Date: Tue, 25 Jul 2017 10:16:38 +0300 From: Hans Liljestrand <liljestrandh@...il.com> To: Kees Cook <keescook@...omium.org> Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, "Reshetova, Elena" <elena.reshetova@...el.com>, Dave Hansen <dave.hansen@...el.com>, "H. Peter Anvin" <hpa@...or.com> Subject: Re: [RFC PATCH 2/5] gcc-plugins: adds MPXK gcc plugin On Mon, Jul 24, 2017 at 07:40:57PM -0700, Kees Cook wrote: >On Mon, Jul 24, 2017 at 6:38 AM, Hans Liljestrand ><liljestrandh@...il.com> wrote: >> Adds a gcc-plugin that modifies vanilla GCC MPX instrumentation for >> in-kernel use. Also adds MPXK_CFLAGS Makefile variable that can be used to >> selectively enable MPXK for specific kernel objects. This plugin is not >> enabled kernel-wide and must be explicitly enabled in the appropriate >> Makefile. >> >> The purpose of the plugin is to replace BNDSTX+BNDLDX bound storage with >> our own mpxk_load_bounds function and to replace memory mainpulating >> function with corresponding wrapper function. The plugin accomplishes >> this via the following tasks: >> >> - It adds MPXK-wrappers functions for memory altering functions, e.g. >> kmalloc, memcpy, etc. This is needed both to check bounds for input >> argument pointers and properly set bounds for returned pointers. This >> is done by the mpxk_wrappers compiler pass. (This could potentially >> be done, for better performance, by direct instrumentation at the call >> site.) >> >> - Replace BNDLDX calls with mpxk_load_bounds function calls. This >> includes two separate cases: free-standing loads handled by the >> mpxk_bnd_store pass, and loads in function prologues that are handled >> by the mpxk_cfun_args pass. These are needed for situation where the >> compile time instrumentation cannot determine a way to statically >> propagate the bounds via the stack or registers. >> >> - The final mpxk_pass_sweeper removes any remaining BNDLDX/BNDSTX calls. > >Since this creates multiple files for a single plugin, can you instead >relocate these into a subdirectory (which should be supported by the >build system already). Thanks. I was a bit unsure how to organize these in the first place, but a subdirectory sounds like a good idea. I'll also look at consolidating the non-pass files into one. Regards, -hans > >-Kees > >-- >Kees Cook >Pixel Security
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