lldb.SBCommandReturnObject()
>>> lldb.debugger.GetCommandInterpreter().HandleCommand("image lookup -va $pc", result)
2
>>> fh = open("/tmp/out.txt", "w")
>>> fh.write(result.GetOutput())
>>> fh.close()
>>> quit
(lldb) plat shell cat /tmp/out.txt
      Address: foo[0x0000000100003f6f] (foo.__TEXT.__text + 15)
      Summary: foo`main + 15 at foo.c:6:3
       Module: file = "/tmp/foo", arch = "x86_64"
  CompileUnit: id = {0x00000000}, file = "/tmp/foo.c", language = "c99"
     Function: id = {0x7fffffff00000032}, name = "main", range = [0x0000000100003f60-0x0000000100003f8a)
     FuncType: id = {0x7fffffff00000032}, byte-size = 0, decl = foo.c:4, compiler_type = "int (void)"
       Blocks: id = {0x7fffffff00000032}, range = [0x100003f60-0x100003f8a)
    LineEntry: [0x0000000100003f6f-0x0000000100003f82): /tmp/foo.c:6:3
       Symbol: id = {0x00000005}, range = [0x0000000100003f60-0x0000000100003f8a), name="main"

You can also write a lldb command in Python that wraps this bit of business, which would make it easier to use. Details on that are here:

https://lldb.llvm.org/use/python-reference.html#create-a-new-lldb-command-using-a-python-function

You could even do a hybrid approach, and make all the lldb work you want to do a custom Python command. That would allow you to use the lldb Python API's to get what info you needed and write it out in whatever format is convenient for you, and would simplify the lldb invocation in your shell script and facilitate recovering the information lldb provided...