selftests/mm: ensure non-global pkey symbols are marked static

The pkey tests define a whole lot of functions and some global variables. 
A few are truly global (declared in pkey-helpers.h), but the majority are
file-scoped.  Make sure those are labelled static.

Some of the pkey_{access,write}_{allow,deny} helpers are not called, or
only called when building for some architectures.  Mark them
__maybe_unused to suppress compiler warnings.

Link: https://lkml.kernel.org/r/20241209095019.1732120-11-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

@@ -83,6 +83,9 @@ extern void abort_hooks(void);
 #ifndef noinline
 # define noinline __attribute__((noinline))
 #endif
+#ifndef __maybe_unused
+# define __maybe_unused __attribute__((__unused__))
+#endif
 
 int sys_pkey_alloc(unsigned long flags, unsigned long init_val);
 int sys_pkey_free(unsigned long pkey);

tools/testing/selftests/mm/pkey_sighandler_tests.c

@@ -32,9 +32,9 @@
 
 #define STACK_SIZE PTHREAD_STACK_MIN
 
-pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
-pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
-siginfo_t siginfo = {0};
+static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
+static siginfo_t siginfo = {0};
 
 /*
  * We need to use inline assembly instead of glibc's syscall because glibc's