diff --git a/development/rust/rust.SlackBuild b/development/rust/rust.SlackBuild
index 27c29bbd90..a8c8a44210 100644
--- a/development/rust/rust.SlackBuild
+++ b/development/rust/rust.SlackBuild
@@ -38,27 +38,59 @@ TAG=${TAG:-_SBo}
 
 if [ -z "$ARCH" ]; then
   case "$( uname -m )" in
-    i?86) ARCH=i686 ;;
-    armv7*) ARCH=$( uname -m ) ;;
+    i?86) ARCH=i586 ;;
     arm*) ARCH=arm ;;
        *) ARCH=$( uname -m ) ;;
   esac
 fi
 
+# if you already have rust and cargo installed, you can bootstrap from the
+# previous version.
+if [ "$LOCAL_BOOTSTRAP" = "" ] && [ -x /usr/bin/cargo ] && [ -x /usr/bin/rustc ] ; then
+  LOCAL_BOOTSTRAP=yes
+fi
+
+# https://forge.rust-lang.org/platform-support.html
 # Bootstrapping ARCH:
 if [ "$ARCH" = "i586" ]; then
-  BARCH="i686"
-elif case $ARCH in armv7*) true;; *) false;; esac; then
-  BARCH="armv7"
+  if [ "$LOCAL_BOOTSTRAP" = "yes" ] ; then
+    if rustc -Vv | grep host | grep i586 > /dev/null ; then
+      BARCH="$ARCH"
+    else
+      echo "Your exising rust cannot bootstrap an i586 toolchain. Either set LOCAL_BOOTSTRAP=no or remove your existing rust package and do a full bootstrap."
+      exit 1
+    fi
+  else
+    # i586 must be built on a i686 machine, since the bootstrap compiler is i686
+    BARCH="i686"
+
+    if case "$( uname -m )" in i586) true ;; *) false ;; esac ; then
+      echo "rust must be bootstrapped from an i686 machine"
+      exit 1
+    fi
+  fi
 else
   BARCH="$ARCH"
 fi
 
+TARCH="$ARCH"
+
 # Bootstrapping ABI:
-if case $ARCH in armv7*) true;; *) false;; esac; then
-  BABI="gnueabihf"
-elif [ "$ARCH" = "arm" ]; then
-  BABI="gnueabi"
+if [ "$ARCH" = "arm" ]; then
+  if readelf -h /bin/bash | grep Flags | grep hard > /dev/null 2>&1 ; then
+    # hardfloat
+    BABI="gnueabihf"
+    BARCH="armv7"
+    TARCH="$BARCH"
+  else
+    # softfloat
+    BABI="gnueabi"
+
+    if case "$( uname -m )" in armv5*) true ;; *) false ;; esac ; then
+      echo "rust must be bootstrapped from an armv6 machine or later"
+      exit 1
+    fi
+  fi
 else
   BABI="gnu"
 fi
@@ -77,9 +109,13 @@ elif [ "$ARCH" = "i686" ]; then
 elif [ "$ARCH" = "x86_64" ]; then
   SLKCFLAGS="-O2 -fPIC"
   LIBDIRSUFFIX="64"
-elif case $ARCH in armv7*) true;; *) false;; esac; then
-  SLKCFLAGS="-O2 -march=armv7-a -mfpu=vfpv3-d16"
+elif [ "$ARCH" = "arm" ] ; then
+  SLKCFLAGS="-O2"
   LIBDIRSUFFIX=""
+
+  if [ "$BABI" = "gnueabihf" ] ; then
+    SLKCFLAGS="$SLKCFLAGS -march=armv7-a -mfpu=vfpv3-d16 -mfloat-abi=hard"
+  fi
 else
   SLKCFLAGS="-O2"
   LIBDIRSUFFIX=""
@@ -94,12 +130,6 @@ rm -rf $SRCNAM-$VERSION-src
 tar xvf $CWD/$SRCNAM-$VERSION-src.tar.gz
 cd $SRCNAM-$VERSION-src
 
-# if you already have rust and cargo installed, you can bootstrap from the
-# previous version.
-if [ "$LOCAL_BOOTSTRAP" = "" ] && [ -x /usr/bin/cargo ] && [ -x /usr/bin/rustc ] ; then
-  LOCAL_BOOTSTRAP=yes
-fi
-
 if [ "$LOCAL_BOOTSTRAP" != "yes" ] ; then
   # rust requires bootstrapping with the previous rust version.
   # versions are defined in src/stage0.txt
@@ -108,6 +138,11 @@ if [ "$LOCAL_BOOTSTRAP" != "yes" ] ; then
      $CWD/$SRCNAM-$RSTAGE0_VERSION-$BARCH-unknown-linux-$BABI.tar.gz \
      build/cache/$RSTAGE0_DIR
 
+  if [ "$TARCH" = "i586" ] ; then
+    cp $CWD/$PRGNAM-std-$RSTAGE0_VERSION-$TARCH-unknown-linux-$BABI.tar.gz \
+       build/cache/$RSTAGE0_DIR
+  fi
+
   mkdir -p build/cache/$CSTAGE0_DIR
   cp $CWD/cargo-$CSTAGE0_VERSION-$BARCH-unknown-linux-$BABI.tar.gz build/cache/$CSTAGE0_DIR
 fi
@@ -115,6 +150,9 @@ fi
 # src/bootstrap/config.toml.example
 cat << EOF > config.toml
 [build]
+build = "$BARCH-unknown-linux-$BABI"
+host = ["$TARCH-unknown-linux-$BABI"]
+target = ["$TARCH-unknown-linux-$BABI"]
 vendor = true
 extended = true
 
