footprint.sh: improve printed output
diff --git a/scripts/footprint.sh b/scripts/footprint.sh
index a11844f..48cedd8 100755
--- a/scripts/footprint.sh
+++ b/scripts/footprint.sh
@@ -6,6 +6,8 @@
 
 if [ -r $CONFIG_H ]; then :; else
     echo "$CONFIG_H not found" >&2
+    echo "This script needs to be run from the root of" >&2
+    echo "a git checkout or uncompressed tarball" >&2
     exit 1
 fi
 
@@ -14,15 +16,33 @@
     exit 1
 fi
 
+if which arm-none-eabi-gcc >/dev/null 2>&1; then :; else
+    echo "You need the ARM-GCC toolchain in your path" >&2
+    echo "See https://launchpad.net/gcc-arm-embedded/" >&2
+    exit 1
+fi
+
+ARMGCC_FLAGS='-Os -march=armv7-m -mthumb'
+OUTFILE='00-footprint-summary.txt'
+
+log()
+{
+    echo "$@"
+    echo "$@" >> "$OUTFILE"
+}
+
 doit()
 {
     NAME="$1"
     FILE="$2"
 
-    echo "$NAME:"
+    log ""
+    log "$NAME ($FILE):"
 
     cp $CONFIG_H ${CONFIG_H}.bak
-    cp "$FILE" include/mbedtls/config.h
+    if [ "$FILE" != $CONFIG_H ]; then
+        cp "$FILE"  $CONFIG_H
+    fi
 
     {
         scripts/config.pl unset MBEDTLS_NET_C || true
@@ -31,22 +51,44 @@
     } >/dev/null 2>&1
 
     CC=arm-none-eabi-gcc AR=arm-none-eabi-ar LD=arm-none-eabi-ld \
-        CFLAGS='-Wa,--noexecstack -Os -march=armv7-m -mthumb' \
-        make clean lib >/dev/null
+        CFLAGS="$ARMGCC_FLAGS" make clean lib >/dev/null
 
     OUT="size-${NAME}.txt"
     arm-none-eabi-size -t library/libmbed*.a > "$OUT"
-    head -n1 "$OUT"
-    tail -n1 "$OUT"
+    log "$( head -n1 "$OUT" )"
+    log "$( tail -n1 "$OUT" )"
 
     cp ${CONFIG_H}.bak $CONFIG_H
 }
 
+# truncate the file just this time
+echo "(generated by $0)" > "$OUTFILE"
+echo "" >> "$OUTFILE"
+
+log "Footprint of default configurations (minus net.c, timing.c, fs_io)"
+log "for bare-metal ARM Cortex-M3/M4 microcontrollers."
+
+VERSION_H="include/mbedtls/version.h"
+MBEDTLS_VERSION=$( sed -n 's/.*VERSION_STRING *"\(.*\)"/\1/p' $VERSION_H )
+if git rev-parse HEAD >/dev/null; then
+    GIT_HEAD=$( git rev-parse HEAD | head -c 10 )
+    GIT_VERSION=" ($GIT_HEAD)"
+else
+    GIT_VERSION=""
+fi
+
+log ""
+log "mbed TLS $MBEDTLS_VERSION$GIT_VERSION"
+log "$( arm-none-eabi-gcc --version | head -n1 )"
+log "CFLAGS=$ARMGCC_FLAGS"
+
 # creates the yotta config
 yotta/create-module.sh >/dev/null
 
-doit default    include/mbedtls/config.h.bak
+doit default    include/mbedtls/config.h
 doit yotta      yotta/module/mbedtls/config.h
 doit thread     configs/config-thread.h
-doit ecc        configs/config-suite-b.h
+doit suite-b    configs/config-suite-b.h
 doit psk        configs/config-ccm-psk-tls1_2.h
+
+zip mbedtls-footprint.zip "$OUTFILE" size-*.txt >/dev/null