selftests/mm: Add new testcases for pkeys

Add a few new tests to exercise the signal handler flow, especially with
PKEY 0 disabled:

 - Verify that the SIGSEGV handler is invoked when pkey 0 is disabled.

 - Verify that a thread which disables PKEY 0 segfaults with PKUERR when
   accessing the stack.

 - Verify that the SIGSEGV handler that uses an alternate signal stack is
   correctly invoked when the thread disabled PKEY 0

 - Verify that the PKRU value set by the application is correctly restored
   upon return from signal handling.

 - Verify that sigreturn() is able to restore the altstack even if the
   thread had PKEY 0 disabled

[ Aruna: Adapted to upstream ]
[ tglx: Made it actually compile. Restored protection_keys compile. Added
  	useful info to the changelog instead of bare function names. ]

Signed-off-by: Keith Lucas <keith.lucas@oracle.com>
Signed-off-by: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240802061318.2140081-6-aruna.ramakrishna@oracle.com

1 files changed, 0 insertions, 10 deletions

diff --git a/tools/testing/selftests/mm/protection_keys.c b/tools/testing/selftests/mm/protection_keys.c
index eaa6d1fc5328..cc6de1644360 100644
--- a/tools/testing/selftests/mm/protection_keys.c
+++ b/tools/testing/selftests/mm/protection_keys.c
@@ -950,16 +950,6 @@ void close_test_fds(void)
 	nr_test_fds = 0;
 }
 
-#define barrier() __asm__ __volatile__("": : :"memory")
-__attribute__((noinline)) int read_ptr(int *ptr)
-{
-	/*
-	 * Keep GCC from optimizing this away somehow
-	 */
-	barrier();
-	return *ptr;
-}
-
 void test_pkey_alloc_free_attach_pkey0(int *ptr, u16 pkey)
 {
 	int i, err;