libmultipath: avoid -Warray-bounds error in uatomic_xchg()

The use of uatomic_xchg() in alias.c causes a -Warray-bounds error
on distributions using gcc 12, such as Fedora 37. This is a similar
error to 2534c4f ("libmultipath: avoid -Warray-bounds error with gcc
12 and musl libc"). This happens only with liburcu 0.13 and earlier,
and only with certain gcc versions. See liburcu commit 835b9ab
("Fix: x86 and s390 uatomic: __hp() macro warning with gcc 11").

Enhance the fix for 2534c4f by a workaround for uatomic_xchg(), and
introduce the macro URCU_VERSION (originally only used for multipathd)
globally.

Signed-off-by: Martin Wilck <[email protected]>

Makefile.inc

@@ -95,7 +95,7 @@ OPTFLAGS	:= -O2 -g $(STACKPROT) --param=ssp-buffer-size=4
 WARNFLAGS	:= -Werror -Wall -Wextra -Wformat=2 $(WFORMATOVERFLOW) -Werror=implicit-int \
 		  -Werror=implicit-function-declaration -Werror=format-security \
 		  $(WNOCLOBBERED) -Werror=cast-qual $(ERROR_DISCARDED_QUALIFIERS) $(W_URCU_TYPE_LIMITS)
-CPPFLAGS	:= $(FORTIFY_OPT) $(CPPFLAGS) \
+CPPFLAGS	:= $(FORTIFY_OPT) $(CPPFLAGS) $(D_URCU_VERSION) \
 		   -DBIN_DIR=\"$(bindir)\" -DMULTIPATH_DIR=\"$(plugindir)\" \
 		   -DRUNTIME_DIR=\"$(runtimedir)\" -DCONFIG_DIR=\"$(configdir)\" \
 		   -DDEFAULT_CONFIGFILE=\"$(configfile)\" -DSTATE_DIR=\"$(statedir)\" \

create-config.mk

@@ -73,6 +73,10 @@ TEST_URCU_TYPE_LIMITS = $(shell \
 		$(CC) -c -Werror=type-limits -o /dev/null -xc - 2>/dev/null  \
 	|| echo -Wno-type-limits )
 
+URCU_VERSION = $(shell \
+	$(PKG_CONFIG) --modversion liburcu 2>/dev/null | \
+			awk -F. '{ printf("-DURCU_VERSION=0x%06x", 256 * ( 256 * $$1 + $$2) + $$3); }')
+
 DEFINES :=
 
 ifneq ($(call check_func,dm_task_no_flush,$(devmapper_incdir)/libdevmapper.h),0)
@@ -168,6 +172,7 @@ $(TOPDIR)/config.mk:	$(multipathdir)/autoconfig.h
 	@echo creating $@
 	@echo "FPIN_SUPPORT := $(FPIN_SUPPORT)" >$@
 	@echo "FORTIFY_OPT := $(FORTIFY_OPT)" >>$@
+	@echo "D_URCU_VERSION := $(call URCU_VERSION)" >>$@
 	@echo "SYSTEMD := $(SYSTEMD)" >>$@
 	@echo "ANA_SUPPORT := $(ANA_SUPPORT)" >>$@
 	@echo "STACKPROT := $(call TEST_CC_OPTION,-fstack-protector-strong,-fstack-protector)" >>$@

libmultipath/alias.c

@@ -24,6 +24,7 @@
 #include "devmapper.h"
 #include "strbuf.h"
 #include "time-util.h"
+#include "lock.h"
 
 /*
  * significant parts of this file were taken from iscsi-bindings.c of the
@@ -299,7 +300,7 @@ void handle_bindings_file_inotify(const struct inotify_event *event)
 	pthread_mutex_unlock(&timestamp_mutex);
 
 	if (changed) {
-		uatomic_xchg(&bindings_file_changed, 1);
+		uatomic_xchg_int(&bindings_file_changed, 1);
 		condlog(3, "%s: bindings file must be re-read, new timestamp: %ld.%06ld",
 			__func__, (long)ts.tv_sec, (long)ts.tv_nsec / 1000);
 	} else
@@ -773,7 +774,7 @@ static int _read_bindings_file(const struct config *conf, Bindings *bindings,
 	int rc = 0, ret, fd;
 	FILE *file;
 	struct stat st;
-	int has_changed = uatomic_xchg(&bindings_file_changed, 0);
+	int has_changed = uatomic_xchg_int(&bindings_file_changed, 0);
 
 	if (!force) {
 		if (!has_changed) {

libmultipath/lock.h

@@ -13,15 +13,20 @@ struct mutex_lock {
 	int waiters; /* uatomic access only */
 };
 
-#if !defined(__GLIBC__) && defined(__GNUC__) && __GNUC__ == 12
+static inline void init_lock(struct mutex_lock *a)
+{
+	pthread_mutex_init(&a->mutex, NULL);
+	uatomic_set(&a->waiters, 0);
+}
+
+#if defined(__GNUC__) && __GNUC__ == 12 && URCU_VERSION < 0xe00
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Warray-bounds"
 #endif
 
-static inline void init_lock(struct mutex_lock *a)
+static inline int uatomic_xchg_int(int *ptr, int val)
 {
-	pthread_mutex_init(&a->mutex, NULL);
-	uatomic_set(&a->waiters, 0);
+	return uatomic_xchg(ptr, val);
 }
 
 static inline void lock(struct mutex_lock *a)
@@ -31,6 +36,10 @@ static inline void lock(struct mutex_lock *a)
 	uatomic_dec(&a->waiters);
 }
 
+#if defined(__GNUC__) && __GNUC__ == 12 && URCU_VERSION < 0xe00
+#pragma GCC diagnostic pop
+#endif
+
 static inline int trylock(struct mutex_lock *a)
 {
 	return pthread_mutex_trylock(&a->mutex);
@@ -51,10 +60,6 @@ static inline bool lock_has_waiters(struct mutex_lock *a)
 	return (uatomic_read(&a->waiters) > 0);
 }
 
-#if !defined(__GLIBC__) && defined(__GNUC__) && __GNUC__ == 12
-#pragma GCC diagnostic pop
-#endif
-
 #define lock_cleanup_pop(a) pthread_cleanup_pop(1)
 
 void cleanup_lock (void * data);

multipathd/Makefile

@@ -5,8 +5,6 @@ CLI      := multipathc
 MANPAGES := multipathd.8
 
 CPPFLAGS += -I$(multipathdir) -I$(mpathutildir) -I$(mpathpersistdir) -I$(mpathcmddir) -I$(thirdpartydir) \
-	$(shell $(PKG_CONFIG) --modversion liburcu 2>/dev/null | \
-		awk -F. '{ printf("-DURCU_VERSION=0x%06x", 256 * ( 256 * $$1 + $$2) + $$3); }') \
 	-DBINDIR='"$(bindir)"' $(SYSTEMD_CPPFLAGS)
 
 #