[lldb-dev] Expressions on baremetal target

Tue Mar 31 09:22:04 PDT 2015

A note on this – we’re using this internally for Hexagon, and it works – at least for the fairly simple calls I’ve tried :).

From: lldb-dev-bounces at cs.uiuc.edu [mailto:lldb-dev-bounces at cs.uiuc.edu] On Behalf Of Colin Riley
Sent: Tuesday, March 31, 2015 10:46 AM
To: Sean Callanan
Cc: lldb-dev at cs.uiuc.edu
Subject: Re: [lldb-dev] Expressions on baremetal target

Hey Sean,

Yeah, it's a nice feature - even if it only works with basic types as you noticed. I'll look to fix up the concerns you've identified. We're working on a few other hexagon-related patches to put into review, so I'll add this one to the list. We'll add you as a reviewer when it happens - thanks!

Colin

On 31/03/2015 16:02, Sean Callanan wrote:

Colin,

looking at that patch, it looks like it has some great ideas!

I have a few concerns:

  (a) it looks like it is not 64-bit clean, it assumes that everything it works with is 4 bytes wide;

  (b) it's got some assertions where I'd prefer proper error handling;

  (c) it relies on the PrepareTrivialCall infrastructure which only handles simple argument types; and

  (d) while it tries hard to ensure that strings are exported into the target's memory, it doesn't have any provisions for moving other data that the expression allocated.

While I'd defer to Jim Ingham for comment on the thread plan aspect, I think the interpreter side looks like it has potential.  Also that part might still apply.  I'm fine with ironing out (c) and (d) in tree, working with the LLVM folks to get better solutions, but (a) and (b) and a style nit here and there would currently block integration from my point of view.  Hopefully you agree that those are the easy bits to fix.

If you can resurrect this patch against recent ToT, I'm happy to be a reviewer.

Sean

Sent from my iPad

On Mar 31, 2015, at 4:41 AM, Colin Riley <colin at codeplay.com <mailto:colin at codeplay.com> > wrote:

Hi Bhushan

We ran into this problem whilst doing the Hexagon DSP support in LLDB. 

This review was up (http://reviews.llvm.org/D4672) but is now stale without reviewers. Basically we added the ability to the IR interpreter to call functions on the target using a threadplan which manipulated the stack and registers to call functions and capture any return values, which works well on bare metal without ability to jit.

Maybe the patches can be of help to you. I doubt they would apply cleanly now given the length of time since it was uploaded. It's a valuable feature, but priorities on the list were elsewhere :)

Colin

On 31/03/2015 12:30, Bhushan Attarde wrote:

Hi,

We are debugging a baremetal application using LLDB which is connected to a remote target (supporting GDB remote protocol). 

We are able to execute expressions involving global and frame variables such as:

(lldb) expr var+4

However, LLDB is unable to execute expressions involving function calls.

(lldb) expr (int) bar(1,2)

error: Can't run the expression locally: Interpreter doesn't handle one of the expression's opcodes

Function bar is defined as int bar(int, int).

The expression execution_policy is set to eExecutionPolicyNever as CanJIT() returns false for baremetal applications.

This is because JIT is disabled for static dynamic loader targets.

The IRInterpreter::CanInterpret returns false as it fails to interpret call instruction (call to 'bar' is not an intrinsic).  

Could you please help us on this?

-Regards

Bhushan

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Games Technology Director

Codeplay Software Ltd
45 York Place, Edinburgh, EH1 3HP
Tel: 0131 466 0503
Fax: 0131 557 6600
Website: http://www.codeplay.com
Twitter: https://twitter.com/codeplaysoft

This email and any attachments may contain confidential and /or privileged information and is for use by the addressee only. If you are not the intended recipient, please notify Codeplay Software Ltd immediately and delete the message from your computer. You may not copy or forward it,or use or disclose its contents to any other person. Any views or other information in this message which do not relate to our business are not authorized by Codeplay software Ltd, nor does this message form part of any contract unless so stated.
As internet communications are capable of data corruption Codeplay Software Ltd does not accept any responsibility for any changes made to this message after it was sent. Please note that Codeplay Software Ltd does not accept any liability or responsibility for viruses and it is your responsibility to scan any attachments.
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