[RFC PATCH 1/7] add --enable-safe-stack configuration option

["LeMay, Michael" <michael.lemay@intel.com>]

The SafeStack sanitizer in LLVM Clang seeks to mitigate stack memory
corruption vulnerabilities [1].  That sanitizer can be used with
varying levels of runtime support, which has an effect on the
program's level of resistance to various types of attacks.  This patch
adds a configuration option to enable a segmentation-hardened form of
the SafeStack sanitizer for 32-bit x86 Linux programs.  Subsequent
patches implement and describe various aspects of the hardening.

[1] http://clang.llvm.org/docs/SafeStack.html

Signed-off-by: Michael LeMay <michael.lemay@intel.com>
---
  configure | 5 +++++
  1 file changed, 5 insertions(+)

diff --git a/configure b/configure
index 969671d..c83c4d1 100755
--- a/configure
+++ b/configure
@@ -34,6 +34,7 @@ Optional features:
    --enable-wrapper=...    build given musl toolchain wrapper [auto]
    --disable-shared        inhibit building shared library [enabled]
    --disable-static        inhibit building static library [enabled]
+  --enable-safe-stack     enable segmentation-hardened SafeStack [disabled]

  Some influential environment variables:
    CC                      C compiler command [detected]
@@ -139,6 +140,7 @@ static=yes
  wrapper=auto
  gcc_wrapper=no
  clang_wrapper=no
+SAFE_STACK=no

  for arg ; do
  case "$arg" in
@@ -170,6 +172,8 @@ case "$arg" in
  --disable-wrapper|--enable-wrapper=no) wrapper=no ;;
  --enable-gcc-wrapper|--enable-gcc-wrapper=yes) wrapper=yes ; 
gcc_wrapper=yes ;;
  --disable-gcc-wrapper|--enable-gcc-wrapper=no) wrapper=no ;;
+--enable-safe-stack|--enable-safe-stack=yes) SAFE_STACK=yes ;;
+--disable-safe-stack|--enable-safe-stack=no) SAFE_STACK=no ;;
  --enable-*|--disable-*|--with-*|--without-*|--*dir=*|--build=*) ;;
  --host=*|--target=*) target=${arg#*=} ;;
  -* ) echo "$0: unknown option $arg" ;;
@@ -732,6 +736,7 @@ OPTIMIZE_GLOBS = $OPTIMIZE_GLOBS
  ALL_TOOLS = $tools
  TOOL_LIBS = $tool_libs
  ADD_CFI = $ADD_CFI
+SAFE_STACK = $SAFE_STACK
  EOF
  test "x$static" = xno && echo "STATIC_LIBS ="
  test "x$shared" = xno && echo "SHARED_LIBS ="
-- 
2.7.4