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

["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.

-- 
H.J.