Date: Mon, 24 Jul 2017 19:40:57 -0700 From: Kees Cook <keescook@...omium.org> To: Hans Liljestrand <liljestrandh@...il.com> 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 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). -Kees -- Kees Cook Pixel Security
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