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[dm-devel] [PATCH v2] configure: Introduce --enable-symvers option



Only few libc (e.g. glibc) libraries support full symbol version
resolution in runtime. There are lot of standard libraries that do not
support that, such as dietlibc, musl and uclibc. Hence there is no
reason to generate symbol versions when compiling against them.

Additionally libdevmapper.so was broken when compiled against
uclibc. Runtime linker loader caused calling dm_task_get_info_base()
function recursively, leading to segmentation fault.

Introduce --enable-symvers[=STYLE] option, which allows to choose
between gnu and disabled symbol versioning. By default gnu symbol
versioning is used to provide backward compatibility.
__GNUC__ check is replaced now with GNU_SYMVER, which is generated by
configure script. Additionally ld version script is included only in
case of gnu option, which slightly reduces output size.

Providing --disable-symvers to configure script when building against
uclibc library fixes segmentation fault error described above, due to
lack of several versions of the same symbol in libdevmapper.so
library.
---
Patch was developed and tested on top of 2018-06-01-stable branch.

Changes v1 -> v2:
 * Set LDDEPS only when --enable-symvers=gnu

 WHATS_NEW                 |  1 +
 configure                 | 32 ++++++++++++++++++++++++++++++--
 configure.ac              | 28 +++++++++++++++++++++++++---
 include/configure.h.in    |  3 +++
 lib/misc/lib.h            | 10 +++++-----
 libdm/datastruct/bitset.c |  5 +----
 libdm/ioctl/libdm-iface.c |  2 +-
 libdm/libdm-deptree.c     |  2 +-
 libdm/libdm-stats.c       |  2 +-
 9 files changed, 68 insertions(+), 17 deletions(-)

diff --git a/WHATS_NEW b/WHATS_NEW
index bdd2fa635..2279c4275 100644
--- a/WHATS_NEW
+++ b/WHATS_NEW
@@ -1,5 +1,6 @@
 Version 2.02.181 - 
 =================================
+  Introduce --enable-symvers[=STYLE] switch.
 
 Version 2.02.180 - 19th July 2018
 =================================
diff --git a/configure b/configure
index 7d945dfa8..94cd6b1ea 100755
--- a/configure
+++ b/configure
@@ -975,6 +975,7 @@ enable_fsadm
 enable_blkdeactivate
 enable_dmeventd
 enable_selinux
+enable_symvers
 enable_nls
 with_localedir
 with_confdir
@@ -1725,6 +1726,9 @@ Optional Features:
   --disable-blkdeactivate disable blkdeactivate
   --enable-dmeventd       enable the device-mapper event daemon
   --disable-selinux       disable selinux support
+  --enable-symvers[=STYLE]
+                          enables symbol versioning of the shared library
+                          [default=gnu]
   --enable-nls            enable Native Language Support
 
 Optional Packages:
@@ -3156,7 +3160,6 @@ if test -z "$CFLAGS"; then :
 fi
 case "$host_os" in
 	linux*)
-		CLDFLAGS="$CLDFLAGS -Wl,--version-script,.export.sym"
 		# equivalent to -rdynamic
 		ELDFLAGS="-Wl,--export-dynamic"
 		# FIXME Generate list and use --dynamic-list=.dlopen.sym
@@ -3178,7 +3181,6 @@ case "$host_os" in
 		;;
 	darwin*)
 		CFLAGS="$CFLAGS -no-cpp-precomp -fno-common"
-		CLDFLAGS="$CLDFLAGS"
 		ELDFLAGS=
 		CLDWHOLEARCHIVE="-all_load"
 		CLDNOWHOLEARCHIVE=
@@ -14401,6 +14403,32 @@ done
 	LIBS=$lvm_saved_libs
 fi
 
