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    Subject[PATCH AUTOSEL 5.4 064/107] lkdtm/bugs: fix build error in lkdtm_UNSET_SMEP
    Date
    From: Brendan Higgins <brendanhiggins@google.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@google.com>
    Acked-by: Kees Cook <keescook@chromium.org>
    Link: https://lore.kernel.org/r/20191213003522.66450-1-brendanhiggins@google.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.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
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