[Devel] [PATCH vz10 5/6] ms/selftests/mm: fix -Warray-bounds warnings in pkey_sighandler_tests

[Konstantin Khorenko]

From: Kevin Brodsky <kevin.brodsky at arm.com>

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 at 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 at arm.com>
Cc: Aruna Ramakrishna <aruna.ramakrishna at oracle.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Dave Hansen <dave.hansen at linux.intel.com>
Cc: Joey Gouly <joey.gouly at arm.com>
Cc: Keith Lucas <keith.lucas at oracle.com>
Cc: Ryan Roberts <ryan.roberts at arm.com>
Cc: Shuah Khan <shuah at kernel.org>
Cc: kernel test robot <lkp at intel.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>

(cherry picked from commit 71384f84cbbe7660023b01c1a0fa9cc7dbc487a7)
Conflict in pkey_sighandler_tests.c: removed unused `int *bad` variable
declaration — our branch already uses hardcoded pkey_reg values instead
of pkey_reg_restrictive_default(), so neither `int *bad` nor `u64 pkey_reg`
are needed.

https://virtuozzo.atlassian.net/browse/VSTOR-127529
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>

Feature: fix selftests
---
 tools/testing/selftests/mm/pkey_sighandler_tests.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/mm/pkey_sighandler_tests.c b/tools/testing/selftests/mm/pkey_sighandler_tests.c
index a8088b645ad6..62f2ab8b440a 100644
--- a/tools/testing/selftests/mm/pkey_sighandler_tests.c
+++ b/tools/testing/selftests/mm/pkey_sighandler_tests.c
@@ -116,7 +116,7 @@ static void *thread_segv_with_pkey0_disabled(void *ptr)
 	__write_pkey_reg(0x55555555);
 
 	/* Segfault (with SEGV_MAPERR) */
-	*(int *) (0x1) = 1;
+	*(volatile int *)NULL = 1;
 	return NULL;
 }
 
@@ -132,7 +132,6 @@ static void *thread_segv_pkuerr_stack(void *ptr)
 static void *thread_segv_maperr_ptr(void *ptr)
 {
 	stack_t *stack = ptr;
-	int *bad = (int *)1;
 
 	/*
 	 * Setup alternate signal stack, which should be pkey_mprotect()ed by
@@ -145,7 +144,7 @@ static void *thread_segv_maperr_ptr(void *ptr)
 	__write_pkey_reg(0x55555551);
 
 	/* Segfault */
-	*bad = 1;
+	*(volatile int *)NULL = 1;
 	syscall_raw(SYS_exit, 0, 0, 0, 0, 0, 0);
 	return NULL;
 }
@@ -184,7 +183,7 @@ 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__);
 }
 
@@ -296,7 +295,7 @@ 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__);
 }
 
-- 
2.47.1