+################################################################################
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to enable symbol versioning" >&5
+$as_echo_n "checking whether to enable symbol versioning... " >&6; }
+# Check whether --enable-symvers was given.
+if test "${enable_symvers+set}" = set; then :
+  enableval=$enable_symvers;
+  case "$enableval" in
+    gnu|no) ;;
+    *) as_fn_error $? "Unknown argument to enable/disable symvers" "$LINENO" 5 ;;
+  esac
+else
+  enable_symvers=gnu
+fi
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $enable_symvers" >&5
+$as_echo "$enable_symvers" >&6; }
+
+if test x$GCC = xyes && test x$enable_symvers = xgnu ; then
+
+$as_echo "#define GNU_SYMVER 1" >>confdefs.h
+
+  case "$host_os" in
+    linux*) CLDFLAGS="$CLDFLAGS -Wl,--version-script,.export.sym" ;;
+  esac
+fi
+
 ################################################################################
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to enable internationalisation" >&5
 $as_echo_n "checking whether to enable internationalisation... " >&6; }
diff --git a/configure.ac b/configure.ac
index e427708cd..2e8712f92 100644
--- a/configure.ac
+++ b/configure.ac
@@ -30,13 +30,11 @@ AC_CANONICAL_TARGET([])
 AS_IF([test -z "$CFLAGS"], [COPTIMISE_FLAG="-O2"])
 case "$host_os" in
 	linux*)
-		CLDFLAGS="$CLDFLAGS -Wl,--version-script,.export.sym"
 		# equivalent to -rdynamic
 		ELDFLAGS="-Wl,--export-dynamic"
 		# FIXME Generate list and use --dynamic-list=.dlopen.sym
 		CLDWHOLEARCHIVE="-Wl,-whole-archive"
 		CLDNOWHOLEARCHIVE="-Wl,-no-whole-archive"
-		LDDEPS="$LDDEPS .export.sym"
 		LIB_SUFFIX=so
 		DEVMAPPER=yes
 		BUILD_LVMETAD=no
@@ -52,7 +50,6 @@ case "$host_os" in
 		;;
 	darwin*)
 		CFLAGS="$CFLAGS -no-cpp-precomp -fno-common"
-		CLDFLAGS="$CLDFLAGS"
 		ELDFLAGS=
 		CLDWHOLEARCHIVE="-all_load"
 		CLDNOWHOLEARCHIVE=
@@ -1656,6 +1653,31 @@ package as well (which may be called readline-devel or something similar).])
 	LIBS=$lvm_saved_libs
 fi
 
+################################################################################
+dnl -- Symbol versioning
+AC_MSG_CHECKING(whether to enable symbol versioning)
+AC_ARG_ENABLE(symvers,
+              AC_HELP_STRING([--enable-symvers[[[=STYLE]]]],
+                             [enables symbol versioning of the shared library [default=gnu]]),
+                             [
+  case "$enableval" in
+    gnu|no) ;;
+    *) AC_MSG_ERROR(Unknown argument to enable/disable symvers) ;;
+  esac],
+                             enable_symvers=gnu)
+AC_MSG_RESULT($enable_symvers)
+
+if test x$GCC = xyes && test x$enable_symvers = xgnu ; then
+  AC_DEFINE(GNU_SYMVER, 1,
+            [Define to use GNU versioning in the shared library.])
+  case "$host_os" in
+    linux*)
+      CLDFLAGS="$CLDFLAGS -Wl,--version-script,.export.sym"
+      LDDEPS="$LDDEPS .export.sym"
+      ;;
+  esac
+fi
+
 ################################################################################
 dnl -- Internationalisation stuff
 AC_MSG_CHECKING(whether to enable internationalisation)
diff --git a/include/configure.h.in b/include/configure.h.in
index 15fd150ed..7a07a10ef 100644
--- a/include/configure.h.in
+++ b/include/configure.h.in
@@ -147,6 +147,9 @@
 /* Path to fsadm binary. */
 #undef FSADM_PATH
 
