m68k: Enforce 4-byte alignment on internal locks (BZ #29537)

A new internal definition, __LIBC_LOCK_ALIGNMENT, is used to force
the 4-byte alignment only for m68k, other architecture keep the
natural alignment of the type used internally (and hppa does not
require 16-byte alignment for kernel-assisted CAS).

Reviewed-by: Florian Weimer <fweimer@redhat.com>

4 files changed, 59 insertions, 2 deletions

diff --git a/sysdeps/generic/libc-lock-arch.h b/sysdeps/generic/libc-lock-arch.h
new file mode 100644
index 0000000000..4713b30a8a
--- /dev/null
+++ b/sysdeps/generic/libc-lock-arch.h
@@ -0,0 +1,25 @@
+/* Private libc-internal arch-specific definitions.  Generic version.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _LIBC_LOCK_ARCH_H
+#define _LIBC_LOCK_ARCH_H
+
+/* The default definition uses the natural alignment from the lock type.  */
+#define __LIBC_LOCK_ALIGNMENT
+
+#endif
diff --git a/sysdeps/nptl/libc-lock.h b/sysdeps/nptl/libc-lock.h
index 5af476c48b..63b3f3d75c 100644
--- a/sysdeps/nptl/libc-lock.h
+++ b/sysdeps/nptl/libc-lock.h
@@ -22,6 +22,7 @@
 #include <pthread.h>
 #define __need_NULL
 #include <stddef.h>
+#include <libc-lock-arch.h>
 
 
 /* Mutex type.  */
@@ -29,7 +30,12 @@
 # if (!IS_IN (libc) && !IS_IN (libpthread)) || !defined _LIBC
 typedef struct { pthread_mutex_t mutex; } __libc_lock_recursive_t;
 # else
-typedef struct { int lock; int cnt; void *owner; } __libc_lock_recursive_t;
+typedef struct
+{
+  int lock __LIBC_LOCK_ALIGNMENT;
+  int cnt;
+  void *owner;
+} __libc_lock_recursive_t;
 # endif
 #else
 typedef struct __libc_lock_recursive_opaque__ __libc_lock_recursive_t;
diff --git a/sysdeps/nptl/libc-lockP.h b/sysdeps/nptl/libc-lockP.h
index d3a6837fd2..425f514c5c 100644
--- a/sysdeps/nptl/libc-lockP.h
+++ b/sysdeps/nptl/libc-lockP.h
@@ -32,9 +32,10 @@
    ld.so might be used on old kernels with a different libc.so.  */
 #include <lowlevellock.h>
 #include <tls.h>
+#include <libc-lock-arch.h>
 
 /* Mutex type.  */
-typedef int __libc_lock_t;
+typedef int __libc_lock_t __LIBC_LOCK_ALIGNMENT;
 typedef struct { pthread_mutex_t mutex; } __rtld_lock_recursive_t;
 typedef pthread_rwlock_t __libc_rwlock_t;
 
diff --git a/sysdeps/unix/sysv/linux/m68k/libc-lock-arch.h b/sysdeps/unix/sysv/linux/m68k/libc-lock-arch.h
new file mode 100644
index 0000000000..1844bbaf6f
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/m68k/libc-lock-arch.h
@@ -0,0 +1,25 @@
+/* Private libc-internal arch-specific definitions.  m68k version.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _LIBC_LOCK_ARCH_H
+#define _LIBC_LOCK_ARCH_H
+
+/* Linux enforces 4-bytes alignment on futex inputs.  */
+#define __LIBC_LOCK_ALIGNMENT __attribute__ ((__aligned__ (4)))
+
+#endif