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Date: Sat, 16 Nov 2024 17:11:58 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Alan Maguire <alan.maguire@oracle.com>
Cc: yonghong.song@linux.dev, dwarves@vger.kernel.org, ast@kernel.org,
	andrii@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net,
	kernel-team@fb.com, song@kernel.org, eddyz87@gmail.com,
	olsajiri@gmail.com
Subject: Re: [PATCH v3 dwarves 0/2] Check DW_OP_[GNU_]entry_value for
 possible parameter matching
Message-ID: <Zzj8jl4TKSEDnPrL@x1>
References: <20241115113605.1504796-1-alan.maguire@oracle.com>
 <a1ffc678-5d72-45f5-a304-07be3cca7f86@oracle.com>
 <Zzdupj2ifjERTijl@x1>
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In-Reply-To: <Zzdupj2ifjERTijl@x1>

On Fri, Nov 15, 2024 at 12:54:17PM -0300, Arnaldo Carvalho de Melo wrote:
> On Fri, Nov 15, 2024 at 11:40:16AM +0000, Alan Maguire wrote:
> > On 15/11/2024 11:36, Alan Maguire wrote:
> > > Currently, pahole relies on DWARF to find whether a particular func
> > > has its parameter mismatched with standard or optimized away.
> > > In both these cases, the func will not be put in BTF and this
> > > will prevent fentry/fexit tracing for these functions.
> > > 
> > > The current parameter checking focuses on the first location/expression
> > > to match intended parameter register. But in some cases, the first
> > > location/expression does not have expected matching information,
> > > but further location like DW_OP_[GNU_]entry_value can provide
> > > information which matches the expected parameter register.
> > > 
> > > Patch 1 supports this; patch 2 adds locking around dwarf_getlocation*
> > > as it is unsafe in a multithreaded environment.
> > >
> > 
> > apologies, forgot to note
> > 
> > Changes since v2:
> > 
> > - handle multiple DW_OP_entry_value expressions by bailing if the
> > register matches expected, otherwise save reg in return value (Eduard
> > Yonghong, Jiri, patch 1)
> 
> Thanks, applied locally, will perform tests and push publicly later
> today.

Did the tests/tests run, passes, pushed out to the master branch.

Thanks!

- Arnaldo