[Qemu-devel] Re: x86_64 debugging while in 32-bit mode

[vagran <vagran.ast@gmail.com>]

> Hi,
> I have a problem with debugging 64-bit emulation using Qemu GDB stub. The
> problem is that Qemu always sends x86_64 registers set disregarding 
> current
> actual mode of an emulated CPU. It results in error message in GDB - 
> "Remote 'g'
> packet reply is too long: ...". Yes, I understand that in case I will 
> execute
> "set architecture i386:x86-64:intel" command it will show me correct 
> registers
> content. But the problem is that in such case it will incorrectly try to
> disassemble the code and unwind the stack - it will interpret it as 
> 64-bit while
> it is actually 32-bit. In my understanding Qemu should dynamically 
> change the
> format of "g" and "G" packets depending on current CPU mode. On the 
> other end,
> user could change manually GDB current architecture by corresponding "set
> architecture" command.
> Please correct me, if I am not right. May be there is some existing 
> methodology
> of debugging Qemu emulated x86_64 architecture in different CPU modes. 
> For now,
> I have strong intention to make a patch for Qemu GDB stub, at least 
> for me. But
> I have impression that this should be corrected in official release too.
Hi,
Seems the problem is not present on the latest version of the Qemu. I 
had several
installed and occasionally launched old one. Sorry for inconvenience.

Best regards,
Artyom.