Jump visualization feature for objdump.

[Fangrui Song]

On 2019-11-06, Thomas Troeger wrote:
>Dear all,
>
>I have written a program that adds visualization of jumps inside a function to the output of objdump in the form of a post-processor
>
>$ objdump -wzSCD binary | postprocessor
>
>Is that feature interesting enough to include it into objdump, for example behind a command-line switch like `--visualize-jumps'? If yes, what is the workflow to add this feature? I could of course port it from my tool, which is written in C++14, but there is the question who will review a patch for inclusion when I have it finished, and what are other prerequisites (source code formatting, test cases ...)?
>
>Please enlighten me with your answers.
>
>Regards,
>Thomas.
>
>P.S.: Example output from a running `/bin/bash' process (the program does other stuff besides the visualization):
>
>000055edb4520380 <unset_bash_input@@Base>:
>    55edb4520380:	          8b 05 9a 53 0e 00    	mov    0xe539a(%rip),%eax        # 115720 <default_buffered_input@@Base> -> 55edb451d03d
>    55edb4520386:	          85 ff                	test   %edi,%edi
>    55edb4520388:	/-------- 75 3e                	jne    303c8 <unset_bash_input@@Base+0x48> -> 55edb45203c8
>    55edb452038a:	|         85 c0                	test   %eax,%eax
>    55edb452038c:	|     /-- 7e 32                	jle    303c0 <unset_bash_input@@Base+0x40> -> 55edb45203c0
>    55edb452038e:	|  /--|-> 48 83 ec 08          	sub    $0x8,%rsp
>    55edb4520392:	|  |  |   89 c7                	mov    %eax,%edi
>    55edb4520394:	|  |  |   e8 f7 47 04 00       	callq  74b90 <close_buffered_fd@@Base> -> 55edb4564b90
>    55edb4520399:	|  |  |   c7 05 ad 25 0f 00 ff ff ff ff 	movl   $0xffffffff,0xf25ad(%rip)        # 122950 <bash_input@@Base+0x10> -> 55edb45ca79d
>    55edb45203a3:	|  |  |   c7 05 73 53 0e 00 ff ff ff ff 	movl   $0xffffffff,0xe5373(%rip)        # 115720 <default_buffered_input@@Base> -> 55edb451d03d
>    55edb45203ad:	|  |  |   c7 05 89 25 0f 00 00 00 00 00 	movl   $0x0,0xf2589(%rip)        # 122940 <bash_input@@Base> -> 55edb45ca78d
>    55edb45203b7:	|  |  |   48 83 c4 08          	add    $0x8,%rsp
>    55edb45203bb:	|  |  |   c3                   	retq
>    55edb45203bc:	|  |  |   0f 1f 40 00          	nopl   0x0(%rax)
>    55edb45203c0:	|  |  \-> c3                   	retq
>    55edb45203c1:	|  |      0f 1f 80 00 00 00 00 	nopl   0x0(%rax)
>    55edb45203c8:	\--|----> 85 c0                	test   %eax,%eax
>    55edb45203ca:	   \----- 79 c2                	jns    3038e <unset_bash_input@@Base+0xe> -> 55edb452038e
>    55edb45203cc:	          c3                   	retq
>    55edb45203cd:	          0f 1f 00             	nopl   (%rax)
>
>[...]
>
>000055edb45218a0 <with_input_from_stdin@@Base>:
>    55edb45218a0:	                   83 3d 99 10 0f 00 01 	cmpl   $0x1,0xf1099(%rip)        # 122940 <bash_input@@Base> -> 55edb45ca78d
>    55edb45218a7:	/----------------- 74 4f                	je     318f8 <with_input_from_stdin@@Base+0x58> -> 55edb45218f8
>    55edb45218a9:	|                  48 8b 05 d8 c5 0e 00 	mov    0xec5d8(%rip),%rax        # 11de88 <stream_list@@Base> -> 55edb451d017
>    55edb45218b0:	|                  48 85 c0             	test   %rax,%rax
>    55edb45218b3:	|        /-------- 74 19                	je     318ce <with_input_from_stdin@@Base+0x2e> -> 55edb45218ce
>    55edb45218b5:	|        |         83 78 08 01          	cmpl   $0x1,0x8(%rax)
>    55edb45218b9:	|        |  /----- 75 0b                	jne    318c6 <with_input_from_stdin@@Base+0x26> -> 55edb45218c6
>    55edb45218bb:	|  /-----|--|----- eb 3c                	jmp    318f9 <with_input_from_stdin@@Base+0x59> -> 55edb45218f9
>    55edb45218bd:	|  |     |  |      0f 1f 00             	nopl   (%rax)
>    55edb45218c0:	|  |     |  |  /-> 83 78 08 01          	cmpl   $0x1,0x8(%rax)
>    55edb45218c4:	|  |  /--|--|--|-- 74 32                	je     318f8 <with_input_from_stdin@@Base+0x58> -> 55edb45218f8
>    55edb45218c6:	|  |  |  |  \--|-> 48 8b 00             	mov    (%rax),%rax
>    55edb45218c9:	|  |  |  |     |   48 85 c0             	test   %rax,%rax
>    55edb45218cc:	|  |  |  |     \-- 75 f2                	jne    318c0 <with_input_from_stdin@@Base+0x20> -> 55edb45218c0
>    55edb45218ce:	|  |  |  \-------> 4c 8b 05 cb c5 0e 00 	mov    0xec5cb(%rip),%r8        # 11dea0 <current_readline_line@@Base> -> 55edb451d017
>    55edb45218d5:	|  |  |            48 8d 0d 85 9d 0a 00 	lea    0xa9d85(%rip),%rcx        # db661 <_IO_stdin_used@@Base+0x661>
>    55edb45218dc:	|  |  |            ba 01 00 00 00       	mov    $0x1,%edx
>    55edb45218e1:	|  |  |            48 8d 35 a8 f1 ff ff 	lea    -0xe58(%rip),%rsi        # 30a90 <pretty_print_loop@@Base+0xd0> -> 55edb4520a90
>    55edb45218e8:	|  |  |            48 8d 3d 51 f4 ff ff 	lea    -0xbaf(%rip),%rdi        # 30d40 <pretty_print_loop@@Base+0x380> -> 55edb4520d40
>    55edb45218ef:	|  |  |            e9 0c ff ff ff       	jmpq   31800 <init_yy_io@@Base> -> 55edb4521800
>    55edb45218f4:	|  |  |            0f 1f 40 00          	nopl   0x0(%rax)
>    55edb45218f8:	\--|--\----------> c3                   	retq
>    55edb45218f9:	   \-------------> c3                   	retq
>    55edb45218fa:	                   66 0f 1f 44 00 00    	nopw   0x0(%rax,%rax,1)

radare2[1] can draw such edges and even control flow graphs[2] in the terminal.
I wonder what people think of doing more "UI" work in the standard
disassembly utility, objdump.

(radare2 uses capstone as its default disassembler backend.  capstone was
 created from rewriting part of 2014 llvm MC C++ code in C. IIRC it is
 more difficult to upgrade to a newer llvm, than rewriting it.)

[1]: https://rada.re/n/
[2]: https://monosource.gitbooks.io/radare2-explorations/content/intro/visual_graphs.html