selftests/mm: remove empty pkey helper definition

Some of the functions declared in pkey-helpers.h are actually defined in
protections_keys.c, meaning they can only be called from
protections_keys.c. This is less than ideal, but it is hard to avoid as
these helpers are themselves called from inline functions in
pkey-<arch>.h. Let's at least add a comment clarifying that. We can also
remove the empty definition in pkey_sighandler_tests.c:
expected_pkey_fault() is not meant to be called from there.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kevin Brodsky <[e-mail]>
Cc: Aruna Ramakrishna <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Joey Gouly <[e-mail]>
Cc: Keith Lucas <[e-mail]>
Cc: Ryan Roberts <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

tools/testing/selftests/mm/pkey-helpers.h

···
 # define noinline __attribute__((noinline))
 #endif
 
-noinline int read_ptr(int *ptr);
-void expected_pkey_fault(int pkey);
 int sys_pkey_alloc(unsigned long flags, unsigned long init_val);
 int sys_pkey_free(unsigned long pkey);
+
+/* For functions called from protection_keys.c only */
+noinline int read_ptr(int *ptr);
+void expected_pkey_fault(int pkey);
 int mprotect_pkey(void *ptr, size_t size, unsigned long orig_prot,
 		unsigned long pkey);
 void record_pkey_malloc(void *ptr, long size, int prot);

tools/testing/selftests/mm/pkey_sighandler_tests.c

···
 
 #define STACK_SIZE PTHREAD_STACK_MIN
 
-void expected_pkey_fault(int pkey) {}
-
 pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
 siginfo_t siginfo = {0};