From sacadmin Tue Dec 19 11:22:24 2006 Received: from jurassic.eng.sun.com (jurassic.SFBay.Sun.COM [129.146.226.130]) by sac.sfbay.sun.com (8.13.6+Sun/8.13.6) with ESMTP id kBJJMOY6015019 for ; Tue, 19 Dec 2006 11:22:24 -0800 (PST) Received: from [129.146.226.100] (chaz.SFBay.Sun.COM [129.146.226.100]) by jurassic.eng.sun.com (8.13.8+Sun/8.13.8) with ESMTP id kBJJMMPI666545 for ; Tue, 19 Dec 2006 11:22:22 -0800 (PST) Message-ID: <45883BA7.4030207@sun.com> Date: Tue, 19 Dec 2006 11:21:11 -0800 From: Rod Evans Reply-To: Rod.Evans@sun.com Organization: Sun Microsystems Inc. User-Agent: Mail/News 1.5.0.4 (X11/20060731) MIME-Version: 1.0 To: psarc@sac.sfbay.sun.com Subject: 2006/714: ld(1) mapfile: symbol interpose definition Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Status: RO Content-Length: 1980 I'm sponsoring the following case for myself. This case qualifies for Architectural self-review, but I wish to record the following information. ------------------------------------------------------------------------ An object can be defined to be an interposer using ld(1)'s -zinterpose option. This option results in all global symbols offered by the object to act as interposers. Identifying interposers is important within a directly-bound environment as this identification ensures the interposer intercepts any directly-bound symbol binding. Work on direct bindings has uncovered numerous applications that provide one or two symbols that act as interposers. Identifying the whole object as -zinterpose is a rather large hammer, as the evolution of the dependencies of these applications may result in additional symbols acting as interposers when this was not the intent of the original application designed. ie. an application defines foo() and bar(), and foo() is intended to interpose on libc's version of foo(). bar() is simply used by the application. libc gets updated with a new interface bar(). The application will now interpose on bar(). ------------------------------------------------------------------------ A new mapfile symbol directive will allow individual symbols within a dynamic executable to be identified as interposers: { global: foo = INTERPOSE; }; At runtime, should direct bindings be in effect, any interposer is first inspected to determine if an appropriate binding can be established. An application that has been built with INTERPOSE directives will allow just the symbols defined as interposers to intercept any direct bindings. Other global symbols within the application will remain available to any standard symbol search as they are today. ------------------------------------------------------------------------ Release Binding: Patch/Micro mapfile INTERPOSE directive Committed -- Rod.