[dpdk-dev] [PATCH 1/4 v2] compat: Add infrastructure to support symbol versioning

[Neil Horman <nhorman@tuxdriver.com>]

Add initial pass header files to support symbol versioning.

---
Change notes
v2)
* Fixed ifdef in rte_compat.h to test for RTE_BUILD_SHARED_LIB instead of the
non-existant RTE_SYMBOL_VERSIONING

* Fixed VERSION_SYMBOL macro to add the needed extra @ to make versioning work
properly

* Improved/Clarified documentation

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Thomas Monjalon <thomas.monjalon@6wind.com>
CC: "Richardson, Bruce" <bruce.richardson@intel.com>
CC: "Gonzalez Monroy, Sergio" <sergio.gonzalez.monroy@intel.com>
---
 lib/Makefile                   |  1 +
 lib/librte_compat/Makefile     | 38 ++++++++++++++++++
 lib/librte_compat/rte_compat.h | 87 ++++++++++++++++++++++++++++++++++++++++++
 mk/rte.lib.mk                  |  6 +++
 4 files changed, 132 insertions(+)
 create mode 100644 lib/librte_compat/Makefile
 create mode 100644 lib/librte_compat/rte_compat.h

diff --git a/lib/Makefile b/lib/Makefile
index 10c5bb3..a85b55b 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -32,6 +32,7 @@
 include $(RTE_SDK)/mk/rte.vars.mk
 
 DIRS-$(CONFIG_RTE_LIBC) += libc
+DIRS-y += librte_compat
 DIRS-$(CONFIG_RTE_LIBRTE_EAL) += librte_eal
 DIRS-$(CONFIG_RTE_LIBRTE_MALLOC) += librte_malloc
 DIRS-$(CONFIG_RTE_LIBRTE_RING) += librte_ring
diff --git a/lib/librte_compat/Makefile b/lib/librte_compat/Makefile
new file mode 100644
index 0000000..3415c7b
--- /dev/null
+++ b/lib/librte_compat/Makefile
@@ -0,0 +1,38 @@
+#   BSD LICENSE
+#
+#   Copyright(c) 2010-2014 Neil Horman <nhorman@tuxdriver.com>
+#   All rights reserved.
+#
+#   Redistribution and use in source and binary forms, with or without
+#   modification, are permitted provided that the following conditions
+#   are met:
+#
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above copyright
+#       notice, this list of conditions and the following disclaimer in
+#       the documentation and/or other materials provided with the
+#       distribution.
+#     * Neither the name of Intel Corporation nor the names of its
+#       contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+#   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+#   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+#   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+#   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+#   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+#   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+#   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+#   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+#   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+#   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+#   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+include $(RTE_SDK)/mk/rte.vars.mk
+
+
+# install includes
+SYMLINK-y-include := rte_compat.h
+
+include $(RTE_SDK)/mk/rte.lib.mk
diff --git a/lib/librte_compat/rte_compat.h b/lib/librte_compat/rte_compat.h
new file mode 100644
index 0000000..cff9aea
--- /dev/null
+++ b/lib/librte_compat/rte_compat.h
@@ -0,0 +1,87 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010-2014 Neil Horman <nhorman@tuxdriver.com>.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _RTE_COMPAT_H_
+#define _RTE_COMPAT_H_
+
+/*
+ * This is just a stringification macro for use below.
+ */
+#define SA(x) #x
+
+#ifdef RTE_BUILD_SHARED_LIB
+
+/*
+ * Provides backwards compatibility when updating exported functions.
+ * When a symol is exported from a library to provide an API, it also provides a
+ * calling convention (ABI) that is embodied in its name, return type,
+ * arguments, etc.  On occasion that function may need to change to accomodate
+ * new functionality, behavior, etc.  When that occurs, it is desireable to
+ * allow for backwards compatibility for a time with older binaries that are
+ * dynamically linked to the dpdk.  to support that the __vsym and
+ * VERSION_SYMBOL macros are created.  They, in conjunction with the
+ * <library>_version.map file for a given library allow for multiple versions of
+ * a symbol to exist in a shared library so that older binaries need not be
+ * immediately recompiled. Their use is outlined in the following example:
+ * Assumptions: DPDK 1.(X) contains a function int foo(char *string)
+ *              DPDK 1.(X+1) needs to change foo to be int foo(int index)
+ *
+ * To accomplish this:
+ * 1) Edit lib/<library>/library_version.map to add a DPDK_1.(X+1) node, in which
+ * foo is exported as a global symbol.  Note that foo must be removed from the
+ * DPDK.(X) node, or you will see multiple symbol definitions
+ *
+ * 2) rename the existing function int foo(char *string) to 
+ * 	int __vsym foo_v18(char *string)
+ *
+ * 3) Add this macro immediately below the function
+ * 	VERSION_SYMBOL(foo, _v18, 1.8);
+ *
+ */
+#define VERSION_SYMBOL(b, e, v) __asm__(".symver " SA(b) SA(e) ", "SA(b)"@@DPDK_"SA(v))
+#define __vsym __attribute__((used))
+
+#else
+/*
+ * No symbol versioning in use
+ */
+#define VERSION_SYMBOL(b, e, v)
+#define __vsym
+
+/*
+ * RTE_BUILD_SHARED_LIB
+ */
+#endif
+
+
+#endif /* _RTE_COMPAT_H_ */
diff --git a/mk/rte.lib.mk b/mk/rte.lib.mk
index f458258..82ac309 100644
--- a/mk/rte.lib.mk
+++ b/mk/rte.lib.mk
@@ -40,8 +40,12 @@ VPATH += $(SRCDIR)
 
 ifeq ($(RTE_BUILD_SHARED_LIB),y)
 LIB := $(patsubst %.a,%.so,$(LIB))
+
+CPU_LDFLAGS += --version-script=$(EXPORT_MAP)
+
 endif
 
+
 _BUILD = $(LIB)
 _INSTALL = $(INSTALL-FILES-y) $(SYMLINK-FILES-y) $(RTE_OUTPUT)/lib/$(LIB)
 _CLEAN = doclean
@@ -160,7 +164,9 @@ endif
 $(RTE_OUTPUT)/lib/$(LIB): $(LIB)
 	@echo "  INSTALL-LIB $(LIB)"
 	@[ -d $(RTE_OUTPUT)/lib ] || mkdir -p $(RTE_OUTPUT)/lib
+ifneq ($(LIB),)
 	$(Q)cp -f $(LIB) $(RTE_OUTPUT)/lib
+endif
 
 #
 # Clean all generated files
-- 
1.9.3