From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2731E135A4B; Thu, 13 Jun 2024 06:12:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718259122; cv=none; b=RvgMbT9V5qZglIEeXXGvHRZZgOCXt5Xpmq9hV8xl8+UeywhrXYEc2L319vNKRoScQENWnXOXZf8pwzaCCeyaWCWz1+adeYk0w1g39n3kkfefPH2pbQa4jQc+mJRwHm3OIe2O0tADqEB2Z0POm89EiJmjiBdmbPxdnE+GvJd3v6E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718259122; c=relaxed/simple; bh=2tfIxnfDqiV8m2eUOgIRXcgva0U3ORhh129cB7f/07Y=; h=MIME-Version:References:In-Reply-To:From:Date:Message-ID:Subject: To:Cc:Content-Type; b=FMYfvKI4y3cOKWZDwUxgYCwqb8dO/QbtXDLLrkQgvBZ2ngtgIhNOWV2414flntPgsmPteZDEt/StyUzPGeeRDugH+dYlF5voevpcStLyCVvYzRFJNm/WJTWz+HUPyPlISqL0IayIalgRyrtQrKhEaIaQK7LAzjVBDumaOYmkMZE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aLMc62CM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aLMc62CM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B62D6C4AF5F; Thu, 13 Jun 2024 06:12:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1718259121; bh=2tfIxnfDqiV8m2eUOgIRXcgva0U3ORhh129cB7f/07Y=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=aLMc62CMcYbhlI0BxA1bmCKIFpC7d6uUNzAaYgoMqzg59/gCWcohnthbnkHm3+PuL zVtwTkOMcMOvC7TikDQsC/2VSZMAFRluA1HBDadue43vDev0PzLlvojOLhhkNE1YCg ex0oFd7VBGibaU6QGkqbCRvkNW6/ksv7xrRJ5lEsQ83WEsxJKkJWb4mTGWG3N/K9QA Javtf6isZCNRW3fAseXH79Ym7TvCN4tEredwd9vy0ftIPHqUwvY2N3dddOOUW95Rbv XoB1GELyN67C3bG8sUp7ZHz7I499XFVQKJJ4mMRS5J7xQEgFSJU9bmkPkIsS8G4zhH lkCItH0cnFioQ== Received: by mail-lf1-f41.google.com with SMTP id 2adb3069b0e04-52c7f7fdd24so937540e87.1; Wed, 12 Jun 2024 23:12:01 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCUDNxy4lrQpweYxTY4V9BSZiB+J6aTiZkzC1kadm70Vx4fg4X819O/pobF4Cg+YF6jCTspFq/dK0FZckVI2MEv7N1rVed0XwAVh74r3xT5HYk4rLz5lMnfF6kpHPrxaFMD7Zr/yWMVGwh86KqehkC2rWenxnXSdRMT+nao/Wxd3B56EZBMrsMLB4ThezY2jg951 X-Gm-Message-State: AOJu0Yx1KIHlneXm5/rZ59Bjvbxv8N91tiosXzCM1Gdl7pC5cIbQQkaW nIIYBIu+XVidJsqnVHOi7KvZGe0Hde+XWndf5Pb2nNHJ6ATAr9MdG1E0VpvPZoeiTR+CFUiXNzn DOV61wV5Ge0T+vE+pGH8KKzP7xVc= X-Google-Smtp-Source: AGHT+IFdLbYZojyhqvDEXOP8w6OnQtiDQDSpYwdN44bj4F4g15wPRxlf8c6AOb6GWfv8yK5ap3XFShBJ/euTC9+lXSo= X-Received: by 2002:ac2:4a82:0:b0:52b:cb05:ed46 with SMTP id 2adb3069b0e04-52c9a3c79a1mr2099464e87.21.1718259119855; Wed, 12 Jun 2024 23:11:59 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20240611144911.327227285@goodmis.org> <20240611144949.703297941@goodmis.org> <202406121145.8860502D7@keescook> <20240612145228.5bf426e0@rorschach.local.home> In-Reply-To: From: Ard Biesheuvel Date: Thu, 13 Jun 2024 08:11:48 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 2/2] pstore/ramoops: Add ramoops.mem_name= command line option To: Mike Rapoport Cc: Steven Rostedt , Kees Cook , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , linux-mm@kvack.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Tony Luck , "Guilherme G. Piccoli" , linux-hardening@vger.kernel.org, Guenter Roeck , Ross Zwisler , wklin@google.com, Vineeth Remanan Pillai , Joel Fernandes , Suleiman Souhlal , Linus Torvalds , Catalin Marinas , Will Deacon Content-Type: text/plain; charset="UTF-8" On Thu, 13 Jun 2024 at 08:04, Mike Rapoport wrote: > > On Wed, Jun 12, 2024 at 02:52:28PM -0400, Steven Rostedt wrote: > > On Wed, 12 Jun 2024 11:45:57 -0700 > > Kees Cook wrote: > > > > > On Tue, Jun 11, 2024 at 10:49:13AM -0400, Steven Rostedt wrote: > > > > From: "Steven Rostedt (Google)" > > > > > > > > Add a method to find a region specified by reserve_mem=nn:align:name for > > > > ramoops. Adding a kernel command line parameter: > > > > > > > > reserve_mem=12M:4096:oops ramoops.mem_name=oops > > > > > > > > Will use the size and location defined by the memmap parameter where it > > > > finds the memory and labels it "oops". The "oops" in the ramoops option > > > > is used to search for it. > > > > > > > > This allows for arbitrary RAM to be used for ramoops if it is known that > > > > the memory is not cleared on kernel crashes or soft reboots. > > > > > > > > Signed-off-by: Steven Rostedt (Google) > > > > > > Acked-by: Kees Cook > > > > > > Let me know if this should go via the pstore tree, if you'd rather carry > > > it? > > > > > > > I'm going to send out another version to cover some more comments that > > were made, and perhaps it's best if Mike Rapoport takes it through his > > tree. > > I've added one more comment to v5, with that fixed I can take this. > So how is this supposed to work wrt to the rigid 'no user visible regressions' rule, given that this whole thing is a best effort thing to begin with. This needs at least a huge disclaimer that this rule does not apply, and if this works today, there is no guarantee that it will keep working on newer kernels. Otherwise, you will be making the job of the people who work on the boot code significantly more difficult. And even then, I wonder whether Linus and #regzcop are going to honour such a disclaimer. So this belongs downstream, unless some guarantees can be provided that this functionality is exempt from the usual regression policies.