[PATCH 7/9] x86, pkeys, selftests: factor out "instruction page"

[Dave Hansen]

From: Dave Hansen <dave.han...@linux.intel.com>

We currently have an execute-only test, but it is for
the explicit mprotect_pkey() interface.  We will soon
add a test for the implicit mprotect(PROT_EXEC)
enterface.  We need this code in both tests.

Signed-off-by: Dave Hansen <dave.han...@linux.intel.com>
Cc: Ram Pai <linux...@us.ibm.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Dave Hansen <dave.han...@intel.com>
Cc: Michael Ellermen <m...@ellerman.id.au>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Shuah Khan <sh...@kernel.org>
---

 b/tools/testing/selftests/x86/protection_keys.c |   21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff -puN 
tools/testing/selftests/x86/protection_keys.c~pkeys-selftests-get_pointer_to_instructions
 tools/testing/selftests/x86/protection_keys.c
--- 
a/tools/testing/selftests/x86/protection_keys.c~pkeys-selftests-get_pointer_to_instructions
 2018-03-26 10:22:37.012170189 -0700
+++ b/tools/testing/selftests/x86/protection_keys.c     2018-03-26 
10:22:37.015170189 -0700
@@ -1277,12 +1277,9 @@ void test_ptrace_of_child(int *ptr, u16
        free(plain_ptr_unaligned);
 }
 
-void test_executing_on_unreadable_memory(int *ptr, u16 pkey)
+void *get_pointer_to_instructions(void)
 {
        void *p1;
-       int scratch;
-       int ptr_contents;
-       int ret;
 
        p1 = ALIGN_PTR_UP(&lots_o_noops_around_write, PAGE_SIZE);
        dprintf3("&lots_o_noops: %p\n", &lots_o_noops_around_write);
@@ -1292,7 +1289,23 @@ void test_executing_on_unreadable_memory
        /* Point 'p1' at the *second* page of the function: */
        p1 += PAGE_SIZE;
 
+       /*
+        * Try to ensure we fault this in on next touch to ensure
+        * we get an instruction fault as opposed to a data one
+        */
        madvise(p1, PAGE_SIZE, MADV_DONTNEED);
+
+       return p1;
+}
+
+void test_executing_on_unreadable_memory(int *ptr, u16 pkey)
+{
+       void *p1;
+       int scratch;
+       int ptr_contents;
+       int ret;
+
+       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);
_