selftests/mm: fix -Warray-bounds warnings in pkey_sighandler_tests

GCC doesn't like dereferencing a pointer set to 0x1 (when building
at -O2):

pkey_sighandler_tests.c:166:9: warning: array subscript 0 is outside array bounds of 'int[0]' [-Warray-bounds=]
  166 |         *(int *) (0x1) = 1;
      |         ^~~~~~~~~~~~~~
cc1: note: source object is likely at address zero

Using NULL instead seems to make it happy.  This should make no difference
in practice (SIGSEGV with SEGV_MAPERR will be the outcome regardless), we
just need to update the expected si_addr.

[kevin.brodsky@arm.com: fix clang dereferencing-null issue]
Link: https://lkml.kernel.org/r/20241218153615.2267571-1-kevin.brodsky@arm.com
Link: https://lkml.kernel.org/r/20241209095019.1732120-5-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>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/pkey_sighandler_tests.c b/tools/testing/selftests/mm/pkey_sighandler_tests.c
index c593a42..c6c020a 100644 (file)
--- a/tools/testing/selftests/mm/pkey_sighandler_tests.c
+++ b/tools/testing/selftests/mm/pkey_sighandler_tests.c
@@ -163,7 +163,7 @@ static void *thread_segv_with_pkey0_disabled(void *ptr)
        __write_pkey_reg(pkey_reg_restrictive_default());
 
        /* Segfault (with SEGV_MAPERR) */
-       *(int *) (0x1) = 1;
+       *(volatile int *)NULL = 1;
        return NULL;
 }
 
@@ -179,7 +179,6 @@ static void *thread_segv_pkuerr_stack(void *ptr)
 static void *thread_segv_maperr_ptr(void *ptr)
 {
        stack_t *stack = ptr;
-       int *bad = (int *)1;
        u64 pkey_reg;
 
        /*
@@ -195,7 +194,7 @@ static void *thread_segv_maperr_ptr(void *ptr)
        __write_pkey_reg(pkey_reg);
 
        /* Segfault */
-       *bad = 1;
+       *(volatile int *)NULL = 1;
        syscall_raw(SYS_exit, 0, 0, 0, 0, 0, 0);
        return NULL;
 }
@@ -234,7 +233,7 @@ static void test_sigsegv_handler_with_pkey0_disabled(void)
 
        ksft_test_result(siginfo.si_signo == SIGSEGV &&
                         siginfo.si_code == SEGV_MAPERR &&
-                        siginfo.si_addr == (void *)1,
+                        siginfo.si_addr == NULL,
                         "%s\n", __func__);
 }
 
@@ -349,7 +348,7 @@ static void test_sigsegv_handler_with_different_pkey_for_stack(void)
 
        ksft_test_result(siginfo.si_signo == SIGSEGV &&
                         siginfo.si_code == SEGV_MAPERR &&
-                        siginfo.si_addr == (void *)1,
+                        siginfo.si_addr == NULL,
                         "%s\n", __func__);
 }