x86/pkeys/selftests: Add PROT_EXEC test

Under the covers, implement executable-only memory with
protection keys when userspace calls mprotect(PROT_EXEC).

But, we did not have a selftest for that.  Now we do.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellermen <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180509171348.9EEE4BEF@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/tools/testing/selftests/x86/protection_keys.c b/tools/testing/selftests/x86/protection_keys.c
index 083ebd51b44e..8cb4fe58f381 100644
--- a/tools/testing/selftests/x86/protection_keys.c
+++ b/tools/testing/selftests/x86/protection_keys.c
@@ -1303,6 +1303,49 @@ void test_executing_on_unreadable_memory(int *ptr, u16 pkey)
         expected_pk_fault(pkey);
 }
 
+void test_implicit_mprotect_exec_only_memory(int *ptr, u16 pkey)
+{
+        void *p1;
+        int scratch;
+        int ptr_contents;
+        int ret;
+
+        dprintf1("%s() start\n", __func__);
+
+        p1 = get_pointer_to_instructions();
+        lots_o_noops_around_write(&scratch);
+        ptr_contents = read_ptr(p1);
+        dprintf2("ptr (%p) contents@%d: %x\n", p1, __LINE__, ptr_contents);
+
+        /* Use a *normal* mprotect(), not mprotect_pkey(): */
+        ret = mprotect(p1, PAGE_SIZE, PROT_EXEC);
+        pkey_assert(!ret);
+
+        dprintf2("pkru: %x\n", rdpkru());
+
+        /* Make sure this is an *instruction* fault */
+        madvise(p1, PAGE_SIZE, MADV_DONTNEED);
+        lots_o_noops_around_write(&scratch);
+        do_not_expect_pk_fault("executing on PROT_EXEC memory");
+        ptr_contents = read_ptr(p1);
+        dprintf2("ptr (%p) contents@%d: %x\n", p1, __LINE__, ptr_contents);
+        expected_pk_fault(UNKNOWN_PKEY);
+
+        /*
+         * Put the memory back to non-PROT_EXEC.  Should clear the
+         * exec-only pkey off the VMA and allow it to be readable
+         * again.  Go to PROT_NONE first to check for a kernel bug
+         * that did not clear the pkey when doing PROT_NONE.
+         */
+        ret = mprotect(p1, PAGE_SIZE, PROT_NONE);
+        pkey_assert(!ret);
+
+        ret = mprotect(p1, PAGE_SIZE, PROT_READ|PROT_EXEC);
+        pkey_assert(!ret);
+        ptr_contents = read_ptr(p1);
+        do_not_expect_pk_fault("plain read on recently PROT_EXEC area");
+}
+
 void test_mprotect_pkey_on_unsupported_cpu(int *ptr, u16 pkey)
 {
         int size = PAGE_SIZE;
@@ -1327,6 +1370,7 @@ void (*pkey_tests[])(int *ptr, u16 pkey) = {
         test_kernel_gup_of_access_disabled_region,
         test_kernel_gup_write_to_write_disabled_region,
         test_executing_on_unreadable_memory,
+        test_implicit_mprotect_exec_only_memory,
         test_ptrace_of_child,
         test_pkey_syscalls_on_non_allocated_pkey,
         test_pkey_syscalls_bad_args,