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

[Neil Horman]

On Fri, Sep 26, 2014 at 03:16:08PM +0100, Sergio Gonzalez Monroy wrote:
> On Thu, Sep 25, 2014 at 02:52:32PM -0400, Neil Horman wrote:
> > 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 at tuxdriver.com>
> > CC: Thomas Monjalon <thomas.monjalon at 6wind.com>
> > CC: "Richardson, Bruce" <bruce.richardson at intel.com>
> > CC: "Gonzalez Monroy, Sergio" <sergio.gonzalez.monroy at 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 at 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 at 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
> > + *
> 
> By removing the symbol from the previous node in the version map, you make
> it local instead of global and applications linked against DPDK 1.8 will fail
> with the new library.
> 
It sounds like you just did the remove part, and not the add part.  What does
your new version map file look like?

Neil

> Following the steps you describe, if we create a new version of the function
> rte_acl_create we would end up with the following dso:
> 
> $ readelf -s x86_64-native-linuxapp-gcc/lib/librte_acl.so | grep "create\|\.symtab\|\.dynsym"
> Symbol table '.dynsym' contains 42 entries:
>     28: 0000000000001990   627 FUNC    GLOBAL DEFAULT   12 rte_acl_create@@DPDK_1.9
> Symbol table '.symtab' contains 147 entries:
>     94: 0000000000001960    36 FUNC    LOCAL  DEFAULT   12 rte_acl_create_v18
>    105: 0000000000001960    36 FUNC    LOCAL  DEFAULT   12 rte_acl_create@@DPDK_1.8
>    138: 0000000000001990   627 FUNC    GLOBAL DEFAULT   12 rte_acl_create
> 
> You can check that applications linked with the old lib will fail to run.
> Note that to easily check this you should define the environment variable
> LD_BIND_NOW to resolve all symbols at program startup (man ld.so).
> 
> Sergio
> 
> > + * 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
> > 
>