Re: Instruction virtual address in TCG Plugins

["Alex Bennée" <alex.bennee@linaro.org>]

Mikhail Tyutin <m.tyutin@yadro.com> writes:

> Greetings,
>
> What is the right way to get virtual address of either translation block or instruction inside of TCG plugin? Does
> plugin API allow that or it needs some extension?
>
> So far I use qemu_plugin_tb_vaddr() inside of my block translation callback to get block virtual address and then
> pass it as 'userdata' argument into qemu_plugin_register_vcpu_tb_exec_cb(). I use it later during code execution.
> It works well for user-mode emulation, but sometimes leads to
> incorrect addresses in system-mode emulation.

You can use qemu_plugin_insn_vaddr and qemu_plugin_insn_haddr. But your
right something under one vaddr and be executed under another with
overlapping mappings. The haddr should be stable though I think.

> I suspect it is because of memory mappings by guest OS that changes virtual addresses for that block.
>
> I also looked at gen_empty_udata_cb() function and considered to extend plugin API to pass a program counter
> value as additional callback argument. I thought it would always give me valid virtual address of an instruction.
> Unfortunately, I didn't find a way to get value of that register in architecture agnostic way (it is 'pc' member in
> CPUArchState structure).

When we merge the register api you should be able to do that. Although
during testing I realised that PC acted funny compared to everything
else because we don't actually update the shadow register every
instruction.

>
> ---
> Mikhail

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro