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[109.158.45.15]) by smtp.gmail.com with ESMTPSA id c12-20020a05600c0a4c00b00381141f4967sm17454062wmq.35.2022.03.21.07.41.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Mar 2022 07:41:42 -0700 (PDT) From: Andrew Burgess To: Pedro Alves , Tom Tromey , Andrew Burgess via Gdb-patches Subject: Re: [PATCHv2] gdb/x86: handle stap probe arguments in xmm registers In-Reply-To: <705bb6c9-6175-0d6d-7c3a-bcabade3f664@palves.net> References: <20220315105446.3348835-1-aburgess@redhat.com> <20220316141316.465293-1-aburgess@redhat.com> <871qz1ke0r.fsf@tromey.com> <705bb6c9-6175-0d6d-7c3a-bcabade3f664@palves.net> Date: Mon, 21 Mar 2022 14:41:41 +0000 Message-ID: <871qyvtlju.fsf@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.0 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Mar 2022 14:41:47 -0000 Pedro, Tom, Thanks for your feedback on this patch. I've gone ahead and pushed this. For now I don't plan to priorities working on agent expression support for this change, but I'm happy to do so if this becomes important. Thanks, Andrew Pedro Alves writes: > On 2022-03-16 17:23, Tom Tromey wrote: >> Andrew> This is because GDB doesn't currently support placing non-scalar types >> Andrew> on the agent expression evaluation stack. Solving this is clearly >> Andrew> related to the original problem, but feels a bit like a second >> Andrew> problem. I'd like to get feedback on whether my approach to solving >> Andrew> the original problem is acceptable or not before I start looking at >> Andrew> how to handle xmm registers within agent expressions. >> >> Note that there are many things that can't be represented in agent >> expressions. I recall filing a bug report about this -- there are some >> DWARF expressions that can't be translated, and IIRC, floating point >> isn't handled at all. So, I wouldn't worry too much about this. My >> sense is that tracepoints aren't used a whole lot. > > Yeah. They were definitely being used in production a few years back when we were > revamping them, adding support to gdbserver, etc. But it seems like users stopped using > them since. It's possible that the fact that more and more DWARF expressions > can't be converted carries some weight. Or users simply started using other > tools for the job. > > In any case, if I were to tackle the whole problem set today, instead of extending agent > expressions bytecode to be able to do more of what DWARF can do, I'd be looking at expressing > what should be collected via DWARF expressions/locations. I mean, send DWARF expressions > to the target side to be evaluated.