@@ -126,12 +164,24 @@ mandir = "man"
 
 [rust]
 codegen-units = 0
-debuginfo = true
+debuginfo = false
 channel = "stable"
 rpath = false
 codegen-tests = false
 
-[target.$BARCH-unknown-linux-$BABI]
+[target.i586-unknown-linux-gnu]
+llvm-config = "/usr/bin/llvm-config"
+
+[target.i686-unknown-linux-gnu]
+llvm-config = "/usr/bin/llvm-config"
+
+[target.x86_64-unknown-linux-gnu]
+llvm-config = "/usr/bin/llvm-config"
+
+[target.arm-unknown-linux-gnuabi]
+llvm-config = "/usr/bin/llvm-config"
+
+[target.armv7-unknown-linux-gnuabihf]
 llvm-config = "/usr/bin/llvm-config"
 EOF
 
@@ -146,7 +196,37 @@ find -L . \
  \( -perm 666 -o -perm 664 -o -perm 640 -o -perm 600 -o -perm 444 \
   -o -perm 440 -o -perm 400 \) -exec chmod 644 {} \;
 
-export RUSTFLAGS="$RUSTFLAGS -C link-args=-lffi"
+if [ "$BARCH" = "i686" ] && [ "$TARCH" = "i586" ] ; then
+  # this will cause some messages like:
+  # warning: redundant linker flag specified for library `m`
+  # but will keep the build from falling over when doing the stage1 compiler
+  # linking for the i586 compiler. seems the correct flags don't get passed
+  # through and we end up failures like:
+  # error: linking with `clang` failed: exit code: 1
+  # /tmp/SBo/rustc-1.20.0-src/build/i686-unknown-linux-gnu/stage1-rustc/i586-unknown-linux-gnu/release/deps/librustc_llvm-4ab259c9aed547db.so: undefined reference to `xxx`
+  export RUSTFLAGS="$RUSTFLAGS -C link-args=-lffi -lrt -ldl -lcurses -lpthread -lz -lm"
+else
+  # https://github.com/rust-lang/rust/issues/39880
+  # $ llvm-config --system-libs
+  # -lrt -ldl -lcurses -lpthread -lz -lm
+  export RUSTFLAGS="$RUSTFLAGS -C link-args=-lffi"
+fi
+
+export PKG_CONFIG_ALLOW_CROSS=1
+
+if [ "$BARCH" = "i586" ] ; then
+  # when bootstrapping from i586 (rust already installed), also build a i686
+  # rustlib
+
+  # from config.toml.example:
+
+  # In addition to all host triples, other triples to produce the standard library
+  # for. Each host triple will be used to produce a copy of the standard library
+  # for each target triple.
+  #target = ["x86_64-unknown-linux-gnu"] # defaults to just the build triple
+
+  sed -i 's/^target =.*$/target = ["i686-unknown-linux-gnu"]/' config.toml
+fi
 
 # README.md says gcc 4.7 / clang 3.x or later needed
 # but building fails for me with GCC 5.3 from slackware 14.2
@@ -165,7 +245,7 @@ DESTDIR=$PKG python x.py install
 #rm -f $PKG/usr/lib$LIBDIRSUFFIX/rustlib/rust-installer-version
 #rm -f $PKG/usr/lib$LIBDIRSUFFIX/rustlib/uninstall.sh
 # Make sure the paths are correct, though:
-sed -i "s,/tmp/package-rust/,/,g" $PKG/usr/lib$LIBDIRSUFFIX/rustlib/install.log $PKG/usr/lib$LIBDIRSUFFIX/rustlib/manifest-*
+sed -i "s,$PKG/,/,g" $PKG/usr/lib$LIBDIRSUFFIX/rustlib/install.log $PKG/usr/lib$LIBDIRSUFFIX/rustlib/manifest-*
 # And a little compression doesn't hurt either:
 gzip -9 $PKG/usr/lib$LIBDIRSUFFIX/rustlib/manifest-*
 
diff --git a/development/rust/rust.info b/development/rust/rust.info
index e534c1e549..72d406a16a 100644
--- a/development/rust/rust.info
+++ b/development/rust/rust.info
@@ -3,10 +3,12 @@ VERSION="1.20.0"
 HOMEPAGE="https://www.rust-lang.org"
 DOWNLOAD="https://static.rust-lang.org/dist/rustc-1.20.0-src.tar.gz \
           https://static.rust-lang.org/dist/2017-07-20/cargo-0.20.0-i686-unknown-linux-gnu.tar.gz \
+          https://static.rust-lang.org/dist/2017-07-20/rust-std-1.19.0-i586-unknown-linux-gnu.tar.gz \
           https://static.rust-lang.org/dist/2017-07-20/rust-std-1.19.0-i686-unknown-linux-gnu.tar.gz \
           https://static.rust-lang.org/dist/2017-07-20/rustc-1.19.0-i686-unknown-linux-gnu.tar.gz"
 MD5SUM="1d3c5d25d8e6215e7d0b6d4d4c9835b9 \
         1de2d0fb8e09d3c976ac8d874f158f57 \
+        20462edfd584959cf48d24772fc224ff \
         7e7d4a768fe05264fc23cb2afef75740 \
         9711f634011658b451f315916234c88e"
 DOWNLOAD_x86_64="https://static.rust-lang.org/dist/rustc-1.20.0-src.tar.gz \