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Re: Function arguments question on ARM (RaspPi)
- From: Josh Stone <jistone at redhat dot com>
- To: Thomas Winkler <tom dot winkler at gmail dot com>
- Cc: "Frank Ch. Eigler" <fche at redhat dot com>, systemtap at sourceware dot org
- Date: Mon, 21 Dec 2015 12:16:57 -0800
- Subject: Re: Function arguments question on ARM (RaspPi)
- Authentication-results: sourceware.org; auth=none
- References: <CA+y5ay7Jbg6PfaEGQd6tRXNoK9ZL6Gi6SaUU9WNu1OPoDewZ4Q at mail dot gmail dot com> <y0mpoxzsuex dot fsf at fche dot csb>
On 12/21/2015 07:17 AM, Frank Ch. Eigler wrote:
> Yeah, assumig you're right about the _arg* ones being correct, this
> should not be happening. $$parms works based on dwarf debuginfo;
> _arg* works on hard-coded-in-tapset abi assumptions. They should
> normally match.
One consequence of that abi assumption is that the *_arg functions only
work in a proper function entry point. If the function you're probing
has been inlined, then only debuginfo can possibly know the right way to
fetch those parameters. You can make sure it's not an inlined probe
like: module("...").function("...").call
But since you think the $$parms values are the incorrect ones, that
suggests perhaps the compiler is giving bad debuginfo.