[PATCH kvm-unit-tests v4] Check SMEP when cr0.wp=0

Yang, Wei
2011-07-06T03:01:54Z

This patch adds SMEP to all test cases and checks SMEP when cr0.wp=0.

changes since v3:
Add Reviewed-by
changes since v2:
Recover U/S bit after turning off SMEP and correct the title
changes since v1:
Add SMEP to all test cases and verify it before setting cr4

Signed-off-by: Yang, Wei <wei.y.yang@intel.com>
Signed-off-by: Shan, Haitao <haitao.shan@intel.com>
Signed-off-by: Li, Xin <xin.li@intel.com>
Reviewed-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>

---
x86/access.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
x86/cstart64.S | 1 +
2 files changed, 110 insertions(+), 3 deletions(-)

diff --git a/x86/access.c b/x86/access.c
index 7c8b9a5..23a5995 100644
--- a/x86/access.c
+++ b/x86/access.c
@@ -27,6 +27,7 @@ typedef unsigned long pt_element_t;
#define PT_NX_MASK ((pt_element_t)1 << 63)

#define CR0_WP_MASK (1UL << 16)
+#define CR4_SMEP_MASK (1UL << 20)

#define PFERR_PRESENT_MASK (1U << 0)
#define PFERR_WRITE_MASK (1U << 1)
@@ -70,6 +71,7 @@ enum {

AC_CPU_EFER_NX,
AC_CPU_CR0_WP,
+ AC_CPU_CR4_SMEP,

NR_AC_FLAGS
};
@@ -96,6 +98,7 @@ const char *ac_names[] = {
[AC_ACCESS_TWICE] = "twice",
[AC_CPU_EFER_NX] = "efer.nx",
[AC_CPU_CR0_WP] = "cr0.wp",
+ [AC_CPU_CR4_SMEP] = "cr4.smep",
};

static inline void *va(pt_element_t phys)
@@ -130,6 +133,14 @@ typedef struct {

static void ac_test_show(ac_test_t *at);

+int write_cr4_checking(unsigned long val)
+{
+ asm volatile(ASM_TRY("1f")
+ "mov %0,%%cr4\n\t"
+ "1:": : "r" (val));
+ return exception_vector();
+}
+
void set_cr0_wp(int wp)
{
unsigned long cr0 = read_cr0();
@@ -140,6 +151,16 @@ void set_cr0_wp(int wp)
write_cr0(cr0);
}

+void set_cr4_smep(int smep)
+{
+ unsigned long cr4 = read_cr4();
+
+ cr4 &= ~CR4_SMEP_MASK;
+ if (smep)
+ cr4 |= CR4_SMEP_MASK;
+ write_cr4(cr4);
+}
+
void set_efer_nx(int nx)
{
unsigned long long efer;
@@ -187,7 +208,12 @@ int ac_test_bump_one(ac_test_t *at)

_Bool ac_test_legal(ac_test_t *at)
{
- if (at->flags[AC_ACCESS_FETCH] && at->flags[AC_ACCESS_WRITE])
+ /*
+ * Since we convert current page to kernel page when cr4.smep=1,
+ * we can't switch to user mode.
+ */
+ if ((at->flags[AC_ACCESS_FETCH] && at->flags[AC_ACCESS_WRITE]) ||
+ (at->flags[AC_ACCESS_USER] && at->flags[AC_CPU_CR4_SMEP]))
return false;
return true;
}
@@ -287,6 +313,9 @@ void ac_set_expected_status(ac_test_t *at)
if (at->flags[AC_PDE_PSE]) {
if (at->flags[AC_ACCESS_WRITE] && !at->expected_fault)
at->expected_pde |= PT_DIRTY_MASK;
+ if (at->flags[AC_ACCESS_FETCH] && at->flags[AC_PDE_USER]
+ && at->flags[AC_CPU_CR4_SMEP])
+ at->expected_fault = 1;
goto no_pte;
}

@@ -306,7 +335,11 @@ void ac_set_expected_status(ac_test_t *at)
&& (at->flags[AC_CPU_CR0_WP] || at->flags[AC_ACCESS_USER]))
at->expected_fault = 1;

- if (at->flags[AC_ACCESS_FETCH] && at->flags[AC_PTE_NX])
+ if (at->flags[AC_ACCESS_FETCH]
+ && (at->flags[AC_PTE_NX]
+ || (at->flags[AC_CPU_CR4_SMEP]
+ && at->flags[AC_PDE_USER]
+ && at->flags[AC_PTE_USER])))
at->expected_fault = 1;

if (at->expected_fault)
@@ -320,7 +353,7 @@ no_pte:
fault:
if (!at->expected_fault)
at->ignore_pde = 0;
- if (!at->flags[AC_CPU_EFER_NX])
+ if (!at->flags[AC_CPU_EFER_NX] && !at->flags[AC_CPU_CR4_SMEP])
at->expected_error &= ~PFERR_FETCH_MASK;
}

