On 06 Apr 09:28, Jeff Law wrote:
> On 04/06/2015 09:17 AM, Ilya Enkovich wrote:
> >>
> >>To tell the truth, I can't figure out what this means from a user
> >>perspective. How does a user know whether the linker option is
> >>being ignored, or if they have a new enough linker? If the linker
> >>available at configuration time doesn't support the option, does
> >>that mean the option will never be passed and users will never know
> >>that there are gaping holes in the pointer bounds checking?
> >>
> >>My suggestion would be to pass the option unconditionally and make
> >>the documentation say something like
> >
> >This option was rejected.
> Right. There really isn't a good option here because we don't have
> the infrastructure to query the linker's capabilities at link time.
>
> Though I do wonder if we could issue a warning in the case where the
> configure test indicated -z bndplt was not supported.
>
> It'd obviously mean a link warning every time an end user tried to
> use that toolchain to create a DSO or executable with MPX
> protection. But that may be better than silently leaving some code
> unprotected.
>
>
> Jeff
>
Hi,
Here is a patch to add a note in case we build dynamic MPX codes and don't pass
'-z bndplt'. Does it look OK?
Thanks,
Ilya
--
gcc/
2015-05-26 Ilya Enkovich <enkovich....@gmail.com>
* config/i386/linux-common.h (MPX_SPEC): Add link
warning.
libmpx/
2015-05-26 Ilya Enkovich <enkovich....@gmail.com>
* configure.ac: Add link_mpx_warning.
* libmpx.spec.in: Likewise.
* configure: Regenerate.
diff --git a/gcc/config/i386/linux-common.h b/gcc/config/i386/linux-common.h
index dd79ec6..fcaab81 100644
--- a/gcc/config/i386/linux-common.h
+++ b/gcc/config/i386/linux-common.h
@@ -61,7 +61,8 @@ along with GCC; see the file COPYING3. If not see
#ifndef MPX_SPEC
#define MPX_SPEC "\
- %{mmpx:%{fcheck-pointer-bounds:%{!static:%:include(libmpx.spec)%(link_mpx)}}}"
+ %{mmpx:%{fcheck-pointer-bounds:%{!static:%:include(libmpx.spec)%(link_mpx) \
+ %(link_mpx_warning)}}}"
#endif
#ifndef LIBMPX_SPEC
diff --git a/libmpx/configure.ac b/libmpx/configure.ac
index 463e855..7e9ef86 100644
--- a/libmpx/configure.ac
+++ b/libmpx/configure.ac
@@ -40,17 +40,22 @@ AM_CONDITIONAL(LIBMPX_SUPPORTED, [test "x$LIBMPX_SUPPORTED"
= "xyes"])
link_libmpx="-lpthread"
link_mpx=""
+link_mpx_warning=""
AC_MSG_CHECKING([whether ld accepts -z bndplt])
echo "int main() {};" > conftest.c
if AC_TRY_COMMAND([${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"
+ link_mpx_warning="%{mmpx:}"
else
AC_MSG_RESULT([no])
+ link_mpx="%{mmpx:}"
+ link_mpx_warning="%nGCC was configured with a linker with no '-z bndplt'
support. It significantly reduces MPX coverage for dynamic codes. It is
strongly recommended to use GCC properly configured for MPX."
fi
AC_SUBST(link_libmpx)
AC_SUBST(link_mpx)
+AC_SUBST(link_mpx_warning)
AM_INIT_AUTOMAKE(foreign no-dist no-dependencies)
AM_ENABLE_MULTILIB(, ..)
diff --git a/libmpx/libmpx.spec.in b/libmpx/libmpx.spec.in
index 34d0bdf..854f13d 100644
--- a/libmpx/libmpx.spec.in
+++ b/libmpx/libmpx.spec.in
@@ -3,3 +3,5 @@
*link_libmpx: @link_libmpx@
*link_mpx: @link_mpx@
+
+*link_mpx_warning: @link_mpx_warning@
