Re: [dm-devel] [PATCH v3 38/38] libmultipath: avoid -Warray-bounds error in uatomic operations

[Benjamin Marzinski <bmarzins@redhat.com>]

On Thu, Sep 14, 2023 at 04:51:31PM +0200, mwilck@suse.com wrote:
> From: Martin Wilck <mwilck@suse.com>
> 
> 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 adding a workaround for uatomic_xchg(),
> and introduce the macro URCU_VERSION (originally only used for multipathd)
> globally.
> 
Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
> Signed-off-by: Martin Wilck <mwilck@suse.com>
> ---
>  Makefile.inc         |  2 +-
>  create-config.mk     |  5 +++++
>  libmultipath/alias.c |  5 +++--
>  libmultipath/lock.h  | 23 ++++++++++++++---------
>  multipathd/Makefile  |  2 --
>  5 files changed, 23 insertions(+), 14 deletions(-)
> 
> diff --git a/Makefile.inc b/Makefile.inc
> index 6e384e6..04bfa56 100644
> --- a/Makefile.inc
> +++ b/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)\" \
> diff --git a/create-config.mk b/create-config.mk
> index d125597..4d318b9 100644
> --- a/create-config.mk
> +++ b/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)" >>$@
> diff --git a/libmultipath/alias.c b/libmultipath/alias.c
> index e5d3f15..74431f3 100644
> --- a/libmultipath/alias.c
> +++ b/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
> @@ -300,7 +301,7 @@ 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
> @@ -775,7 +776,7 @@ 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) {
> diff --git a/libmultipath/lock.h b/libmultipath/lock.h
> index 9814be7..ac80d1d 100644
> --- a/libmultipath/lock.h
> +++ b/libmultipath/lock.h
> @@ -13,17 +13,22 @@ struct mutex_lock {
>  	int waiters; /* uatomic access only */
>  };
>  
> -#if !defined(__GLIBC__) && defined(__GNUC__) && __GNUC__ == 12
> -#pragma GCC diagnostic push
> -#pragma GCC diagnostic ignored "-Warray-bounds"
> -#endif
> -
>  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 int uatomic_xchg_int(int *ptr, int val)
> +{
> +	return uatomic_xchg(ptr, val);
> +}
> +
>  static inline void lock(struct mutex_lock *a)
>  {
>  	uatomic_inc(&a->waiters);
> @@ -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);
> diff --git a/multipathd/Makefile b/multipathd/Makefile
> index cdba3db..0ba6ecb 100644
> --- a/multipathd/Makefile
> +++ b/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)
>  
>  #
> -- 
> 2.42.0
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