[PATCH AUTOSEL 5.4 064/107] lkdtm/bugs: fix build error in lkdtm_UNSET_SMEP

[Sasha Levin]

From: Brendan Higgins <brendanhiggins@xxxxxxxxxx>

[ Upstream commit 0e31e3573f0cd94d7b821117db854187ffc85765 ]

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 âlkdtm_UNSET_SMEPâ:
drivers/misc/lkdtm/bugs.c:288:8: error: implicit declaration of function ânative_read_cr4â [-Werror=implicit-function-declaration]
  cr4 = native_read_cr4();
        ^~~~~~~~~~~~~~~
drivers/misc/lkdtm/bugs.c:290:13: error: âX86_CR4_SMEPâ undeclared (first use in this function); did you mean âX86_FEATURE_SMEPâ?
  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 ânative_write_cr4â; did you mean âdirect_write_cr4â? [-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 <brendanhiggins@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20191213003522.66450-1-brendanhiggins@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 7284a22b1a09e..4d5a512769e99 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -274,7 +274,7 @@ 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;
-- 
2.20.1