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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 7F4D4C433E0 for ; Fri, 31 Jul 2020 23:10:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5818920836 for ; Fri, 31 Jul 2020 23:10:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="ChTbXvzs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728332AbgGaXKB (ORCPT ); Fri, 31 Jul 2020 19:10:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726535AbgGaXIf (ORCPT ); Fri, 31 Jul 2020 19:08:35 -0400 Received: from mail-pj1-x1043.google.com (mail-pj1-x1043.google.com [IPv6:2607:f8b0:4864:20::1043]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 159A7C06179F for ; Fri, 31 Jul 2020 16:08:35 -0700 (PDT) Received: by mail-pj1-x1043.google.com with SMTP id ha11so8527872pjb.1 for ; Fri, 31 Jul 2020 16:08:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=/YhwjFJ10iSnqHVnH+E/18OCqFOxfL3O8briALHREkQ=; b=ChTbXvzsXUQoQlCmz5X8Q1Gxp3riiGCK1dNfhc3GaXY/yjlrWcZZYXu3uehyV0TVAH ihRqgWMrLH5jMadKjfk+FVyA1FEBsJSXXfWVEbqpLeRYsVNgrnwSPBcfSC73bZJhBxa1 JLaP+A64JNtfY9YvLrYFKoPvej2TJRx4yZ0es= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=/YhwjFJ10iSnqHVnH+E/18OCqFOxfL3O8briALHREkQ=; b=LK5nmRfL/IaAV9KfUVP7r6YfTg9FPGP/KqQfio6fQ+WHd4qMR1vSdF+QqZacwXLjLt vICtP7QA6rrPGmoBhhDqhbNHW9CItsjXz+Q6zBtmubD1aiF7ZCw//MgDn21gwqhG640C YI8hVUOynt7qTzntrpC+ZctOAIzMgaDocEcQCdwBsOZwGS9kqU3qkq6KOuX4tGdMAztv 68LZEZyIBC00cXssbIJxWUHPLiAa92ARovPUIC6WVqdtljOs/TU7qTrWBc0ATbFwOgFx si+6GM4CF7BtIGFFAPFduF5VjGbMP2kSfjIbhtlLcMCmx6GePWLbeHfK1Ftk+dx9I80l pdDQ== X-Gm-Message-State: AOAM533p9lN1nOD15C2mvuLO2OAcnEduxS+m0BsNYLScEp3yceGD0X3t d5Lh/k+dNFK4lhDk3fJC9j691w== X-Google-Smtp-Source: ABdhPJyiEsFmEcCe1WG+hFmLyNannOXDGWZ7/pGsnQqAo6NQ22CMiVZ00GK9pyuWatNfeet0DIr+ZA== X-Received: by 2002:a17:90a:1aee:: with SMTP id p101mr2914247pjp.138.1596236914544; Fri, 31 Jul 2020 16:08:34 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id b22sm9843692pju.26.2020.07.31.16.08.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 31 Jul 2020 16:08:30 -0700 (PDT) From: Kees Cook To: Thomas Gleixner , Will Deacon Cc: Kees Cook , Ard Biesheuvel , Arvind Sankar , Sedat Dilek , Nick Desaulniers , Catalin Marinas , Mark Rutland , Peter Collingbourne , James Morse , Borislav Petkov , Ingo Molnar , Russell King , Masahiro Yamada , Nathan Chancellor , Arnd Bergmann , x86@kernel.org, clang-built-linux@googlegroups.com, linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 01/36] x86/boot/compressed: Move .got.plt entries out of the .got section Date: Fri, 31 Jul 2020 16:07:45 -0700 Message-Id: <20200731230820.1742553-2-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200731230820.1742553-1-keescook@chromium.org> References: <20200731230820.1742553-1-keescook@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ard Biesheuvel The .got.plt section contains the part of the GOT which is used by PLT entries, and which gets updated lazily by the dynamic loader when function calls are dispatched through those PLT entries. On fully linked binaries such as the kernel proper or the decompressor, this never happens, and so in practice, the .got.plt section consists only of the first 3 magic entries that are meant to point at the _DYNAMIC section and at the fixup routine in the loader. However, since we don't use a dynamic loader, those entries are never populated or used. This means that treating those entries like ordinary GOT entries, and updating their values based on the actual placement of the executable in memory is completely pointless, and we can just ignore the .got.plt section entirely, provided that it has no additional entries beyond the first 3 ones. So add an assertion in the linker script to ensure that this assumption holds, and move the contents out of the [_got, _egot) memory range that is modified by the GOT fixup routines. While at it, drop the KEEP(), since it has no effect on the contents of output sections that are created by the linker itself. Signed-off-by: Ard Biesheuvel Signed-off-by: Arvind Sankar Tested-by: Sedat Dilek Tested-by: Nick Desaulniers Reviewed-by: Kees Cook Acked-by: Arvind Sankar