[Bug ld/18878] New: _savegpr1_XXX crashes when called through a stub on POWERPC64LE

[dougkwan at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18878

            Bug ID: 18878
           Summary: _savegpr1_XXX crashes when called through a stub on
                    POWERPC64LE
           Product: binutils
           Version: 2.24
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: dougkwan at google dot com
  Target Milestone: ---

Created attachment 8556
  --> https://sourceware.org/bugzilla/attachment.cgi?id=8556&action=edit
test case for bug

I have found problem in which a big powerpc64le binary crashes when compiled
with -Os.  I chased down the root cause to be calling runtime functions
_savegpr1_XXX via branch stubs.  These functions do not follow the normal ABI
and take the value of r12 as the argument.  Unfortunately, branch stubs and
PLTs also use r12 as a scratch register during address calculation.  So the
stubs clobber the argument to _savegpr1_XXX and cause SEGV faults.

Attached is a test case. I tried it on a POWER8 machine running ubuntu.  The
test crashes if compiled with -Os using both ld and gold.

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/powerpc64le-linux-gnu/4.8/lto-wrapper
Target: powerpc64le-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.8.2-19ubuntu1'
--with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.8 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libmudflap
--disable-libsanitizer --disable-libquadmath --enable-plugin --with-system-zlib
--disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-ppc64el/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-ppc64el
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-ppc64el
--with-arch-directory=ppc64el --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-secureplt --with-cpu=power7 --with-tune=power8
--disable-multilib --enable-multiarch --disable-werror --with-long-double-128
--enable-checking=release --build=powerpc64le-linux-gnu
--host=powerpc64le-linux-gnu --target=powerpc64le-linux-gnu
Thread model: posix
gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1)

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