Re: [dpdk-dev] [PATCH v4 1/4] compat: Add infrastructure to support symbol versioning

["Gray, Mark D" <mark.d.gray@intel.com>]

I agree in principle with this patchset. OVS links with DPDK and providing stability in the ABI/API (and the Policy to manage this) makes deployment easier for OVS when linking with shared dpdk libs. It should also be easy for us to track changes in the API through the deprecation notices making development easier! 

Good job.

Acked-by: Mark D. Gray <mark.d.gray@intel.com>

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Neil Horman
> Sent: Thursday, January 15, 2015 7:35 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH v4 1/4] compat: Add infrastructure to support
> symbol versioning
> 
> Add initial pass header files to support symbol versioning.
> 
> 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>
> 
> ---
> Change Notes:
> V2)
> 	Moved ifeq to _INSTALL target
> 
> V3)
> 	Undo V2 changes and make librte_compat use the rte.install.mk file
> instead
> 
> v4)
> 	changed --version-script to accept SRCDIR in this patch at per request
> 	documented versioning macros
> 	cleaned up macro parameter consistency
> 	converted SA macro to RTE_STR macro
> 	fixed copyright
> ---
>  lib/Makefile                   |   1 +
>  lib/librte_compat/Makefile     |  38 +++++++++++++
>  lib/librte_compat/rte_compat.h | 117
> +++++++++++++++++++++++++++++++++++++++++
>  mk/rte.lib.mk                  |   4 ++
>  4 files changed, 160 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 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
> --
> 2.1.0