+/* Define to use GNU versioning in the shared library. */
+#undef GNU_SYMVER
+
 /* Define to 1 if you have the `alarm' function. */
 #undef HAVE_ALARM
 
diff --git a/lib/misc/lib.h b/lib/misc/lib.h
index d7fa5c721..7cf98f932 100644
--- a/lib/misc/lib.h
+++ b/lib/misc/lib.h
@@ -41,16 +41,16 @@
  * macro DM_EXPORT_SYMBOL to export the function and bind it to the
  * specified version string.
  *
- * Since versioning is only available when compiling with GCC the entire
- * compatibility version should be enclosed in '#if defined(__GNUC__)',
- * for example:
+ * Since versioning is only available when compiling with GCC
+ * and GLIBC the entire compatibility version should be enclosed
+ * in '#if defined(GNU_SYMVER)', for example:
  *
  *   int dm_foo(int bar)
  *   {
  *     return bar;
  *   }
  *
- *   #if defined(__GNUC__)
+ *   #if defined(GNU_SYMVER)
  *   // Backward compatible dm_foo() version 1.02.104
  *   int dm_foo_v1_02_104(void);
  *   int dm_foo_v1_02_104(void)
@@ -67,7 +67,7 @@
  * versions of library symbols prior to the introduction of symbol
  * versioning: it must never be used for new symbols.
  */
-#if defined(__GNUC__)
+#if defined(GNU_SYMVER)
 #define DM_EXPORT_SYMBOL(func, ver) \
 	__asm__(".symver " #func "_v" #ver ", " #func "@DM_" #ver )
 #define DM_EXPORT_SYMBOL_BASE(func) \
diff --git a/libdm/datastruct/bitset.c b/libdm/datastruct/bitset.c
index b0826e1eb..2ec3f8f84 100644
--- a/libdm/datastruct/bitset.c
+++ b/libdm/datastruct/bitset.c
@@ -242,7 +242,7 @@ bad:
 	return NULL;
 }
 
-#if defined(__GNUC__)
+#if defined(GNU_SYMVER)
 /*
  * Maintain backward compatibility with older versions that did not
  * accept a 'min_num_bits' argument to dm_bitset_parse_list().
@@ -253,7 +253,4 @@ dm_bitset_t dm_bitset_parse_list_v1_02_129(const char *str, struct dm_pool *mem)
 	return dm_bitset_parse_list(str, mem, 0);
 }
 DM_EXPORT_SYMBOL(dm_bitset_parse_list, 1_02_129);
-
-#else /* if defined(__GNUC__) */
-
 #endif
diff --git a/libdm/ioctl/libdm-iface.c b/libdm/ioctl/libdm-iface.c
index 769b69c1b..28e2eadee 100644
--- a/libdm/ioctl/libdm-iface.c
+++ b/libdm/ioctl/libdm-iface.c
@@ -2145,7 +2145,7 @@ void dm_lib_exit(void)
 	_version_checked = 0;
 }
 
-#if defined(__GNUC__)
+#if defined(GNU_SYMVER)
 /*
  * Maintain binary backward compatibility.
  * Version script mechanism works with 'gcc' compatible compilers only.
diff --git a/libdm/libdm-deptree.c b/libdm/libdm-deptree.c
index ab0545659..00651c0b2 100644
--- a/libdm/libdm-deptree.c
+++ b/libdm/libdm-deptree.c
@@ -3797,7 +3797,7 @@ void dm_tree_node_set_callback(struct dm_tree_node *dnode,
 	dnode->callback_data = data;
 }
 
-#if defined(__GNUC__)
+#if defined(GNU_SYMVER)
 /*
  * Backward compatible implementations.
  *
diff --git a/libdm/libdm-stats.c b/libdm/libdm-stats.c
index 94ad380e0..76efbbe35 100644
--- a/libdm/libdm-stats.c
+++ b/libdm/libdm-stats.c
@@ -5065,7 +5065,7 @@ int dm_stats_start_filemapd(int fd, uint64_t group_id, const char *path,
  * current dm_stats_create_region() version.
  */
 
-#if defined(__GNUC__)
+#if defined(GNU_SYMVER)
 int dm_stats_create_region_v1_02_106(struct dm_stats *dms, uint64_t *region_id,
 				     uint64_t start, uint64_t len, int64_t step,
 				     int precise, const char *program_id,
-- 
2.18.0


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