linux-kernel - [tip: locking/futex] selftests/futex: Fix futex

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Message-ID: <175673688994.1920.3268727903650888597.tip-bot2@tip-bot2>
Date: Mon, 01 Sep 2025 14:28:09 -0000
From: "tip-bot2 for Dan Carpenter" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Dan Carpenter <dan.carpenter@...aro.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 "Borislav Petkov (AMD)" <bp@...en8.de>, andrealmeid@...lia.com,
 Anders Roxell <anders.roxell@...aro.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: locking/futex] selftests/futex: Fix futex_wait() for 32bit ARM

The following commit has been merged into the locking/futex branch of tip:

Commit-ID:     237bfb76c90b184f57bb18fe35ff366c19393dc8
Gitweb:        https://git.kernel.org/tip/237bfb76c90b184f57bb18fe35ff366c19393dc8
Author:        Dan Carpenter <dan.carpenter@...aro.org>
AuthorDate:    Wed, 27 Aug 2025 15:00:11 +02:00
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Mon, 01 Sep 2025 16:26:55 +02:00

selftests/futex: Fix futex_wait() for 32bit ARM

On 32bit ARM systems gcc-12 will use 32bit timestamps while gcc-13 and later
will use 64bit timestamps.  The problem is that SYS_futex will continue
pointing at the 32bit system call.  This makes the futex_wait test fail like
this:

  waiter failed errno 110
  not ok 1 futex_wake private returned: 0 Success
  waiter failed errno 110
  not ok 2 futex_wake shared (page anon) returned: 0 Success
  waiter failed errno 110
  not ok 3 futex_wake shared (file backed) returned: 0 Success

Instead of compiling differently depending on the gcc version, use the
-D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64 options to ensure that 64bit timestamps
are used.  Then use ifdefs to make SYS_futex point to the 64bit system call.

Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: André Almeida <andrealmeid@...lia.com>
Tested-by: Anders Roxell <anders.roxell@...aro.org>
Link: https://lore.kernel.org/20250827130011.677600-6-bigeasy@linutronix.de
---
 tools/testing/selftests/futex/functional/Makefile |  2 +-
 tools/testing/selftests/futex/include/futextest.h | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile
index 8cfb87f..ddfa61d 100644
--- a/tools/testing/selftests/futex/functional/Makefile
+++ b/tools/testing/selftests/futex/functional/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 INCLUDES := -I../include -I../../ $(KHDR_INCLUDES)
-CFLAGS := $(CFLAGS) -g -O2 -Wall -pthread $(INCLUDES) $(KHDR_INCLUDES)
+CFLAGS := $(CFLAGS) -g -O2 -Wall -pthread -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64 $(INCLUDES) $(KHDR_INCLUDES)
 LDLIBS := -lpthread -lrt -lnuma
 
 LOCAL_HDRS := \
diff --git a/tools/testing/selftests/futex/include/futextest.h b/tools/testing/selftests/futex/include/futextest.h
index 7a5fd1d..3d48e97 100644
--- a/tools/testing/selftests/futex/include/futextest.h
+++ b/tools/testing/selftests/futex/include/futextest.h
@@ -58,6 +58,17 @@ typedef volatile u_int32_t futex_t;
 #define SYS_futex SYS_futex_time64
 #endif
 
+/*
+ * On 32bit systems if we use "-D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64" or if
+ * we are using a newer compiler then the size of the timestamps will be 64bit,
+ * however, the SYS_futex will still point to the 32bit futex system call.
+ */
+#if __SIZEOF_POINTER__ == 4 && defined(SYS_futex_time64) && \
+	defined(_TIME_BITS) && _TIME_BITS == 64
+# undef SYS_futex
+# define SYS_futex SYS_futex_time64
+#endif
+
 /**
  * futex() - SYS_futex syscall wrapper
  * @uaddr:	address of first futex