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authorErlang/OTP <[email protected]>2018-11-23 09:44:30 +0100
committerErlang/OTP <[email protected]>2018-11-23 09:44:30 +0100
commitd5b77a045544a018a5a7af7c200089c5f3837d2a (patch)
tree9272f5944bad144b93bdcfab9ec0ebd945aa5a63
parentdb35a04a38f9501b921beac2c46576c5fa13e75a (diff)
parentda9268d342e3f0f21b43fb55788f6e60aac55e71 (diff)
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Merge branch 'john/erts/spectre-configure-flag-otp_20/OTP-15430/ERIERL-237' into maint-21
* john/erts/spectre-configure-flag-otp_20/OTP-15430/ERIERL-237: Allow disabling retpoline in interpreter loop Add a ./configure flag for spectre mitigation
-rw-r--r--erts/configure.in50
-rw-r--r--erts/emulator/beam/beam_emu.c1
2 files changed, 51 insertions, 0 deletions
diff --git a/erts/configure.in b/erts/configure.in
index bcdc6cd083..4a27b532de 100644
--- a/erts/configure.in
+++ b/erts/configure.in
@@ -388,6 +388,56 @@ if test X"$with_ets_write_concurrency_locks" != X""; then
[Define to override the default number of write_concurrency locks])
fi
+AC_ARG_WITH(spectre-mitigation,
+ AS_HELP_STRING([--with-spectre-mitigation={yes|incomplete}],
+ [enable spectre mitigation, either fully or with mitigations
+ disabled in a handful places like the interpreter])
+ AS_HELP_STRING([--without-spectre-mitigation],
+ [build without spectre mitigation]),
+ [],[with_spectre_mitigation=no])
+
+case "$with_spectre_mitigation" in
+ no) ;;
+ yes) ;;
+ incomplete) ;;
+ *) AC_MSG_ERROR([Invalid spectre mitigation setting]) ;;
+esac
+
+i_noretpoline_attr=""
+
+if test X"$with_spectre_mitigation" != X"no"; then
+ CFLAGS="$CFLAGS -mindirect-branch=thunk"
+
+ AC_MSG_CHECKING([for spectre mitigation])
+ AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM([],[return 0;])],
+ [AC_MSG_RESULT([yes])],
+ [AC_MSG_ERROR([no])])
+
+ if test X"$with_spectre_mitigation" = X"incomplete"; then
+ # gcc and clang support this attribute if they're recent enough. Note
+ # that we must compile with -Werror to check for actual support as they
+ # warn rather than error out on unsupported attributes.
+
+ i_noretpoline_attr='__attribute__((__indirect_branch__("keep")))'
+ i_preserve_cflags="$CFLAGS"
+ CFLAGS="$CFLAGS -Werror"
+
+ AC_MSG_CHECKING([whether spectre mitigation can be disabled on a per-function basis])
+ AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM([$i_noretpoline_attr],[return 0;])],
+ [AC_MSG_RESULT([yes])],
+ [AC_MSG_ERROR([no])])
+
+ CFLAGS="$i_preserve_cflags"
+ fi
+fi
+
+AC_DEFINE_UNQUOTED(ERTS_NO_RETPOLINE, $i_noretpoline_attr,
+ [Per-function attribute for disabling retpoline. This is
+ *only* defined when --with-spectre-mitigation=incomplete
+ and has no effects otherwise])
+
dnl ----------------------------------------------------------------------
dnl Checks for programs.
dnl ----------------------------------------------------------------------
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index ab5920a67e..e909a0b4da 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -579,6 +579,7 @@ init_emulator(void)
* the instructions' C labels to the loader.
* The second call starts execution of BEAM code. This call never returns.
*/
+ERTS_NO_RETPOLINE
void process_main(Eterm * x_reg_array, FloatDef* f_reg_array)
{
static int init_done = 0;