#!/bin/sh
# Copyright (C) 2014  Codethink Limited
#
# 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; version 2 of the License.
#
# 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, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
# =*= License: GPL-2 =*=

set -eu

die(){
    echo "$@" >&2
    exit 1
}

shellescape(){
    echo "'$(echo "$1" | sed -e "s/'/'\\''/g")'"
}

########################## END OF COMMON HEADER ###############################
#
# The above lines, as well as being part of this script, are copied into the
# self-installing SDK blob's header script, as a means of re-using content.
#

help(){
    cat <<EOF
sdk.write: Write extension for making an SDK installer.

Description:
  This is a write extension for producing a self-installing SDK blob
  from a configured system.

  It generates a shell script header and appends the rootfs as a tarball,
  which the header later extracts, and performs various configuration
  to have it useable as a relocatable toolchain.

  This is similar to what the shar and makeself programs do, but we
  need custom setup, so shar isn't appropriate, and makeself's api is
  insufficiently flexible for our requirements.

  The toolchain relocation is handled by sedding every text file in the
  SDK directory, and using the patchelf from inside the SDK to change
  every ELF binary in the toolchain to use the linker and libraries from
  inside the SDK.

  The ELF patching is required so that the SDK can work independently
  of the versions of libraries installed on the host system.

Location: Path to create the script at

ENV VARS:
    PREFIX (optional)  The prefix the toolchain is built with
                       defaults to /usr
    TARGET (mandatory) The gnu triplet the toolchain was built with
EOF
}

ROOTDIR="$1"
OUTPUT_SCRIPT="$2"
PREFIX=${PREFIX-/usr}

find_patchelf(){
    # Look for patchelf in the usual places
    for binpath in /bin "$PREFIX/bin"; do
        if [ -x "$ROOTDIR$binpath/patchelf" ]; then
            echo "$binpath/patchelf"
            return
        fi
    done
    die "patchelf not found in rootfs"
}

read_elf_interpreter(){
    # Use readelf and sed to find the interpreter a binary uses this is
    # required since we can't yet guarantee that the deploying system
    # contains patchelf
    readelf --wide --program-headers "$1" |
    sed -nr -f /proc/self/fd/3 3<<'EOF'
/\s+INTERP/{
  n         # linker is on line after INTERP line
  s/^\s*\[Requesting program interpreter: (.*)]$/\1/
  p         # in -n mode, so need to print our text
}
EOF
}

find_lib_paths(){
    local found_first=false
    for libpath in "$PREFIX/lib32" "$PREFIX/lib64" "$PREFIX/lib" \
                   /lib32 /lib64 /lib; do
        if [ -e "$ROOTDIR$libpath" ]; then
            if "$found_first"; then
                printf ":%s" "$libpath"
            else
                printf "%s" "$libpath"
                found_first=true
            fi
        fi
    done
}

# Create script with common header
header_end=$(grep -En -m1 -e '^#+ END OF COMMON HEADER #+$' "$0" | cut -d: -f1)
head -n "$header_end" "$0" | install -m 755 -D /dev/stdin "$OUTPUT_SCRIPT"

# Determine any config
PATCHELF="$(find_patchelf)"
RTLD="$(read_elf_interpreter "$ROOTDIR$PATCHELF")"
LIB_PATH="${LIB_PATH-$(find_lib_paths)}"

# Append deploy-time config to header
cat >>"$OUTPUT_SCRIPT" <<EOF
#################### START OF DEPLOY TIME CONFIGURATION #######################

TARGET=$(shellescape "$TARGET")
PREFIX=$(shellescape "$PREFIX")
PATCHELF=$(shellescape "$PATCHELF")
RTLD=$(shellescape "$RTLD")
LIB_PATH=$(shellescape "$LIB_PATH")

##################### END OF DEPLOY TIME CONFIGURATION ########################
EOF

# Append deployment script
cat >>"$OUTPUT_SCRIPT" <<'EOF'
########################### START OF HEADER SCRIPT ############################

usage(){
    cat <<USAGE
usage: $0 TOOLCHAIN_PATH
USAGE
}

if [ "$#" != 1 ]; then
    echo TOOLCHAIN_PATH not given >&2
    usage >&2
    exit 1
fi

