Re: [Qemu-devel] classic emulator Vs QEMU-TCG

[Stefano Bonifazi <stefboombastic@gmail.com>]

On 12/16/2010 04:41 PM, Peter Maydell wrote:
> Some hints:
>   * go and look up the C syntax for function pointers and
> casting things to function pointers
Yup! See the reply to Mr. Santosa, thank you!
>   * code_gen_prologue[] contains code which has been generated
> once on startup -- go and find the function which is doing this,
> which ought to tell you what the prologue code actually does...
Is that the following?
> /* init global prologue and epilogue */
>     s->code_buf = code_gen_prologue;
>     s->code_ptr = s->code_buf;
>     tcg_target_qemu_prologue(s);


Trying to understand the pseudo-assembly in tcg_target_qemu_prologue (in 
file tcg-target.c), I think it builds an assembly function scheleton 
storying it inside code_gen_prologue array..
Cosidering the implementation of that function for i386 I think the jmp 
*%eax is the actual code that jumps to the host binary produced by TCG 
from the target binary.. in fact, if I am not wrong,this binary function 
is what is actually called by tcg_qemu_tb_exec(tb_ptr) macro with tb_ptr 
passed to the function in %eax, thus "jmp *%eax" starts the execution of 
the binary code .. am I wrong?

>   * try single stepping individual machine instructions in the
> debugger as you go through tcg_qemu_tb_exec() and matching
> this up with what is really happening here and with the bits of
> qemu which generated that code.
>
> -- PMM
I would have already done that.. unluckily I have always used IDE with 
integrated debuggers, and I can't find an IDE for loading this project.. 
I guess I have no other choice than learning also gdb
Thank you for your tips! :)
Best Regards!
Stefano B.