| Message ID | 06935570-ac17-776d-0a9c-cd9158a01922@redhat.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | xfsprogs: remove retpoline support | expand |
On Wed, Oct 10, 2018 at 02:58:40PM -0500, Eric Sandeen wrote: > When it came up that xfsprogs was using retpolines by default, > the gcc folks inside Red Hat expressed ... alarm. I'm not sure > of all the details, but I think the concern was that userspace > support for this is not really quite baked. > > Unless/until there is a demonstrated side-channel which would > warrant retpolines here, let's just remove it for now. > > Cc: Florian Weimer <fweimer@redhat.com> > Signed-off-by: Eric Sandeen <sandeen@redhat.com> Fine with me... Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> --D > --- > > Getting this on the list so we can have a discussion with people who > understand the issues better than I do ... > > diff --git a/configure.ac b/configure.ac > index 5fdf78e..41f1209 100644 > --- a/configure.ac > +++ b/configure.ac > @@ -227,7 +227,6 @@ if test "$enable_lto" = "yes" && test "$have_lto" != "yes"; then > AC_MSG_ERROR([LTO not supported by compiler.]) > fi > > -AC_PACKAGE_CHECK_RETPOLINE > AC_CHECK_SIZEOF([long]) > AC_CHECK_SIZEOF([char *]) > AC_TYPE_UMODE_T > diff --git a/include/builddefs.in b/include/builddefs.in > index f7d39a4..fe529c6 100644 > --- a/include/builddefs.in > +++ b/include/builddefs.in > @@ -166,13 +166,6 @@ LIBICU_CFLAGS = @libicu_CFLAGS@ > SANITIZER_CFLAGS += @addrsan_cflags@ @threadsan_cflags@ @ubsan_cflags@ > SANITIZER_LDFLAGS += @addrsan_ldflags@ @threadsan_ldflags@ @ubsan_ldflags@ > > -# Enable retpolines if available > -HAVE_RETPOLINE = @have_retpoline@ > -ifeq ($(HAVE_RETPOLINE),yes) > -OPTIMIZER += @retpoline_cflags@ > -LOADERFLAGS += @retpoline_ldflags@ > -endif > - > # Use special ar/ranlib wrappers if we have lto > HAVE_LTO = @have_lto@ > ifeq ($(HAVE_LTO),yes) > diff --git a/m4/package_libcdev.m4 b/m4/package_libcdev.m4 > index 0a6b514..52ddac2 100644 > --- a/m4/package_libcdev.m4 > +++ b/m4/package_libcdev.m4 > @@ -446,25 +446,3 @@ AC_DEFUN([AC_PACKAGE_CHECK_LTO], > AC_SUBST(lto_cflags) > AC_SUBST(lto_ldflags) > ]) > - > -AC_DEFUN([AC_PACKAGE_CHECK_RETPOLINE], > - [ AC_MSG_CHECKING([if C compiler supports retpoline]) > - OLD_CFLAGS="$CFLAGS" > - OLD_LDFLAGS="$LDFLAGS" > - RETPOLINE_FLAGS="-mindirect-branch=thunk" > - CFLAGS="$CFLAGS $RETPOLINE_FLAGS" > - LDFLAGS="$LDFLAGS $RETPOLINE_FLAGS" > - AC_LINK_IFELSE([AC_LANG_PROGRAM([])], > - [AC_MSG_RESULT([yes])] > - [retpoline_cflags=$RETPOLINE_FLAGS] > - [retpoline_ldflags=$RETPOLINE_FLAGS], > - [AC_MSG_RESULT([no])]) > - if test -n "$retpoline_cflags"; then > - have_retpoline=yes > - fi > - CFLAGS="${OLD_CFLAGS}" > - LDFLAGS="${OLD_LDFLAGS}" > - AC_SUBST(have_retpoline) > - AC_SUBST(retpoline_cflags) > - AC_SUBST(retpoline_ldflags) > - ]) >
diff --git a/configure.ac b/configure.ac index 5fdf78e..41f1209 100644 --- a/configure.ac +++ b/configure.ac @@ -227,7 +227,6 @@ if test "$enable_lto" = "yes" && test "$have_lto" != "yes"; then AC_MSG_ERROR([LTO not supported by compiler.]) fi -AC_PACKAGE_CHECK_RETPOLINE AC_CHECK_SIZEOF([long]) AC_CHECK_SIZEOF([char *]) AC_TYPE_UMODE_T diff --git a/include/builddefs.in b/include/builddefs.in index f7d39a4..fe529c6 100644 --- a/include/builddefs.in +++ b/include/builddefs.in @@ -166,13 +166,6 @@ LIBICU_CFLAGS = @libicu_CFLAGS@ SANITIZER_CFLAGS += @addrsan_cflags@ @threadsan_cflags@ @ubsan_cflags@ SANITIZER_LDFLAGS += @addrsan_ldflags@ @threadsan_ldflags@ @ubsan_ldflags@ -# Enable retpolines if available -HAVE_RETPOLINE = @have_retpoline@ -ifeq ($(HAVE_RETPOLINE),yes) -OPTIMIZER += @retpoline_cflags@ -LOADERFLAGS += @retpoline_ldflags@ -endif - # Use special ar/ranlib wrappers if we have lto HAVE_LTO = @have_lto@ ifeq ($(HAVE_LTO),yes) diff --git a/m4/package_libcdev.m4 b/m4/package_libcdev.m4 index 0a6b514..52ddac2 100644 --- a/m4/package_libcdev.m4 +++ b/m4/package_libcdev.m4 @@ -446,25 +446,3 @@ AC_DEFUN([AC_PACKAGE_CHECK_LTO], AC_SUBST(lto_cflags) AC_SUBST(lto_ldflags) ]) - -AC_DEFUN([AC_PACKAGE_CHECK_RETPOLINE], - [ AC_MSG_CHECKING([if C compiler supports retpoline]) - OLD_CFLAGS="$CFLAGS" - OLD_LDFLAGS="$LDFLAGS" - RETPOLINE_FLAGS="-mindirect-branch=thunk" - CFLAGS="$CFLAGS $RETPOLINE_FLAGS" - LDFLAGS="$LDFLAGS $RETPOLINE_FLAGS" - AC_LINK_IFELSE([AC_LANG_PROGRAM([])], - [AC_MSG_RESULT([yes])] - [retpoline_cflags=$RETPOLINE_FLAGS] - [retpoline_ldflags=$RETPOLINE_FLAGS], - [AC_MSG_RESULT([no])]) - if test -n "$retpoline_cflags"; then - have_retpoline=yes - fi - CFLAGS="${OLD_CFLAGS}" - LDFLAGS="${OLD_LDFLAGS}" - AC_SUBST(have_retpoline) - AC_SUBST(retpoline_cflags) - AC_SUBST(retpoline_ldflags) - ])
When it came up that xfsprogs was using retpolines by default, the gcc folks inside Red Hat expressed ... alarm. I'm not sure of all the details, but I think the concern was that userspace support for this is not really quite baked. Unless/until there is a demonstrated side-channel which would warrant retpolines here, let's just remove it for now. Cc: Florian Weimer <fweimer@redhat.com> Signed-off-by: Eric Sandeen <sandeen@redhat.com> --- Getting this on the list so we can have a discussion with people who understand the issues better than I do ...