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From: Neil Horman <nhorman@tuxdriver.com>
To: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 1/4] compat: Add infrastructure to support symbol versioning
Date: Tue, 23 Sep 2014 10:58:29 -0400
Message-ID: <20140923145829.GB12884@hmsreliant.think-freely.org> (raw)
In-Reply-To: <20140923103923.GA4642@sivswdev02.ir.intel.com>

On Tue, Sep 23, 2014 at 11:39:29AM +0100, Sergio Gonzalez Monroy wrote:
> Hi Neil,
> 
> On Mon, Sep 15, 2014 at 03:23:48PM -0400, Neil Horman wrote:
> > 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>
> > ---
> >  lib/Makefile                   |  1 +
> >  lib/librte_compat/Makefile     | 38 +++++++++++++++++++
> >  lib/librte_compat/rte_compat.h | 86 ++++++++++++++++++++++++++++++++++++++++++
> >  mk/rte.lib.mk                  |  6 +++
> >  4 files changed, 131 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..a61511a
> > --- /dev/null
> > +++ b/lib/librte_compat/Makefile
> > @@ -0,0 +1,38 @@
> > +#   BSD LICENSE
> > +#
> > +#   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
> > +#   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..6d65a53
> > --- /dev/null
> > +++ b/lib/librte_compat/rte_compat.h
> > @@ -0,0 +1,86 @@
> > +/*-
> > + *   BSD LICENSE
> > + *
> > + *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
> > + *   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_SYMBOL_VERSIONING
> > +
> > +/*
> > + * 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_1.8 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);
> > + *
> > + */
> > +#define VERSION_SYMBOL(b, e, v) __asm__(".symver " SA(b) SA(e) ", "SA(b)"@DPDK_"SA(v))
> > +#define __vsym __attribute__((used))
> > +
> 
> I may be missing something here but would it not be neccessary to define a
> default symbol?
> Otherwise there would be multiple definitions of a given symbol and the linker
> won't know which symbol version to bind to.
> 
> Following your example, something along these lines:
>  4) Edit lib/<library>/library_version.map to add a DPDK_1.9 node that is a
>    successor to DPDK_1.8, in which foo is exported as a global symbol 
>    DPDK_1.9 {
>       global: foo;
>    } DPDK_1.8;
> 
>  5) rename new function int foo(int index) to
>    int __vsym foo_v19(int index)
> 
>  6) Add this macro immediately below the function:
>    DEFAULT_SYMBOL(foo, _v19, 1.9);
> 
> #define DEFAULT_SYMBOL(b, e, v) __asm__(".symver " SA(b) SA(e) ", "SA(b)"@@DPDK_"SA(v))
> 

You're spot on (though the macro that I created in rte_compat.h is
VERSION_SYMBOL).  

When you use a version script to create a DSO, at link time, the appropriate
version is appended to the symbol name (you can see it with objdump -t in a
linked binary).  If you want to update the symbol to a new version, you do what
I documented in the header file (though now that I re-read it, it could be more
clear.  Hows this for a change to the documentation:

To make a new version of a function foo in a DSO:

1) Edit lib/<library>/library_version.map to add a DPDK_1.8 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 the new version of the function foo.


Those steps above will create two symbols in your export table of the DSO:

foo@@DPDK_1.8
foo@@DPDK_1.9

Any application linked against this DSO will link against the latest version
(DPDK_1.9).  But if you look at the symbols referenced in a binary linked
against an older version of the same DSO, you'll note they explicitly look for
foo@@DPDK_1.8.  Thats how we provide backwards compatibility

Does that answer your questions?

Neil

> > +#else
> > +/*
> > + * No symbol versioning in use
> > + */
> > +#define VERSION_SYMBOL(b, e, v)
> > +#define __vsym
> > +
> > +/*
> > + * RTE_SYMBOL_VERSIONING
> > + */
> > +#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
> > 
> 
> Sergio
> 

  reply	other threads:[~2014-09-23 14:52 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-15 19:23 [dpdk-dev] [PATCH 0/4] Add DSO symbol versioning to support backwards compatibility Neil Horman
2014-09-15 19:23 ` [dpdk-dev] [PATCH 1/4] compat: Add infrastructure to support symbol versioning Neil Horman
2014-09-23 10:39   ` Sergio Gonzalez Monroy
2014-09-23 14:58     ` Neil Horman [this message]
2014-09-23 16:29       ` Sergio Gonzalez Monroy
2014-09-23 17:31         ` Neil Horman
2014-09-25 18:52   ` [dpdk-dev] [PATCH 1/4 v2] " Neil Horman
2014-09-26 14:16     ` Sergio Gonzalez Monroy
2014-09-26 15:16       ` Neil Horman
2014-09-26 15:33         ` Sergio Gonzalez Monroy
2014-09-26 16:22           ` Neil Horman
2014-09-26 19:19             ` Neil Horman
2014-09-29 15:44   ` [dpdk-dev] [PATCH 1/4 v3] " Neil Horman
2014-09-30  8:13     ` Sergio Gonzalez Monroy
2014-09-30 15:18   ` [dpdk-dev] [PATCH 1/4 v4] " Neil Horman
2014-10-01 10:15     ` Sergio Gonzalez Monroy
2014-10-01 10:38       ` Neil Horman
2014-10-01 11:28     ` Sergio Gonzalez Monroy
2014-09-15 19:23 ` [dpdk-dev] [PATCH 2/4] Provide initial versioning for all DPDK libraries Neil Horman
2014-09-19  9:45   ` Bruce Richardson
2014-09-19 10:22     ` Neil Horman
2014-10-01 11:25   ` Sergio Gonzalez Monroy
2014-10-01 14:43     ` Neil Horman
2014-09-15 19:23 ` [dpdk-dev] [PATCH 3/4] Add library version extenstion Neil Horman
2014-10-01 11:27   ` Sergio Gonzalez Monroy
2014-09-15 19:23 ` [dpdk-dev] [PATCH 4/4] docs: Add ABI documentation Neil Horman
2014-10-01 16:06   ` Sergio Gonzalez Monroy
2014-09-18 18:23 ` [dpdk-dev] [PATCH 0/4] Add DSO symbol versioning to support backwards compatibility Thomas Monjalon
2014-09-18 19:14   ` Neil Horman
2014-09-19  8:57     ` Richardson, Bruce
2014-09-19 14:18     ` Venkatesan, Venky
2014-09-19 17:45       ` Neil Horman
2014-09-24 18:19     ` Neil Horman
2014-09-26 10:41       ` Thomas Monjalon
2014-09-26 14:45         ` Neil Horman
2014-09-26 22:02           ` Stephen Hemminger
2014-09-27  2:22             ` Neil Horman
2014-10-01 18:59           ` Neil Horman
2014-10-07 21:01             ` Neil Horman
2014-10-08 15:57               ` Thomas Monjalon
2014-10-08 18:46                 ` Butler, Siobhan A
2014-10-08 19:09                 ` Neil Horman
2014-12-20 21:01 [dpdk-dev] Add DSO symbol versioning to supportbackwards compatibility Neil Horman
2014-12-20 21:01 ` [dpdk-dev] [PATCH 1/4] compat: Add infrastructure to support symbol versioning Neil Horman
2014-12-22 14:01   ` Gonzalez Monroy, Sergio
2014-12-22 16:22     ` Neil Horman
2014-12-22 16:34     ` Neil Horman
2014-12-22 17:09       ` Gonzalez Monroy, Sergio
2014-12-22 19:00         ` Neil Horman
2014-12-22 20:04           ` Neil Horman

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