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[2620:137:e000::1:20]) by mx.google.com with ESMTP id n1-20020a170906688100b006cd5fc9f21esi3239702ejr.543.2022.02.26.07.21.43; Sat, 26 Feb 2022 07:22:19 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=desiato.20200630 header.b=ieGeELfF; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231536AbiBZLtz (ORCPT + 99 others); Sat, 26 Feb 2022 06:49:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230151AbiBZLty (ORCPT ); Sat, 26 Feb 2022 06:49:54 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3011A26372D for ; Sat, 26 Feb 2022 03:49:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=UlDCQiGwaD/6NgzvxKMYssO1Vg316rUDPKnel4O4TSg=; b=ieGeELfFyjZfFKdVB17t3WXAr+ m+NwaZ7B9F2M7YCySM5WyucRLGiTsTcfLwZMWnEpkfffA2zm9TkoG0Yn0ohQ1gVFx88pD/RZO/skt Jse63zSp3ik4iZ/1rx1eZqJS86bmfqWZA+XilgKbxxn5S70qBdfn5X0PvHUu+f1OZAbOYN3+ChdB/ HzEEnB2pEIyipDFlQ6YQgZLxNWx42V6Jq1K9ax8DHDRfup/9c9wV/YYwWo8X1T2hxi5ok3zqGE+7T Rsl06GgQq5XVkDzCyubaeRfJND7B9tRSDVo5XgIpoNBdlRq3hIMHnTj28RSpjeRzfMRt5NuaaKAgq 4vzZSxcA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nNvZB-00DCsT-5v; Sat, 26 Feb 2022 11:48:49 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 633C1986AEC; Sat, 26 Feb 2022 12:48:47 +0100 (CET) Date: Sat, 26 Feb 2022 12:48:47 +0100 From: Peter Zijlstra To: Masami Hiramatsu Cc: x86@kernel.org, joao@overdrivepizza.com, hjl.tools@gmail.com, jpoimboe@redhat.com, andrew.cooper3@citrix.com, linux-kernel@vger.kernel.org, ndesaulniers@google.com, keescook@chromium.org, samitolvanen@google.com, mark.rutland@arm.com, alyssa.milburn@intel.com, mbenes@suse.cz, rostedt@goodmis.org, alexei.starovoitov@gmail.com Subject: Re: [PATCH v2 15/39] x86/ibt,kprobes: Fix more +0 assumptions Message-ID: <20220226114847.GB11184@worktop.programming.kicks-ass.net> References: <20220224145138.952963315@infradead.org> <20220224151322.892372059@infradead.org> <20220225103215.77080de0b3edd0fa2839b8fa@kernel.org> <20220225224249.cbabe82e530758cdb28e65e9@kernel.org> <20220226111040.49b6b82a6c0caebee8c6d552@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220226111040.49b6b82a6c0caebee8c6d552@kernel.org> X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 26, 2022 at 11:10:40AM +0900, Masami Hiramatsu wrote: > > The alternative 'hack' I've been contemplating is (ab)using > > INT_MIN/INT_MAX offset for __fentry__ and __fexit__ points (that latter > > is something we'll probably have to grow when CET-SHSTK or backward-edge > > CFI gets to be done, because then ROP tricks as used by function-graph > > and kretprobes are out the window). > > > > That way sym+[0..size) is still a valid reference to the actual > > instruction in the symbol, but sym+INT_MIN will hard map to __fentry__ > > while sym+INT_MAX will get us __fexit__. > > Interesting, is that done by another series? Not yet, that was just a crazy idea I had ;-)