[dpdk-dev,v8,1/4] compat: Add infrastructure to support symbol versioning

diff --git a/lib/Makefile b/lib/Makefile
index 0ffc982..d617d81 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -31,6 +31,7 @@ 
 
 include $(RTE_SDK)/mk/rte.vars.mk
 
+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..0bab870
--- /dev/null
+++ b/lib/librte_compat/Makefile
@@ -0,0 +1,38 @@ 
+#   BSD LICENSE
+#
+#   Copyright(c) 2013 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.install.mk
diff --git a/lib/librte_compat/rte_compat.h b/lib/librte_compat/rte_compat.h
new file mode 100644
index 0000000..d7cc176
--- /dev/null
+++ b/lib/librte_compat/rte_compat.h
@@ -0,0 +1,117 @@ 
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010 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_
+#include <rte_common.h>
+
+#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.
+ *
+ * 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);
+ *
+ * 4) Implement a new version of foo.
+ * 	char foo(int value, int otherval) { ...}
+ *
+ * 5) Mark the newest version as the default version
+ * 	BIND_DEFAULT_SYMBOL(foo, 1.9);
+ *
+ */
+
+/* 
+ * Macro Parameters:
+ * b - function base name
+ * e - function version extension, to be concatenated with base name
+ * n - function symbol version string to be applied
+ */
+
+/*
+ * VERSION_SYMBOL
+ * Creates a symbol version table entry binding symbol <b>@DPDK_<n> to the internal
+ * function name <b>_<e>
+ */ 
+#define VERSION_SYMBOL(b, e, n) __asm__(".symver " RTE_STR(b) RTE_STR(e) ", "RTE_STR(b)"@DPDK_"RTE_STR(n))
+
+/*
+ * BASE_SYMBOL
+ * Creates a symbol version table entry binding unversioned symbol <b> 
+ * to the internal function <b>_<e>
+ */ 
+#define BASE_SYMBOL(b, e) __asm__(".symver " RTE_STR(b) RTE_STR(e) ", "RTE_STR(b)"@")
+
+/*
+ * BNID_DEFAULT_SYMBOL
+ * Creates a symbol version entry instructing the linker to bind references to
+ * symbol <b> to the internal symbol <b>_<e>
+ */
+#define BIND_DEFAULT_SYMBOL(b, e, n) __asm__(".symver " RTE_STR(b) RTE_STR(e) ", "RTE_STR(b)"@@DPDK_"RTE_STR(n))
+#define __vsym __attribute__((used))
+
+#else
+/*
+ * No symbol versioning in use
+ */
+#define VERSION_SYMBOL(b, e, v)
+#define __vsym
+#define BASE_SYMBOL(b, n)
+#define BIND_DEFAULT_SYMBOL(b, v)
+
+/*
+ * RTE_BUILD_SHARED_LIB=n
+ */
+#endif
+
+
+#endif /* _RTE_COMPAT_H_ */
diff --git a/mk/rte.lib.mk b/mk/rte.lib.mk
index 81bf8e1..1d3b646 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=$(SRCDIR)/$(EXPORT_MAP)
+
 endif
 
+
 _BUILD = $(LIB)
 _INSTALL = $(INSTALL-FILES-y) $(SYMLINK-FILES-y) $(RTE_OUTPUT)/lib/$(LIB)
 _CLEAN = doclean