From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca by simark.ca with LMTP id K03JLWugs18SfQAAWB0awg (envelope-from ) for ; Tue, 17 Nov 2020 05:05:31 -0500 Received: by simark.ca (Postfix, from userid 112) id AE06B1F08B; Tue, 17 Nov 2020 05:05:31 -0500 (EST) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on simark.ca X-Spam-Level: X-Spam-Status: No, score=-1.1 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server2.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPS id 50FC41E58D for ; Tue, 17 Nov 2020 05:05:30 -0500 (EST) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id A1C6F3858019; Tue, 17 Nov 2020 10:05:29 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A1C6F3858019 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1605607529; bh=SOW52mcW9VVxN/a1PDIBADsKHJKnaJxCNts4eLLZjJo=; h=References:In-Reply-To:Date:Subject:To:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=l71WONUjL86ToOkn+wtrCaHV91lbYV9/l9jCfcKLC8qGKCBHa2JxR9SdXqBfu4T43 ORrzkrswC64AU4K2/MUoNHbzh2nRU2d4mxe4TpUtnbS395OvC0Di/cp/p3jWz1xujl q4gfJSHikSyHb9uJJ2t3Owj74I7qcjNYURGaxc3I= Received: from mail-vk1-xa43.google.com (mail-vk1-xa43.google.com [IPv6:2607:f8b0:4864:20::a43]) by sourceware.org (Postfix) with ESMTPS id 645F03858013 for ; Tue, 17 Nov 2020 10:05:26 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 645F03858013 Received: by mail-vk1-xa43.google.com with SMTP id w123so4404678vka.4 for ; Tue, 17 Nov 2020 02:05:26 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=SOW52mcW9VVxN/a1PDIBADsKHJKnaJxCNts4eLLZjJo=; b=W8Ee41eFQq2vYOeLB8/77rhHAbO9MG2Sm1+VNJdoWQkmtok7pzkai8GpTLEb7jMb/h V1ChiMYpzD1H7BMowgCnJ2CHtUB/YPA6niGSlrsJbRQQJu3VF3vKeOBtFMvhOWmtidIk q8h11YBrZXkbYzllP7HxDo2A8jsBjbcgAGsGOI9+uUf768ylZXDCRaTs0uEWh8DDNaQV kOYJbo98LPWDUXIlVJ/kFpVTIRGM5W5aaYr7/tuPmnWoX5YeRk6j0lHLdtmcij5rfl0/ 2AQG/Wjs/21fYcJ5YPlKg9GfoqWiFckFqACblRPeiFDMKCMq8TufQz+9YTOhP+xsttsp Is7g== X-Gm-Message-State: AOAM530CTq8zfez5Nsf/lcQCbam7r+FhRcAi/Ff5HLmBmckUgjGlutxH B62xVqgZphCPJ3djSZCT6nWRy+o5rp1iVeYHAVsm3Q== X-Google-Smtp-Source: ABdhPJz4tAQid5OOl0YS716JzihD8DvwM8Or6bc80StYci4TZaV6Jov5KGPhH+jfp2cMVluX5y0ORds8zhaAHa7jupk= X-Received: by 2002:a1f:a4cf:: with SMTP id n198mr10388323vke.0.1605607525989; Tue, 17 Nov 2020 02:05:25 -0800 (PST) MIME-Version: 1.0 References: <20201109170435.15766-1-luis.machado@linaro.org> <20201109170435.15766-8-luis.machado@linaro.org> <83ft5i4fwl.fsf@gnu.org> <08cb075e-018c-474e-abd4-b76ba1ed6a52@linaro.org> In-Reply-To: <08cb075e-018c-474e-abd4-b76ba1ed6a52@linaro.org> Date: Tue, 17 Nov 2020 10:05:15 +0000 Message-ID: Subject: Re: [PATCH v3 07/24] Documentation for memory tagging remote packets To: Luis Machado Content-Type: text/plain; charset="UTF-8" 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: , From: David Spickett via Gdb-patches Reply-To: David Spickett Cc: gdb-patches@sourceware.org Errors-To: gdb-patches-bounces@sourceware.org Sender: "Gdb-patches" > Right now the design makes these types architecture-specific. This works too, in fact it matches the breakpoint types example better that way. > But there's one catch right now. The user-visible commands know about > two types of tags (logical and allocation). The native/remote side of > GDB only sees one type, the allocation one, as it doesn't make sense to > ask the native/remote target about logical tags. > > This is slightly messy and, in my opinion, should be an implementation > detail. Tell me if I have this right. In gdb in overall you have these two types but the server only uses one of them, the allocation tag type. So only the allocation tag type will ever go over the protocol. (for MTE at least) Given that, if we assume that "mte allocation" type is 1. A future AArch64 kind of memory tagging could allocate 2 and on for its tag types. Something like: AArch64 Memory Tag types - 0 : MTE logical (which is internal only, reserved but documented as unused, or left out completely?) 1 : MTE allocation (the one we use at present) 2: logical tag (because maybe there is some server component for this kind of tagging extension?) 