x86/pkeys/selftests: Add a test for pkey 0

Protection key 0 is the default key for all memory and will
not normally come back from pkey_alloc().  But, you might
still want pass it to mprotect_pkey().

This check ensures that you can use pkey 0.

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/20180509171356.9E40B254@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/tools/testing/selftests/x86/protection_keys.c b/tools/testing/selftests/x86/protection_keys.c
index 986ed38a2b25..460b4bdf4c1e 100644
--- a/tools/testing/selftests/x86/protection_keys.c
+++ b/tools/testing/selftests/x86/protection_keys.c
@@ -1184,6 +1184,35 @@ void test_pkey_alloc_exhaust(int *ptr, u16 pkey)
         }
 }
 
+/*
+ * pkey 0 is special.  It is allocated by default, so you do not
+ * have to call pkey_alloc() to use it first.  Make sure that it
+ * is usable.
+ */
+void test_mprotect_with_pkey_0(int *ptr, u16 pkey)
+{
+        long size;
+        int prot;
+
+        assert(pkey_last_malloc_record);
+        size = pkey_last_malloc_record->size;
+        /*
+         * This is a bit of a hack.  But mprotect() requires
+         * huge-page-aligned sizes when operating on hugetlbfs.
+         * So, make sure that we use something that's a multiple
+         * of a huge page when we can.
+         */
+        if (size >= HPAGE_SIZE)
+                size = HPAGE_SIZE;
+        prot = pkey_last_malloc_record->prot;
+
+        /* Use pkey 0 */
+        mprotect_pkey(ptr, size, prot, 0);
+
+        /* Make sure that we can set it back to the original pkey. */
+        mprotect_pkey(ptr, size, prot, pkey);
+}
+
 void test_ptrace_of_child(int *ptr, u16 pkey)
 {
         __attribute__((__unused__)) int peek_result;
@@ -1378,6 +1407,7 @@ void (*pkey_tests[])(int *ptr, u16 pkey) = {
         test_kernel_gup_write_to_write_disabled_region,
         test_executing_on_unreadable_memory,
         test_implicit_mprotect_exec_only_memory,
+        test_mprotect_with_pkey_0,
         test_ptrace_of_child,
         test_pkey_syscalls_on_non_allocated_pkey,
         test_pkey_syscalls_bad_args,