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Subject[PATCH 4/4] lkdtm: Make arch-specific tests always available
Date
I'd like arch-specific tests to XFAIL when on a mismatched architecture
so that we can more easily compare test coverage across all systems.
Lacking kernel configs or CPU features count as a FAIL, not an XFAIL.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/misc/lkdtm/bugs.c | 34 ++++++++++++++-----------
drivers/misc/lkdtm/lkdtm.h | 2 --
tools/testing/selftests/lkdtm/tests.txt | 1 +
3 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index e1b43f615549..f3fde0759f2c 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -453,38 +453,42 @@ void lkdtm_DOUBLE_FAULT(void)
#endif
}

-#ifdef CONFIG_ARM64_PTR_AUTH
+#ifdef CONFIG_ARM64
static noinline void change_pac_parameters(void)
{
- /* Reset the keys of current task */
- ptrauth_thread_init_kernel(current);
- ptrauth_thread_switch_kernel(current);
+ if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH)) {
+ /* Reset the keys of current task */
+ ptrauth_thread_init_kernel(current);
+ ptrauth_thread_switch_kernel(current);
+ }
}
+#endif

-#define CORRUPT_PAC_ITERATE 10
noinline void lkdtm_CORRUPT_PAC(void)
{
+#ifdef CONFIG_ARM64
+#define CORRUPT_PAC_ITERATE 10
int i;

+ if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH))
+ pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH\n");
+
if (!system_supports_address_auth()) {
- pr_err("FAIL: arm64 pointer authentication feature not present\n");
+ pr_err("FAIL: CPU lacks pointer authentication feature\n");
return;
}

- pr_info("Change the PAC parameters to force function return failure\n");
+ pr_info("changing PAC parameters to force function return failure...\n");
/*
- * Pac is a hash value computed from input keys, return address and
+ * PAC is a hash value computed from input keys, return address and
* stack pointer. As pac has fewer bits so there is a chance of
* collision, so iterate few times to reduce the collision probability.
*/
for (i = 0; i < CORRUPT_PAC_ITERATE; i++)
change_pac_parameters();

- pr_err("FAIL: %s test failed. Kernel may be unstable from here\n", __func__);
-}
-#else /* !CONFIG_ARM64_PTR_AUTH */
-noinline void lkdtm_CORRUPT_PAC(void)
-{
- pr_err("FAIL: arm64 pointer authentication config disabled\n");
-}
+ pr_err("FAIL: survived PAC changes! Kernel may be unstable from here\n");
+#else
+ pr_err("XFAIL: this test is arm64-only\n");
#endif
+}
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index 601a2156a0d4..8878538b2c13 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -31,9 +31,7 @@ void lkdtm_CORRUPT_USER_DS(void);
void lkdtm_STACK_GUARD_PAGE_LEADING(void);
void lkdtm_STACK_GUARD_PAGE_TRAILING(void);
void lkdtm_UNSET_SMEP(void);
-#ifdef CONFIG_X86_32
void lkdtm_DOUBLE_FAULT(void);
-#endif
void lkdtm_CORRUPT_PAC(void);

/* lkdtm_heap.c */
diff --git a/tools/testing/selftests/lkdtm/tests.txt b/tools/testing/selftests/lkdtm/tests.txt
index 92ca32143ae5..9d266e79c6a2 100644
--- a/tools/testing/selftests/lkdtm/tests.txt
+++ b/tools/testing/selftests/lkdtm/tests.txt
@@ -14,6 +14,7 @@ STACK_GUARD_PAGE_LEADING
STACK_GUARD_PAGE_TRAILING
UNSET_SMEP CR4 bits went missing
DOUBLE_FAULT
+CORRUPT_PAC
UNALIGNED_LOAD_STORE_WRITE
#OVERWRITE_ALLOCATION Corrupts memory on failure
#WRITE_AFTER_FREE Corrupts memory on failure
--
2.25.1
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