3: allocation tag The reason I want to clarify is that I understood the type to differentiate tagging technologies, not the kind of tag within them. (the type tells you MTE vs instead of allocation vs logical) The use case being what if you have MTE and active in the same target and I want to set an MTE allocation tag, how can the server tell them apart? If the type numbers overlap between tagging technologies, we can't tell them apart. However if they encode what extension they are for and the logical/allocation type (as in the example above) then we can. A lot of that is probably academic given there's one relevant type but we can at least document the intent of the field. E.g. "these types are global to AArch64 so new types should not overlap existing ones" > Otherwise we'd need to standardize on particular tag type names across > different architectures, like "hw memory tag", "sw memory tag", > "capability tag" etc. Well I was thinking of type more as a single value like "mte". Anyway I'm fine with the integer route. On Mon, 16 Nov 2020 at 17:23, Luis Machado wrote: > > > > On 11/16/20 1:04 PM, David Spickett wrote: > > Also with regard to the "type" field. > > > >> +@var{type} is the type of tag the request wants to fetch. The typeis a signed > >> +integer. > > > > (typo aside) Is this field architecture specific and will there be a > > list of these type numbers documented anywhere? (or already is) > > For example would 1 on AArch64 be MTE, and on be > tag type>. Or would that be 2. > > > > My assumption has been that it is the latter and that a value means a > > kind of tagging extension. So for example 1=MTE rather than > > 1= mte logical and 2 = mte allocation. Correct me if I am wrong there. > > Right now the design makes these types architecture-specific. It would > be nice to have more documentation about them, for sure. > > But there's one catch right now. The user-visible commands know about > two types of tags (logical and allocation). The native/remote side of > GDB only sees one type, the allocation one, as it doesn't make sense to > ask the native/remote target about logical tags. > > This is slightly messy and, in my opinion, should be an implementation > detail. > > So, in summary... We have a couple generic tag types GDB knows about: > logical and allocation. > > Those types get translated to an arch/a target-specific type when they > cross the native/remote target boundary. > > In theory we could have generic tag types 1 and 2 in generic code, but > tag type 2 gets translated to type 1 in a remote packet. > > Maybe we could improve this a little. > > > > > A page like: > > https://sourceware.org/gdb/current/onlinedocs/gdb/ARM-Breakpoint-Kinds.html#ARM-Breakpoint-Kinds > > > > Or just a short note, given that there's only one type right now. > > Yes, that would be nice to expand for the tag types. > > > > > Also, I may have suggested the type be a string at some point. However > > based on examples like the link above > > I don't see much advantage to it apart from making packet dumps easier > > to read. Just wanted to close the loop on that > > if I didn't before. > > I don't have a strong preference here. I'm just forwarding the tag type > from generic code. > > If we want to pass strings, we will need a gdbarch hook that maps a type > to a string in the remote target layer. > > Otherwise we'd need to standardize on particular tag type names across > different architectures, like "hw memory tag", "sw memory tag", > "capability tag" etc. > > > > > > > > > On Mon, 16 Nov 2020 at 15:44, David Spickett wrote: > >> > >> Minor thing, there is a missing space here in "typeis". > >> > >>> +@var{type} is the type of tag the request wants to fetch. The typeis a signed > >>> +integer. > >> > >> On Mon, 9 Nov 2020 at 17:08, Eli Zaretskii wrote: > >>> > >>>> Date: Mon, 9 Nov 2020 14:04:18 -0300 > >>>> From: Luis Machado via Gdb-patches > >>>> Cc: david.spickett@linaro.org > >>>> > >>>> gdb/doc/ChangeLog: > >>>> > >>>> YYYY-MM-DD Luis Machado > >>>> > >>>> * gdb.texinfo (General Query Packets): Document qMemTags and > >>>> QMemTags. Document the "memory-tagging" feature. > >>>> --- > >>>> gdb/doc/gdb.texinfo | 96 +++++++++++++++++++++++++++++++++++++++++++++ > >>>> 1 file changed, 96 insertions(+) > >>> > >>> OK for this part, thanks.