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

[Ilya Enkovich <enkovich.gnu@gmail.com>]

On 23 Mar 13:19, Ilya Enkovich wrote:
> Hi,
> 
> May this patch go into trunk at this point?  It is very important for
> dynamic MPX codes.
> 
> Thanks,
> Ilya
> 

I additionally documented changes in invoke.texi.  OK for trunk?

Thanks,
Ilya
--
gcc/

2015-03-31  Ilya Enkovich  <ilya.enkovich@intel.com>

	PR driver/65444
	* config/i386/linux-common.h (MPX_SPEC): New.
	(CHKP_SPEC): Add MPX_SPEC.
	* doc/invoke.texi (-fcheck-pointer-boudns): Document
	possible issues with '-z bndplt' support in linker.

libmpx/

2015-03-31  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/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index bf8afad..c058710 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -5857,7 +5857,16 @@ MPX-based instrumentation requires
 a runtime library to enable MPX in hardware and handle bounds
 violation signals.  By default when @option{-fcheck-pointer-bounds}
 and @option{-mmpx} options are used to link a program, the GCC driver
-links against the @file{libmpx} runtime library.  MPX-based instrumentation
+links against the @file{libmpx} runtime library and @file{libmpxwrappers}
+library.  It also passes '-z bndplt' to a linker in case it supports this
+option (which is checked on libmpx configuration).  Note that old versions
+of linker may ignore option.  Gold linker doesn't support '-z bndplt'
+option.  With no '-z bndplt' support in linker all calls to dynamic libraries
+lose passed bounds reducing overall protection level.  It's highly
+recommended to use linker with '-z bndplt' support.  In case such linker
+is not available it is adviced to always use @option{-static-libmpxwrappers}
+for better protection level or use @option{-static} to completely avoid
+external calls to dynamic libraries.  MPX-based instrumentation
 may be used for debugging and also may be included in production code
 to increase program security.  Depending on usage, you may
 have different requirements for the runtime library.  The current version
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)
 
 AM_INIT_AUTOMAKE(foreign no-dist no-dependencies)
 AM_ENABLE_MULTILIB(, ..)
diff --git a/libmpx/libmpx.spec.in b/libmpx/libmpx.spec.in
index a265e28..34d0bdf 100644
--- a/libmpx/libmpx.spec.in
+++ b/libmpx/libmpx.spec.in
@@ -1,3 +1,5 @@
 # This spec file is read by gcc when linking.  It is used to specify the
-# standard libraries we need in order to link with libcilkrts.
+# standard libraries we need in order to link with libmpx.
 *link_libmpx: @link_libmpx@
+
+*link_mpx: @link_mpx@