Re: [PATCH] change ifunc assembly test to a link test

[Andrew Pinski <pinskia at gmail dot com>]

On Mon, Oct 22, 2012 at 8:54 PM, Mike Frysinger <vapier@gentoo.org> wrote:
> The test currently tests the binutils frontend support which passes for
> all versions of binutils we currently require (2.20+).  It doesn't test
> the backend which is required for ifunc to actually work, and which most
> targets don't yet support.
>
> Change the assembly code so that when we link it, we get a file that has
> ifunc relocations if the backend supports it.  That way we can test to
> see if binutils supports everything we need.
>
> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
>
> 2012-10-22  Mike Frysinger  <vapier@gentoo.org>
>
>         * configure.in: Move READELF check to start of file.
>         (libc_cv_asm_gnu_indirect_function): Change to a link test.
>         * configure: Regenerated.
> ---
>  configure    | 205 +++++++++++++++++++++++++++++++----------------------------
>  configure.in |  21 ++++--
>  2 files changed, 122 insertions(+), 104 deletions(-)
> diff --git a/configure.in b/configure.in
> index 3af030a..de33fe6 100644
> --- a/configure.in
> +++ b/configure.in
> @@ -23,6 +23,7 @@ AC_SUBST(cross_compiling)
>  AC_PROG_CPP
>  # We need the C++ compiler only for testing.
>  AC_PROG_CXX
> +AC_CHECK_TOOL(READELF, readelf, false)
>
>  if test "`cd $srcdir; /bin/pwd`" = "`/bin/pwd`"; then
>    AC_MSG_ERROR([you must configure in a separate build directory])
> @@ -571,12 +572,21 @@ AC_CACHE_CHECK([for assembler gnu_indirect_function symbol type support],
>                libc_cv_asm_gnu_indirect_function, [dnl
>  cat > conftest.s <<EOF
>  .type foo,%gnu_indirect_function
> +foo:
> +.globl _start
> +_start:

I think you should also include __start in that .s file as MIPS uses
__start as the start function.  Even though the test will fail on MIPS
right now, it is a good idea to have it working partly so that it
works in the future when ifunc support is included.

Thanks,
Andrew Pinski


> +.data
> +.long foo
>  EOF
> -if ${CC-cc} -c $ASFLAGS conftest.s 1>&AS_MESSAGE_LOG_FD 2>&AS_MESSAGE_LOG_FD;
> -then
> -  libc_cv_asm_gnu_indirect_function=yes
> -else
> -  libc_cv_asm_gnu_indirect_function=no
> +libc_cv_asm_gnu_indirect_function=no
> +if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS \
> +           -nostartfiles -nostdlib \
> +           -o conftest conftest.s 1>&AS_MESSAGE_LOG_FD 2>&AS_MESSAGE_LOG_FD; then
> +  # Do a link to see if the backend supports IFUNC relocs.
> +  $READELF -r conftest 1>&AS_MESSAGE_LOG_FD
> +  if ! LC_ALL=C $READELF -r conftest | grep -q 'no relocations'; then
> +    libc_cv_asm_gnu_indirect_function=yes
> +  fi
>  fi
>  rm -f conftest*])
>
> @@ -930,7 +940,6 @@ AC_CHECK_PROG_VER(AWK, gawk, --version,
>    [GNU Awk[^0-9]*\([0-9][0-9.]*\)],
>    [[3-9].*], critic_missing="$critic_missing gawk")
>
> -AC_CHECK_TOOL(READELF, readelf, false)
>  AC_CHECK_TOOL(NM, nm, false)
>
>  AC_CHECK_PROGS(AUTOCONF, autoconf, no)
> --
> 1.7.12
>