[Bug target/65612] Multiversioning doesn't work with DSO nor PIE

[hjl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65612

--- Comment #7 from hjl at gcc dot gnu.org <hjl at gcc dot gnu.org> ---
Author: hjl
Date: Fri Apr 17 12:58:07 2015
New Revision: 222178

URL: https://gcc.gnu.org/viewcvs?rev=222178&root=gcc&view=rev
Log:
Hide __cpu_indicator_init/__cpu_model from linker

We shouldn't call external function, __cpu_indicator_init, while an object
is being relocated since its .got.plt section hasn't been updated.  It
works for non-PIE since no update on .got.plt section is required.  This
patch creates libgcc.so as a linker script, hides __cpu_indicator_init
and __cpu_model in libgcc.so.1 from linker, forces linker to resolve
__cpu_indicator_init and __cpu_model to their hidden definitions in
libgcc.a while providing backward binary compatibility.

gcc/testsuite/

    PR target/65612
    * g++.dg/ext/mv18.C: New test.
    * g++.dg/ext/mv19.C: Likewise.
    * g++.dg/ext/mv20.C: Likewise.
    * g++.dg/ext/mv21.C: Likewise.
    * g++.dg/ext/mv22.C: Likewise.
    * g++.dg/ext/mv23.C: Likewise.

libgcc/

    PR target/65612
    * config.host (tmake_file): Add t-slibgcc-libgcc for Linux/x86.
    * config/i386/cpuinfo.c (__cpu_model): Initialize.
    (__cpu_indicator_init@GCC_4.8.0): New.
    (__cpu_model@GCC_4.8.0): Likewise.
    * config/i386/t-linux (HOST_LIBGCC2_CFLAGS): Add
    -DUSE_ELF_SYMVER.

Added:
    trunk/gcc/testsuite/g++.dg/ext/mv18.C
    trunk/gcc/testsuite/g++.dg/ext/mv19.C
    trunk/gcc/testsuite/g++.dg/ext/mv20.C
    trunk/gcc/testsuite/g++.dg/ext/mv21.C
    trunk/gcc/testsuite/g++.dg/ext/mv22.C
    trunk/gcc/testsuite/g++.dg/ext/mv23.C
Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/libgcc/ChangeLog
    trunk/libgcc/config.host
    trunk/libgcc/config/i386/cpuinfo.c
    trunk/libgcc/config/i386/t-linux