Link: https://lore.kernel.org/r/20200523120021.34996-2-ardb@kernel.org Signed-off-by: Kees Cook --- arch/x86/boot/compressed/vmlinux.lds.S | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S index 8f1025d1f681..b17d218ccdf9 100644 --- a/arch/x86/boot/compressed/vmlinux.lds.S +++ b/arch/x86/boot/compressed/vmlinux.lds.S @@ -44,10 +44,13 @@ SECTIONS } .got : { _got = .; - KEEP(*(.got.plt)) KEEP(*(.got)) _egot = .; } + .got.plt : { + *(.got.plt) + } + .data : { _data = . ; *(.data) @@ -77,3 +80,9 @@ SECTIONS DISCARDS } + +#ifdef CONFIG_X86_64 +ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected GOT/PLT entries detected!") +#else +ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0xc, "Unexpected GOT/PLT entries detected!") +#endif -- 2.25.1 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=-13.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 79FA1C433E0 for ; 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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id b22sm9843692pju.26.2020.07.31.16.08.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 31 Jul 2020 16:08:30 -0700 (PDT) From: Kees Cook To: Thomas Gleixner , Will Deacon Subject: [PATCH v5 01/36] x86/boot/compressed: Move .got.plt entries out of the .got section Date: Fri, 31 Jul 2020 16:07:45 -0700 Message-Id: <20200731230820.1742553-2-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200731230820.1742553-1-keescook@chromium.org> References: <20200731230820.1742553-1-keescook@chromium.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200731_190836_700512_4027242E X-CRM114-Status: GOOD ( 18.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, Kees Cook , Arnd Bergmann , Catalin Marinas , Masahiro Yamada , x86@kernel.org, Nick Desaulniers , Russell King , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Arvind Sankar , Ingo Molnar , James Morse , Sedat Dilek , Nathan Chancellor , Borislav Petkov , Peter Collingbourne , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Ard Biesheuvel The .got.plt section contains the part of the GOT which is used by PLT entries, and which gets updated lazily by the dynamic loader when function calls are dispatched through those PLT entries. On fully linked binaries such as the kernel proper or the decompressor, this never happens, and so in practice, the .got.plt section consists only of the first 3 magic entries that are meant to point at the _DYNAMIC section and at the fixup routine in the loader. However, since we don't use a dynamic loader, those entries are never populated or used. This means that treating those entries like ordinary GOT entries, and updating their values based on the actual placement of the executable in memory is completely pointless, and we can just ignore the .got.plt section entirely, provided that it has no additional entries beyond the first 3 ones. So add an assertion in the linker script to ensure that this assumption holds, and move the contents out of the [_got, _egot) memory range that is modified by the GOT fixup routines. While at it, drop the KEEP(), since it has no effect on the contents of output sections that are created by the linker itself. Signed-off-by: Ard Biesheuvel Signed-off-by: Arvind Sankar Tested-by: Sedat Dilek Tested-by: Nick Desaulniers Reviewed-by: Kees Cook Acked-by: Arvind Sankar Link: https://lore.kernel.org/r/20200523120021.34996-2-ardb@kernel.org Signed-off-by: Kees Cook --- arch/x86/boot/compressed/vmlinux.lds.S | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S index 8f1025d1f681..b17d218ccdf9 100644 --- a/arch/x86/boot/compressed/vmlinux.lds.S +++ b/arch/x86/boot/compressed/vmlinux.lds.S @@ -44,10 +44,13 @@ SECTIONS } .got : { _got = .; - KEEP(*(.got.plt)) KEEP(*(.got)) _egot = .; } + .got.plt : { + *(.got.plt) + } + .data : { _data = . ; *(.data) @@ -77,3 +80,9 @@ SECTIONS DISCARDS } + +#ifdef CONFIG_X86_64 +ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected GOT/PLT entries detected!") +#else +ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0xc, "Unexpected GOT/PLT entries detected!") +#endif -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel