[lldb-dev] [RFC] lldb integration with (user mode) qemu

[Pavel Labath via lldb-dev]

On 04/11/2021 22:46, Jessica Clarke via lldb-dev wrote:
> On Fri, Oct 29, 2021 at 05:55:02AM +0000, David Spickett via lldb-dev wrote:
>>> I don't think it does. Or at least I'm not sure how do you propose to solve them (who is "you" in the paragraph above?).
>>
>> I tend to use "you" meaning "you or I" in hypotheticals. Same thing as
>> "if I had" but for whatever reason I phrase it like that to include
>> the other person, and it does have its ambiguities.
>>
>> What I was proposing is, if I was correct (which I wasn't) then having
>> the user "platform select qemu-user" would solve things. (which it
>> doesn't)
>>
>>> What currently happens is that when you open a non-native (say, linux) executable, the appropriate remote platform gets selected automatically.
>>
>> ...because of this. I see where the blocker is now. I thought remote
>> platforms had to be selected before they could claim.
>>
>>> If we do have a prompt, then this may not be so critical, though I expect that most users would still prefer it we automatically selected qemu.
>>
>> Seems reasonable to put qemu-user above remote-linux. Only claiming if
>> qemu-user has been configured sufficiently. I guess architecture would
>> be the minimum setting, given we can't find the qemu binary without
>> it.
>>
>> Is this similar in any way to how the different OS remote platforms
>> work? For example there is a remote-linux and a remote-netbsd, is
>> there enough information in the program file itself to pick just one
>> or is there an implicit default there too?
>> (I see that platform CreateInstance gets an ArchSpec but having
>> trouble finding where that comes from)
> 
> Please make sure you don't forget that bsd-user also exists (and after
> living in a fork for many years for various boring reasons is in the
> middle of being upstreamed), so don't tie it entirely to remote-linux.
> 

I am. In fact one of the reason's I haven't started putting up patches 
yet is because I'm trying to figure out the best way to handle this. :)

My understanding is (let me know if I'm wrong) is that user-mode qemu 
can emulate a different arhitecture, but not a different os. So, the 
idea is that the "qemu" platform would forward all operations that don't 
need special handling to the "host" platform. That would mean you get 
freebsd behavior when running on freebsd, etc.

pl