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

[Dave Hansen]

From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

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.hansen@xxxxxxxxxxxxxxx>
Cc: Ram Pai <linuxram@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Michael Ellermen <mpe@xxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
---

 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);
_