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author | Marek Habersack <grendel@twistedcode.net> | 2018-01-31 20:10:31 +0300 |
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committer | Marek Safar <marek.safar@gmail.com> | 2018-02-02 16:53:02 +0300 |
commit | 4a995045915dbe45918787d158485dda26660e05 (patch) | |
tree | 6996135227386cc531c9ccba9bebc8e7f9a90346 /m4 | |
parent | 9b3e3187d99a6dfaf49df3346dbabb5625c235ed (diff) |
Check for compiler switches to mitigate Spectre/Meltdown
This commit implements checking whether the compiler used to build mono supports
the recently added switches to generate code designed to mitigate the effects of
the Spectre/Meltdown bugs of the modern CPUs (https://meltdownattack.com/).
As of this commit the options are implemented for GCC 8.x, 7.3 and backported to
some older versions of gcc 7.x (e.g. in Ubuntu). The options tested for, and
used, here are:
-mindirect-branch (https://gcc.gnu.org/onlinedocs/gcc-7.3.0/gcc/x86-Options.html#index--mindirect-branch)
-mfunction-return (https://gcc.gnu.org/onlinedocs/gcc-7.3.0/gcc/x86-Options.html#index--mfunction-return)
Checks and usage of the above flags is hidden behind the
`--with-spectre-mitigation` configure option, defaulting to `no`.
Two additional options are implemented to specify the kind of thunk to implement
by each of the flags above:
--with-spectre-indirect-branch-choice=keep,thunk,inline,extern
Convert indirect branches to the specified kind of thunk (defaults to inline)
--with-spectre-function-return-choice=keep,thunk,inline,extern
Convert function return instructions to the specified kind of
thunk (defaults to inline)
Diffstat (limited to 'm4')
-rw-r--r-- | m4/ax_check_compile_flag.m4 | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/m4/ax_check_compile_flag.m4 b/m4/ax_check_compile_flag.m4 new file mode 100644 index 00000000000..dcabb92a141 --- /dev/null +++ b/m4/ax_check_compile_flag.m4 @@ -0,0 +1,74 @@ +# =========================================================================== +# https://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html +# =========================================================================== +# +# SYNOPSIS +# +# AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT]) +# +# DESCRIPTION +# +# Check whether the given FLAG works with the current language's compiler +# or gives an error. (Warnings, however, are ignored) +# +# ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on +# success/failure. +# +# If EXTRA-FLAGS is defined, it is added to the current language's default +# flags (e.g. CFLAGS) when the check is done. The check is thus made with +# the flags: "CFLAGS EXTRA-FLAGS FLAG". This can for example be used to +# force the compiler to issue an error when a bad flag is given. +# +# INPUT gives an alternative input source to AC_COMPILE_IFELSE. +# +# NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this +# macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG. +# +# LICENSE +# +# Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de> +# Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com> +# +# This program is free software: you can redistribute it and/or modify it +# under the terms of the GNU General Public License as published by the +# Free Software Foundation, either version 3 of the License, or (at your +# option) any later version. +# +# This program is distributed in the hope that it will be useful, but +# WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General +# Public License for more details. +# +# You should have received a copy of the GNU General Public License along +# with this program. If not, see <https://www.gnu.org/licenses/>. +# +# As a special exception, the respective Autoconf Macro's copyright owner +# gives unlimited permission to copy, distribute and modify the configure +# scripts that are the output of Autoconf when processing the Macro. You +# need not follow the terms of the GNU General Public License when using +# or distributing such scripts, even though portions of the text of the +# Macro appear in them. The GNU General Public License (GPL) does govern +# all other use of the material that constitutes the Autoconf Macro. +# +# This special exception to the GPL applies to versions of the Autoconf +# Macro released by the Autoconf Archive. When you make and distribute a +# modified version of the Autoconf Macro, you may extend this special +# exception to the GPL to apply to your modified version as well. + +#serial 5 + +AC_DEFUN([AX_CHECK_COMPILE_FLAG], +[AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF +AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl +AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [ + ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS + _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1" + AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])], + [AS_VAR_SET(CACHEVAR,[yes])], + [AS_VAR_SET(CACHEVAR,[no])]) + _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags]) +AS_VAR_IF(CACHEVAR,yes, + [m4_default([$2], :)], + [m4_default([$3], :)]) +AS_VAR_POPDEF([CACHEVAR])dnl +])dnl AX_CHECK_COMPILE_FLAGS |