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/20241209095019.1732120-10-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Keith Lucas <keith.lucas@oracle.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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

@@ -84,10 +84,12 @@ extern void abort_hooks(void);
 # 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

@@ -32,8 +32,6 @@
 
 #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};