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@xxxxxxxxxx>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Fine with me...
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--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)
> - ])
>
