[PATCH, libmpx, i386, PR driver/65444] Pass '-z bndplt' when building dynamic objects with MPX

[H.J. Lu]

On Wed, Mar 18, 2015 at 5:13 AM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
> 2015-03-18 15:08 GMT+03:00 H.J. Lu <hjl.tools@gmail.com>:
>> On Wed, Mar 18, 2015 at 5:05 AM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
>>> 2015-03-18 15:02 GMT+03:00 H.J. Lu <hjl.tools@gmail.com>:
>>>> On Wed, Mar 18, 2015 at 4:56 AM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
>>>>> Hi,
>>>>>
>>>>> This patch fixes PR target/65444 by passing '-z bndplt' to linker when appropriate.  Bootstrapped and tested on x86_64-unknown-linux-gnu.  Will commit it to trunk in a couple of days if no objections arise.
>>>>>
>>>>> Thanks,
>>>>> Ilya
>>>>> --
>>>>> gcc/
>>>>>
>>>>> 2015-03-18  Ilya Enkovich  <ilya.enkovich@intel.com>
>>>>>
>>>>>         PR driver/65444
>>>>>         * config/i386/linux-common.h (MPX_SPEC): New.
>>>>>         (CHKP_SPEC): Add MPX_SPEC.
>>>>>
>>>>> libmpx/
>>>>>
>>>>> 2015-03-18  Ilya Enkovich  <ilya.enkovich@intel.com>
>>>>>
>>>>>         PR driver/65444
>>>>>         * configure.ac: Add check for '-z bndplt' support
>>>>>         by linker. Add link_mpx output variable.
>>>>>         * libmpx.spec.in (link_mpx): New.
>>>>>         * configure: Regenerate.
>>>>>
>>>>>
>>>>> diff --git a/gcc/config/i386/linux-common.h b/gcc/config/i386/linux-common.h
>>>>> index 9c6560b..dd79ec6 100644
>>>>> --- a/gcc/config/i386/linux-common.h
>>>>> +++ b/gcc/config/i386/linux-common.h
>>>>> @@ -59,6 +59,11 @@ along with GCC; see the file COPYING3.  If not see
>>>>>   %:include(libmpx.spec)%(link_libmpx)"
>>>>>  #endif
>>>>>
>>>>> +#ifndef MPX_SPEC
>>>>> +#define MPX_SPEC "\
>>>>> + %{mmpx:%{fcheck-pointer-bounds:%{!static:%:include(libmpx.spec)%(link_mpx)}}}"
>>>>> +#endif
>>>>> +
>>>>>  #ifndef LIBMPX_SPEC
>>>>>  #if defined(HAVE_LD_STATIC_DYNAMIC)
>>>>>  #define LIBMPX_SPEC "\
>>>>> @@ -89,5 +94,5 @@ along with GCC; see the file COPYING3.  If not see
>>>>>
>>>>>  #ifndef CHKP_SPEC
>>>>>  #define CHKP_SPEC "\
>>>>> -%{!nostdlib:%{!nodefaultlibs:" LIBMPX_SPEC LIBMPXWRAPPERS_SPEC "}}"
>>>>> +%{!nostdlib:%{!nodefaultlibs:" LIBMPX_SPEC LIBMPXWRAPPERS_SPEC "}}" MPX_SPEC
>>>>>  #endif
>>>>> diff --git a/libmpx/configure.ac b/libmpx/configure.ac
>>>>> index fe0d3f2..3f8b50f 100644
>>>>> --- a/libmpx/configure.ac
>>>>> +++ b/libmpx/configure.ac
>>>>> @@ -40,7 +40,18 @@ AC_MSG_RESULT($LIBMPX_SUPPORTED)
>>>>>  AM_CONDITIONAL(LIBMPX_SUPPORTED, [test "x$LIBMPX_SUPPORTED" = "xyes"])
>>>>>
>>>>>  link_libmpx="-lpthread"
>>>>> +link_mpx=""
>>>>> +AC_MSG_CHECKING([whether ld accepts -z bndplt])
>>>>> +echo "int main() {};" > conftest.c
>>>>> +if AC_TRY_COMMAND([${CC} ${CFLAGS} -Wl,-z,bndplt -o conftest conftest.c 1>&AS_MESSAGE_LOG_FD])
>>>>> +then
>>>>> +    AC_MSG_RESULT([yes])
>>>>> +    link_mpx="$link_mpx -z bndplt"
>>>>> +else
>>>>> +    AC_MSG_RESULT([no])
>>>>> +fi
>>>>>  AC_SUBST(link_libmpx)
>>>>> +AC_SUBST(link_mpx)
>>>>>
>>>>
>>>> Without -z bndplt, MPX won't work correctly.  We should always pass -z bndplt
>>>> to linker.  If linker doesn't support it, ld will issue a warning, not
>>>> error and users
>>>> will know their linker is too old.  When they update linker, they don't have to
>>>> rebuild GCC.
>>>
>>> If ld issues a warning instead of an error, then configure test passes
>>> and we pass '-z bndplt' to linker.
>>>
>>
>> Can you verify it with an older linker? The unknown XXX in -z XXX is always
>> warned and ignored in Linux linker.  If testing it on Linux always passes,
>> it is useless.
>
> Old ld issues a warning:
>
> ld: warning: -z bndplt ignored.

Does configure test pass?

> But gold issues an error:
>
> ld.gold: bndplt: unknown -z option
> ld.gold: use the --help option for usage information

If gold is used, MPX won't work.  What should we do here?
Should we hardcode -fuse-ld=bfd for MPX?

-- 
H.J.