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([2804:7f0:b403:42c7:7a6a:84e4:83a0:56d7]) by smtp.gmail.com with ESMTPSA id t32-20020a056a0013a000b006ed53b2652fsm2916102pfg.101.2024.04.09.06.23.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Apr 2024 06:23:14 -0700 (PDT) Subject: Re: [PATCH v3 7/7] gdb: Document qMemTagCheckAddr packet To: Tom Tromey Cc: gdb-patches@sourceware.org, luis.machado@arm.com, thiago.bauermann@linaro.org References: <20240404064819.2848899-1-gustavo.romero@linaro.org> <20240404064819.2848899-8-gustavo.romero@linaro.org> <87msq363yk.fsf@tromey.com> From: Gustavo Romero Message-ID: <44bc1d7f-65da-3db2-d3dd-a6b27beb2e9c@linaro.org> Date: Tue, 9 Apr 2024 10:23:11 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <87msq363yk.fsf@tromey.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-6.2 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Hi Tom, On 4/8/24 4:37 PM, Tom Tromey wrote: >>>>>> "Gustavo" == Gustavo Romero writes: > > Gustavo> +@item @w{} > Gustavo> +An empty reply indicates that @samp{qMemTagCheckAddr} is not supported by the > Gustavo> +stub. This situation should not occur because @value{GDBN} will only send this > Gustavo> +packet if the stub has advertised support for memory tagging check via the > Gustavo> +@samp{memory-tagging-check-addr} feature in @samp{qSupported}. > > Is querying really needed in this case? > Like, if there is some user feature that requires knowing whether this > work before ever trying it, then I guess that would be a good > justification. In other cases, it seems to me that simply trying to use > a packet is better than a qSupported response; or at least I don't know > why it wouldn't be. That's right, I think we are in sync here. Luis communicated to me last week (private conversation) about this possibility, hence for v4 we just try to send the qMemTagCheckAddr packet, and if it fails (empty reply) there is a fallback to the current code path, which reads the smaps. So I'm dropping the memory-tagging-check-addr feature. Thanks for review! Cheers, Gustavo