Re: [Qemu-devel] Doubts about qemu tcg/tci

[陳韋任 <chenwj@iis.sinica.edu.tw>]

> I'm trying to read the asm code generated with the -D qemu option, but I am
> having some difficulties.

  Should be "-d" option.
 
> First, I've seen that the generated asm is allocated in different address
> ranges. The beginning of the dump says:
> 
> end_code    0x080486dc
> start_code  0x08048000

  This is guest binary range.
 
> but the first instruction's address is: 0x6022caf0

  This is the address of host binary in the code cache.
 
> Am I misunderstanding something? How exactly this reallocation happens (or
> where in the source code am I able to track and understand the process)?

  http://lugatgt.org/content/qemu_internals/downloads/slides.pdf
  http://m1.archiveorange.com/m/att/1XS1v/ArchiveOrange_YD2LcLkRqU2so0i2Zoj99h2bwUsa.pdf

  Should be good start.
 
> Second, what exactly means the identifying letters of arguments counted in
> front of each instruction (i, o, c) ? Is it too hard to create a patch on
> the disassembly function to also output its values?

  Sorry, I don't understand what you're trying to do. Where do you see those
identifying letters?
 
> Third, Is there a trivial way for me to track an original function inside
> the generated asm dump? I mean, if I create a C function called foo(), that
> is called somewhere inside the main function, what should I do in order to
> find the translated instructions inside the outputted dump?

  `objdump -D` should show you the address of the function you're interested in.
For example, function foo() locates 0x080483b4. You can lookup qemu.log for that
address. Also, it seems QEMU will log the function name, too. Say,

----------------
IN: foo          <---
0x080483b4:  push   %ebp
0x080483b5:  mov    %esp,%ebp
0x080483b7:  pop    %ebp
0x080483b8:  ret
 
 
> Finally, I've been trying to find material about how this translation works
> properly, but I've been unable to find much. Is there something I should be
> reading before asking around here? If yes, please, point me to it!

  See above.

Regards,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj