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 X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 136A7C433EF for ; Tue, 14 Sep 2021 20:32:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E92D060FED for ; Tue, 14 Sep 2021 20:32:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233749AbhINUeE (ORCPT ); Tue, 14 Sep 2021 16:34:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233373AbhINUeE (ORCPT ); Tue, 14 Sep 2021 16:34:04 -0400 Received: from mail-yb1-xb2d.google.com (mail-yb1-xb2d.google.com [IPv6:2607:f8b0:4864:20::b2d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B97F0C061762 for ; Tue, 14 Sep 2021 13:32:46 -0700 (PDT) Received: by mail-yb1-xb2d.google.com with SMTP id s16so960595ybe.0 for ; Tue, 14 Sep 2021 13:32:46 -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=NfCs5ZOjiQwn8561ZlGnTqyiRoY51Z30liszO8UxNQY=; b=bcaWNiUmkwe6O+wIIy65AytawNojw83SBP2fQAkZFCKkQ5m+UNFh0SVKHeD9Tm1HWZ uszQabEJWi/OVKkhLwFZ/uNCVq8TzahJNZw9ppPmCbAEUQB2vDg3TQVBX9DdqWtpVwCF gTqrSnuoKk/jMCmAa9FJQJQ+DNoRoZMNeCPDGnYOUSHcRVOraJl7ATFALh7PSCmA3wWu NyvyLzKhIiCtq3ajsnqBaDoPgUtHKvvedNtdzWc675nYfwyakomLkU6Nte03hO+q+vrZ Foy8xooQQ7u9C47j5IHKWFwNSvWfimfm9OxmHEyF22wdToYgkTjWQI+RyNUPqPZj2DWx cj/Q== 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=NfCs5ZOjiQwn8561ZlGnTqyiRoY51Z30liszO8UxNQY=; b=ogJCDvbWI4j8CX+Vl+/yydMaizB0PAD/eLsZ9TDg20lOR3qheqdjKRQKeInWr0A8Jb EwtX3lfN/VVaTRcnPbyyKjfvgkreIhI5QUAjuVqbdVp91t/jsm9RgbEhxQHq9U3hMya6 /TLIPjaYgcyEYDfWQWNB9Atwo+rB8a7WCM5nPb/kgZfEg3I+b+5AE1uxrxa8M5Tmuk7C npmG1tBGfsqBwXWdlmlUmhRCkUWlUVHrg6uoPLW40yosMTm9jDpWIcf58+o2FOSSCRwk Gxs7f2plv4BbVdesOX38qgggAQm4ELBQL7PT5FlIhIYvjplOmVcqKsott/ohfbqlyCXn FpUQ== X-Gm-Message-State: AOAM531XZDK2lRbrpy+kY45/b66AVyoI7jSP7jAbBOGQLZRpg/e9ea5U JiNoA5rpQMMuS+90QUF/1cBz2I5mg+s0XA29TGl1Nw== X-Google-Smtp-Source: ABdhPJxIvcMD+L8IGnxkRjwWdcD9kMSbk077KA22bPLKMcWA4LzDlbScguPptlpzJDanrJWpmENcGDtAzzfrX1U2RdM= X-Received: by 2002:a25:2142:: with SMTP id h63mr1475940ybh.70.1631651565763; Tue, 14 Sep 2021 13:32:45 -0700 (PDT) MIME-Version: 1.0 References: <20210914191045.2234020-1-samitolvanen@google.com> <20210914191045.2234020-5-samitolvanen@google.com> In-Reply-To: From: Sami Tolvanen Date: Tue, 14 Sep 2021 13:32:34 -0700 Message-ID: Subject: Re: [PATCH v3 04/16] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB To: Nick Desaulniers Cc: X86 ML , Kees Cook , Josh Poimboeuf , Peter Zijlstra , Nathan Chancellor , Sedat Dilek , linux-hardening@vger.kernel.org, LKML , clang-built-linux Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Tue, Sep 14, 2021 at 12:36 PM Nick Desaulniers wrote: > > On Tue, Sep 14, 2021 at 12:10 PM Sami Tolvanen wrote: > > > > This change introduces the DEFINE_CFI_IMMEDIATE_RETURN_STUB macro, > > which defines a stub function that immediately returns and when > > defined in the core kernel, always passes indirect call checking > > with CONFIG_CFI_CLANG. Note that this macro should only be used when > > a stub cannot be called using the correct function type. > > > > Signed-off-by: Sami Tolvanen > > --- > > include/asm-generic/vmlinux.lds.h | 11 +++++++++++ > > include/linux/cfi.h | 14 ++++++++++++++ > > kernel/cfi.c | 24 +++++++++++++++++++++++- > > 3 files changed, 48 insertions(+), 1 deletion(-) > > > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > > index f2984af2b85b..5b77284f7221 100644 > > --- a/include/asm-generic/vmlinux.lds.h > > +++ b/include/asm-generic/vmlinux.lds.h > > @@ -407,6 +407,16 @@ > > KEEP(*(.static_call_tramp_key)) \ > > __stop_static_call_tramp_key = .; > > > > +#ifdef CONFIG_CFI_CLANG > > +#define CFI_EXCLUDED_DATA \ > > + . = ALIGN(8); \ > > + __start_cfi_excluded = .; \ > > + KEEP(*(.cfi_excluded_stubs)) \ > > + __stop_cfi_excluded = .; > > +#else > > +#define CFI_EXCLUDED_DATA > > +#endif > > + > > /* > > * Allow architectures to handle ro_after_init data on their > > * own by defining an empty RO_AFTER_INIT_DATA. > > @@ -430,6 +440,7 @@ > > __start_rodata = .; \ > > *(.rodata) *(.rodata.*) \ > > SCHED_DATA \ > > + CFI_EXCLUDED_DATA \ > > RO_AFTER_INIT_DATA /* Read only after init */ \ > > . = ALIGN(8); \ > > __start___tracepoints_ptrs = .; \ > > diff --git a/include/linux/cfi.h b/include/linux/cfi.h > > index 879744aaa6e0..9ebf67a0d421 100644 > > --- a/include/linux/cfi.h > > +++ b/include/linux/cfi.h > > @@ -20,6 +20,18 @@ extern void __cfi_check(uint64_t id, void *ptr, void *diag); > > #define __CFI_ADDRESSABLE(fn, __attr) \ > > const void *__cfi_jt_ ## fn __visible __attr = (void *)&fn > > > > +/* > > + * Defines a stub function that returns immediately, and when defined and > > + * referenced in the core kernel, always passes CFI checking. This should > > + * be used only for stubs that cannot be called using the correct function > > + * pointer type, which should be rare. > > + */ > > +#define DEFINE_CFI_IMMEDIATE_RETURN_STUB(fn) \ > > + void fn(void) { return; } \ > > + const void *__cfi_excl_ ## fn __visible \ > > + __attribute__((__section__(".cfi_excluded_stubs"))) \ > > Can we use __section from include/linux/compiler_attributes.h here > rather than open coding the function attribute? Sure. I'll change this in v4. Sami