From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-x544.google.com ([2607:f8b0:4864:20::544]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1ihMzU-0004MX-1i for linux-um@lists.infradead.org; Wed, 18 Dec 2019 00:15:01 +0000 Received: by mail-pg1-x544.google.com with SMTP id 6so231755pgk.0 for ; Tue, 17 Dec 2019 16:14:59 -0800 (PST) Date: Tue, 17 Dec 2019 16:14:56 -0800 From: Kees Cook Subject: Re: [PATCH v1] lkdtm/bugs: fix build error in lkdtm_UNSET_SMEP Message-ID: <201912171613.454319D@keescook> References: <20191213003522.66450-1-brendanhiggins@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191213003522.66450-1-brendanhiggins@google.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: Brendan Higgins Cc: arnd@arndb.de, richard@nod.at, jdike@addtoit.com, linux-um@lists.infradead.org, linux-kernel@vger.kernel.org, davidgow@google.com, gregkh@linuxfoundation.org, anton.ivanov@cambridgegreys.com T24gVGh1LCBEZWMgMTIsIDIwMTkgYXQgMDQ6MzU6MjJQTSAtMDgwMCwgQnJlbmRhbiBIaWdnaW5z IHdyb3RlOgo+IFdoZW4gYnVpbGRpbmcgQVJDSD11bSB3aXRoIENPTkZJR19VTUxfWDg2PXkgYW5k IENPTkZJR182NEJJVD15IHdlIGdldAo+IHRoZSBidWlsZCBlcnJvcnM6Cj4gCj4gZHJpdmVycy9t aXNjL2xrZHRtL2J1Z3MuYzogSW4gZnVuY3Rpb24g4oCYbGtkdG1fVU5TRVRfU01FUOKAmToKPiBk cml2ZXJzL21pc2MvbGtkdG0vYnVncy5jOjI4ODo4OiBlcnJvcjogaW1wbGljaXQgZGVjbGFyYXRp b24gb2YgZnVuY3Rpb24g4oCYbmF0aXZlX3JlYWRfY3I04oCZIFstV2Vycm9yPWltcGxpY2l0LWZ1 bmN0aW9uLWRlY2xhcmF0aW9uXQo+ICAgY3I0ID0gbmF0aXZlX3JlYWRfY3I0KCk7Cj4gICAgICAg ICBefn5+fn5+fn5+fn5+fn4KPiBkcml2ZXJzL21pc2MvbGtkdG0vYnVncy5jOjI5MDoxMzogZXJy b3I6IOKAmFg4Nl9DUjRfU01FUOKAmSB1bmRlY2xhcmVkIChmaXJzdCB1c2UgaW4gdGhpcyBmdW5j dGlvbik7IGRpZCB5b3UgbWVhbiDigJhYODZfRkVBVFVSRV9TTUVQ4oCZPwo+ICAgaWYgKChjcjQg 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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id g10sm157229pgh.35.2019.12.17.16.14.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Dec 2019 16:14:57 -0800 (PST) Date: Tue, 17 Dec 2019 16:14:56 -0800 From: Kees Cook To: Brendan Higgins Cc: jdike@addtoit.com, richard@nod.at, anton.ivanov@cambridgegreys.com, linux-um@lists.infradead.org, linux-kernel@vger.kernel.org, davidgow@google.com, arnd@arndb.de, gregkh@linuxfoundation.org Subject: Re: [PATCH v1] lkdtm/bugs: fix build error in lkdtm_UNSET_SMEP Message-ID: <201912171613.454319D@keescook> References: <20191213003522.66450-1-brendanhiggins@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20191213003522.66450-1-brendanhiggins@google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 12, 2019 at 04:35:22PM -0800, Brendan Higgins wrote: > When building ARCH=um with CONFIG_UML_X86=y and CONFIG_64BIT=y we get > the build errors: > > drivers/misc/lkdtm/bugs.c: In function ‘lkdtm_UNSET_SMEP’: > drivers/misc/lkdtm/bugs.c:288:8: error: implicit declaration of function ‘native_read_cr4’ [-Werror=implicit-function-declaration] > cr4 = native_read_cr4(); > ^~~~~~~~~~~~~~~ > drivers/misc/lkdtm/bugs.c:290:13: error: ‘X86_CR4_SMEP’ undeclared (first use in this function); did you mean ‘X86_FEATURE_SMEP’? > if ((cr4 & X86_CR4_SMEP) != X86_CR4_SMEP) { > ^~~~~~~~~~~~ > X86_FEATURE_SMEP > drivers/misc/lkdtm/bugs.c:290:13: note: each undeclared identifier is reported only once for each function it appears in > drivers/misc/lkdtm/bugs.c:297:2: error: implicit declaration of function ‘native_write_cr4’; did you mean ‘direct_write_cr4’? [-Werror=implicit-function-declaration] > native_write_cr4(cr4); > ^~~~~~~~~~~~~~~~ > direct_write_cr4 > > So specify that this block of code should only build when > CONFIG_X86_64=y *AND* CONFIG_UML is unset. > > Signed-off-by: Brendan Higgins Thanks for catching this! Is a similar marking needed for the recently added lkdtm_DOUBLE_FAULT() when using UML on 32-bit? Acked-by: Kees Cook -Kees > --- > > This patch is part of my larger effort to get allyesconfig closer to > working for ARCH=um. For more information about that, checkout the cover > letter for a related patchset here: > > https://lore.kernel.org/lkml/20191211192742.95699-1-brendanhiggins@google.com/ > > --- > drivers/misc/lkdtm/bugs.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c > index a4fdad04809a9..6c1aab177fced 100644 > --- a/drivers/misc/lkdtm/bugs.c > +++ b/drivers/misc/lkdtm/bugs.c > @@ -278,7 +278,7 @@ void lkdtm_STACK_GUARD_PAGE_TRAILING(void) > > void lkdtm_UNSET_SMEP(void) > { > -#ifdef CONFIG_X86_64 > +#if IS_ENABLED(CONFIG_X86_64) && !IS_ENABLED(CONFIG_UML) > #define MOV_CR4_DEPTH 64 > void (*direct_write_cr4)(unsigned long val); > unsigned char *insn; > -- > 2.24.1.735.g03f4e72817-goog > -- Kees Cook