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Date:   Thu, 12 Dec 2019 16:35:22 -0800
Message-Id: <20191213003522.66450-1-brendanhiggins@google.com>
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Subject: [PATCH v1] lkdtm/bugs: fix build error in lkdtm_UNSET_SMEP
From:   Brendan Higgins <brendanhiggins@google.com>
To:     keescook@chromium.org
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,
        Brendan Higgins <brendanhiggins@google.com>
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Sender: linux-kernel-owner@vger.kernel.org
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When building ARCH=3Dum with CONFIG_UML_X86=3Dy and CONFIG_64BIT=3Dy we get
the build errors:

drivers/misc/lkdtm/bugs.c: In function =E2=80=98lkdtm_UNSET_SMEP=E2=80=99:
drivers/misc/lkdtm/bugs.c:288:8: error: implicit declaration of function =
=E2=80=98native_read_cr4=E2=80=99 [-Werror=3Dimplicit-function-declaration]
  cr4 =3D native_read_cr4();
        ^~~~~~~~~~~~~~~
drivers/misc/lkdtm/bugs.c:290:13: error: =E2=80=98X86_CR4_SMEP=E2=80=99 und=
eclared (first use in this function); did you mean =E2=80=98X86_FEATURE_SME=
P=E2=80=99?
  if ((cr4 & X86_CR4_SMEP) !=3D X86_CR4_SMEP) {
             ^~~~~~~~~~~~
             X86_FEATURE_SMEP
drivers/misc/lkdtm/bugs.c:290:13: note: each undeclared identifier is repor=
ted only once for each function it appears in
drivers/misc/lkdtm/bugs.c:297:2: error: implicit declaration of function =
=E2=80=98native_write_cr4=E2=80=99; did you mean =E2=80=98direct_write_cr4=
=E2=80=99? [-Werror=3Dimplicit-function-declaration]
  native_write_cr4(cr4);
  ^~~~~~~~~~~~~~~~
  direct_write_cr4

So specify that this block of code should only build when
CONFIG_X86_64=3Dy *AND* CONFIG_UML is unset.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
---

This patch is part of my larger effort to get allyesconfig closer to
working for ARCH=3Dum. For more information about that, checkout the cover
letter for a related patchset here:

https://lore.kernel.org/lkml/20191211192742.95699-1-brendanhiggins@google.c=
om/

---
 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)
=20
 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;
--=20
2.24.1.735.g03f4e72817-goog