RE: A little help with JIT support

[Rouslan Korneychuk <rouslank@msn.com>]

On Wed, 01 May 2013 16:34:26 +0200, Jan Kratochvil wrote:
> On Wed, 01 May 2013 01:05:01 +0200, Rouslan Korneychuk wrote:
> > Are the addresses in an in-memory object file supposed to be absolute addresses?
>
> According to GDB's jit.c jit_bfd_try_read_symtab yes:
>
> /* Read the section address information out of the symbol file. Since the
> file is generated by the JIT at runtime, it should all of the absolute
> addresses that we care about. */
> +
> /* We assume that these virtual addresses are absolute, and do not
> treat them as offsets. */
> sai->other[i].addr = bfd_get_section_vma (nbfd, sec);
>
> When you generate it at runtime it should not matter much IMO, instead of
> relocating it in GDB you can already relocate it yourself while generating the
> symbol file at runtime.

Ah, thank you. 		 	   		  
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Date: Thu, 02 May 2013 02:19:00 -0000
From: Suchakrapani Datt Sharma <suchakrapani.sharma@polymtl.ca>
To: lgustavo@codesourcery.com
Cc: gdb@sourceware.org
Subject: Re: GDB fast tracepoint query
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Hi,

> AFAIU, the fast tracepoint jump pad will always be there if a trace
> experiment is running (with at least one active fast tracepoint set),
> which means GDB will take the path through the fast tracepoint's jump
> pad, save whatever needs to be saved, execute actions and then exit
> through the jump pad again. So there should be some small overhead there
> even if no actions are actually executed.
>
> As for the time when the instruction is modified, it is during the trace
> experiment startup, during "tstart". "ftrace" or "trace" will just
> register the tracepoint internally inside gdb.
>
> Luis

Thanks a lot for the info :) Sorry for the late reply

Suchakra

--
Suchakrapani Datt Sharma
Laboratorie DORSAL
École Polytechnique de Montréal