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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id k98sm476660pjb.42.2020.07.22.12.42.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Jul 2020 12:42:51 -0700 (PDT) Date: Wed, 22 Jul 2020 12:42:50 -0700 From: Kees Cook To: Josh Poimboeuf Cc: Miroslav Benes , Kristen Carlson Accardi , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, arjan@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, live-patching@vger.kernel.org Subject: Re: [PATCH v4 00/10] Function Granular KASLR Message-ID: <202007221241.EBC2215A@keescook> References: <20200717170008.5949-1-kristen@linux.intel.com> <202007220738.72F26D2480@keescook> <20200722160730.cfhcj4eisglnzolr@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200722160730.cfhcj4eisglnzolr@treble> Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Wed, Jul 22, 2020 at 11:07:30AM -0500, Josh Poimboeuf wrote: > On Wed, Jul 22, 2020 at 07:39:55AM -0700, Kees Cook wrote: > > On Wed, Jul 22, 2020 at 11:27:30AM +0200, Miroslav Benes wrote: > > > Let me CC live-patching ML, because from a quick glance this is something > > > which could impact live patching code. At least it invalidates assumptions > > > which "sympos" is based on. > > > > In a quick skim, it looks like the symbol resolution is using > > kallsyms_on_each_symbol(), so I think this is safe? What's a good > > selftest for live-patching? > > The problem is duplicate symbols. If there are two static functions > named 'foo' then livepatch needs a way to distinguish them. > > Our current approach to that problem is "sympos". We rely on the fact > that the second foo() always comes after the first one in the symbol > list and kallsyms. So they're referred to as foo,1 and foo,2. Ah. Fun. In that case, perhaps the LTO series has some solutions. I think builds with LTO end up renaming duplicate symbols like that, so it'll be back to being unique. -- Kees Cook