From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF8A6C433EF for ; Fri, 10 Jun 2022 23:44:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351205AbiFJXoI (ORCPT ); Fri, 10 Jun 2022 19:44:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351204AbiFJXoG (ORCPT ); Fri, 10 Jun 2022 19:44:06 -0400 Received: from mail-lf1-x134.google.com (mail-lf1-x134.google.com [IPv6:2a00:1450:4864:20::134]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B4623F466D for ; Fri, 10 Jun 2022 16:44:03 -0700 (PDT) Received: by mail-lf1-x134.google.com with SMTP id w20so731564lfa.11 for ; Fri, 10 Jun 2022 16:44:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=0LsNMVk4QkQcHLkW7ut/k0O0Yaykk6wclPSmWZ5ifsY=; b=AXZAoRjCkVTGzxCFmAzh/oJWaoE94oMVuck4U6PkHFXm8Manqvzoox91KP0798a6Vm Iif2fnd5/zxMLU0WowWFmFD02PIvRdYbdM8AOKWN07FLf7W3i8ZgvaVIN6ZqOrxJi+Q+ SNwkOFBnJdiJ/iMD4ZIHySibtDyYLWJnDV2Jl+l/OlObxnNJPZ+Gp3oKP77OD8CHjZwZ K23us6sh34xesB0jnd7qxO7B7+aQb/9BDyvvn90C40zKoUSvdukZv2F1wed/pqp4HhyW RyYE0sGw1Hex9gbwwYSWvCdaNw4UJ2EJraztGTA91vxlzFCYZr6g/lyW+aOzEEe+E3Xp PqJA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=0LsNMVk4QkQcHLkW7ut/k0O0Yaykk6wclPSmWZ5ifsY=; b=q2Tlmx31wTIKf/pTX4xpCmPH+r79/0NYPkPCYpPmMYpxoQ3XPdREsPLoEvc4LU3ffs OZ+RowmA71PDYazhEYsBS13Ga+qUoX7a8hj1XBop94UTXs3+aQQYfKLhsB6Bm77ev8CQ 4nMAhXDxka5LVy5eJQkyWg+/JtqBlLELlHIg4moL+1ZmUGlD5etRef7tcN7APSqQX5AR iw+KQwcdORUzS5+AapGdpF8lYjwdXyL32bCv81rSRQ62aKRGmjBeYwwgNP7rmH/g1Ev1 wRPePQteshvXLPrq0gjzD1G2WXl36/5VNklqvj6C7MCcboI+Uoft3lYkBSc1XS3PHgRn tObg== X-Gm-Message-State: AOAM532h4W9iapbBe99giOwO1f8qyQYw38Unb9A6ygw3AdKyGbUAZuMs 0f5LvJBd3k02rari9l1nZ+DIKpPHr6064tZtPX91dw== X-Google-Smtp-Source: ABdhPJzmnqMLhs1bfP/6LgEEcErMYRF7zruVcTTGgghAvhoIJQutFqUZdi12symO64L5cd0aKgb51yl0Fh7DWLzLDco= X-Received: by 2002:a05:6512:3f94:b0:478:7abe:de4a with SMTP id x20-20020a0565123f9400b004787abede4amr63212721lfa.401.1654904641567; Fri, 10 Jun 2022 16:44:01 -0700 (PDT) MIME-Version: 1.0 References: <20220610233513.1798771-1-samitolvanen@google.com> <20220610233513.1798771-8-samitolvanen@google.com> In-Reply-To: <20220610233513.1798771-8-samitolvanen@google.com> From: Nick Desaulniers Date: Fri, 10 Jun 2022 16:43:50 -0700 Message-ID: Subject: Re: [RFC PATCH v3 07/20] lkdtm: Emit an indirect call for CFI tests To: Sami Tolvanen Cc: LKML , Kees Cook , Josh Poimboeuf , Peter Zijlstra , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Catalin Marinas , Will Deacon , Mark Rutland , Nathan Chancellor , Joao Moreira , Sedat Dilek , Steven Rostedt , linux-hardening@vger.kernel.org, Linux ARM , clang-built-linux Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 10, 2022 at 4:35 PM Sami Tolvanen wrote: > > Clang can convert the indirect calls in lkdtm_CFI_FORWARD_PROTO into > direct calls. Move the call into a noinline function that accepts the > target address as an argument to ensure the compiler actually emits an > indirect call instead. Thanks for the patch! Reviewed-by: Nick Desaulniers > > Signed-off-by: Sami Tolvanen > --- > drivers/misc/lkdtm/cfi.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/drivers/misc/lkdtm/cfi.c b/drivers/misc/lkdtm/cfi.c > index 666a7f4bc137..b6b375112a2a 100644 > --- a/drivers/misc/lkdtm/cfi.c > +++ b/drivers/misc/lkdtm/cfi.c > @@ -20,6 +20,13 @@ static noinline int lkdtm_increment_int(int *counter) > > return *counter; > } > + > +/* Don't allow the compiler to inline the calls. */ > +static noinline void lkdtm_indirect_call(void (*func)(int *)) > +{ > + func(&called_count); > +} > + > /* > * This tries to call an indirect function with a mismatched prototype. > */ > @@ -29,15 +36,11 @@ static void lkdtm_CFI_FORWARD_PROTO(void) > * Matches lkdtm_increment_void()'s prototype, but not > * lkdtm_increment_int()'s prototype. > */ > - void (*func)(int *); > - > pr_info("Calling matched prototype ...\n"); > - func = lkdtm_increment_void; > - func(&called_count); > + lkdtm_indirect_call(lkdtm_increment_void); > > pr_info("Calling mismatched prototype ...\n"); > - func = (void *)lkdtm_increment_int; > - func(&called_count); > + lkdtm_indirect_call((void *)lkdtm_increment_int); > > pr_err("FAIL: survived mismatched prototype function call!\n"); > pr_expected_config(CONFIG_CFI_CLANG); > -- > 2.36.1.476.g0c4daa206d-goog > -- Thanks, ~Nick Desaulniers