linux-kernel - [PATCH AUTOSEL 5.4 064/107] lkdtm/bugs: fix build error in lkdtm_UNSET

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Date:   Fri, 24 Jan 2020 09:17:34 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.4 064/107] lkdtm/bugs: fix build error in lkdtm_UNSET_SMEP

From: Brendan Higgins <brendanhiggins@...gle.com>

[ 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 ‘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 <brendanhiggins@...gle.com>
Acked-by: Kees Cook <keescook@...omium.org>
Link: https://lore.kernel.org/r/20191213003522.66450-1-brendanhiggins@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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