@@ -469,6 +502,14 @@ int ac_test_do_access(ac_test_t *at)
unsigned r = unique;
set_cr0_wp(at->flags[AC_CPU_CR0_WP]);
set_efer_nx(at->flags[AC_CPU_EFER_NX]);
+ if (at->flags[AC_CPU_CR4_SMEP] && !(cpuid(7).b & (1 << 7))) {
+ unsigned long cr4 = read_cr4();
+ if (write_cr4_checking(cr4 | CR4_SMEP_MASK) == GP_VECTOR)
+ goto done;
+ printf("Set SMEP in CR4 - expect #GP: FAIL!\n");
+ return 0;
+ }
+ set_cr4_smep(at->flags[AC_CPU_CR4_SMEP]);

if (at->flags[AC_ACCESS_TWICE]) {
asm volatile (
@@ -544,6 +585,7 @@ int ac_test_do_access(ac_test_t *at)
!pt_match(*at->pdep, at->expected_pde, at->ignore_pde),
"pde %x expected %x", *at->pdep, at->expected_pde);

+done:
if (success && verbose) {
printf("PASS\n");
}
@@ -645,6 +687,58 @@ err:
return 0;
}

+static int check_smep_andnot_wp(ac_pool_t *pool)
+{
+ ac_test_t at1;
+ int err_prepare_andnot_wp, err_smep_andnot_wp;
+ extern u64 ptl2[];
+
+ ac_test_init(&at1, (void *)(0x123406001000));
+
+ at1.flags[AC_PDE_PRESENT] = 1;
+ at1.flags[AC_PTE_PRESENT] = 1;
+ at1.flags[AC_PDE_USER] = 1;
+ at1.flags[AC_PTE_USER] = 1;
+ at1.flags[AC_PDE_ACCESSED] = 1;
+ at1.flags[AC_PTE_ACCESSED] = 1;
+ at1.flags[AC_CPU_CR4_SMEP] = 1;
+ at1.flags[AC_CPU_CR0_WP] = 0;
+ at1.flags[AC_ACCESS_WRITE] = 1;
+ ac_test_setup_pte(&at1, pool);
+ ptl2[2] -= 0x4;
+
+ /*
+ * Here we write the ro user page when
+ * cr0.wp=0, then we execute it and SMEP
+ * fault should happen.
+ */
+ err_prepare_andnot_wp = ac_test_do_access(&at1);
+ if (!err_prepare_andnot_wp) {
+ printf("%s: SMEP prepare fail\n", __FUNCTION__);
+ goto clean_up;
+ }
+
+ at1.flags[AC_ACCESS_WRITE] = 0;
+ at1.flags[AC_ACCESS_FETCH] = 1;
+ ac_set_expected_status(&at1);
+ err_smep_andnot_wp = ac_test_do_access(&at1);
+
+clean_up:
+ set_cr4_smep(0);
+ ptl2[2] += 0x4;
+
+ if (!err_prepare_andnot_wp)
+ goto err;
+ if (!err_smep_andnot_wp) {
+ printf("%s: check SMEP without wp fail\n", __FUNCTION__);
+ goto err;
+ }
+ return 1;
+
+err:
+ return 0;
+}
+
int ac_test_exec(ac_test_t *at, ac_pool_t *pool)
{
int r;
@@ -662,6 +756,7 @@ const ac_test_fn ac_test_cases[] =
{
corrupt_hugepage_triger,
check_pfec_on_prefetch_pte,
+ check_smep_andnot_wp
};

int ac_test_run(void)
@@ -669,16 +764,27 @@ int ac_test_run(void)
ac_test_t at;
ac_pool_t pool;
int i, tests, successes;
+ extern u64 ptl2[];

printf("run\n");
tests = successes = 0;
ac_env_int(&pool);
ac_test_init(&at, (void *)(0x123400000000 + 16 * smp_id()));
do {
+ if (at.flags[AC_CPU_CR4_SMEP] && (ptl2[2] & 0x4))
+ ptl2[2] -= 0x4;
+ if (!at.flags[AC_CPU_CR4_SMEP] && !(ptl2[2] & 0x4)) {
+ set_cr4_smep(0);
+ ptl2[2] += 0x4;
+ }
+
++tests;
successes += ac_test_exec(&at, &pool);
} while (ac_test_bump(&at));

+ set_cr4_smep(0);
+ ptl2[2] += 0x4;
+
for (i = 0; i < ARRAY_SIZE(ac_test_cases); i++) {
++tests;
successes += ac_test_cases[i](&pool);
diff --git a/x86/cstart64.S b/x86/cstart64.S
index 71014d8..24df5f8 100644
--- a/x86/cstart64.S
+++ b/x86/cstart64.S
@@ -21,6 +21,7 @@ ring0stacktop:
.data

.align 4096
+.globl ptl2
ptl2:
i = 0
.rept 512 * 4
--
1.7.4.1