TOOLCHAIN_PATH="$(readlink -f \"$1\")"

sedescape(){
    # Escape the passed in string so it can be safely interpolated into
    # a sed expression as a literal value.
    echo "$1" | sed -e 's/[\/&]/\\&/g'
}

prepend_to_path_elements(){
    # Prepend $1 to every entry in the : separated list specified as $2.
    local prefix="$1"
    (
        # Split path into components
        IFS=:
        set -- $2
        # Print path back out with new prefix
        printf %s "$prefix/$1"
        shift
        for arg in "$@"; do
            printf ":%s" "$prefix/$arg"
        done
    )
}

extract_rootfs(){
    # Extract the bzipped tarball at the end of the script passed as $1
    # to the path specified as $2
    local selfextractor="$1"
    local target="$2"
    local script_end="$(($(\
        grep -aEn -m1 -e '^#+ END OF HEADER SCRIPT #+$' "$selfextractor" |
            cut -d: -f1) + 1 ))"
    mkdir -p "$target"
    tail -n +"$script_end" "$selfextractor" | tar -xj -C "$target" .
}

amend_text_file_paths(){
    # Replace all instances of $3 with $4 in the directory specified by $1
    # excluding the subdirectory $2
    local root="$1"
    local inner_sysroot="$2"
    local old_prefix="$3"
    local new_prefix="$4"
    find "$root" \( -path "$inner_sysroot" -prune \) -o -type f \
        -exec sh -c 'file "$1" | grep -q text' - {} \; \
        -exec sed -i -e \
          "s/$(sedescape "$old_prefix")/$(sedescape "$new_prefix")/g" {} +
}

filter_patchelf_errors(){
    # Filter out warnings from patchelf that are acceptable
    # The warning that it's making a file bigger is just noise
    # The warning about not being an ELF executable just means we got a
    # false positive from file that it was an ELF binary
    # Failing to find .interp is because for convenience, we set the
    # interpreter in the same command as setting the rpath, even though
    # we give it both executables and libraries.
    grep -v -e 'warning: working around a Linux kernel bug' \
            -e 'not an ELF executable' \
            -e 'cannot find section .interp'
}

patch_elves(){
    # Set the interpreter and library paths of ELF binaries in $1,
    # except for the $2 subdirectory, using the patchelf command in the
    # toolchain specified as $3, so that it uses the linker specified
    # as $4 as the interpreter, and the runtime path specified by $5.
    #
    # The patchelf inside the toolchain is used to ensure that it works
    # independently of the availability of patchelf on the host.
    #
    # This is possible by invoking the linker directly and specifying
    # --linker-path as the RPATH we want to set the binaries to use.
    local root="$1"
    local inner_sysroot="$2"
    local patchelf="$3"
    local linker="$4"
    local lib_path="$5"
    find "$root" \( -path "$inner_sysroot" -prune \) -o -type f \
        -type f -perm +u=x \
        -exec sh -c 'file "$1" | grep -q "ELF"' - {} \; \
        -exec "$linker" --library-path "$lib_path" \
                  "$patchelf" --set-interpreter "$linker" \
                              --set-rpath "$lib_path" {} \; 2>&1 \
    | filter_patchelf_errors
}

generate_environment_setup(){
    local target="$1"
    install -m 644 -D /dev/stdin "$target" <<ENVSETUP
export PATH=$(shellescape "$TOOLCHAIN_PATH/usr/bin"):"\$PATH"
export TARGET_PREFIX=$(shellescape "$TARGET"-)
export CC=$(shellescape "$TARGET-gcc")
export CXX=$(shellescape "$TARGET-g++")
export CPP=$(shellescape "$TARGET-gcc -E")
export AS=$(shellescape "$TARGET-as")
export LD=$(shellescape "$TARGET-ld")
export STRIP=$(shellescape "$TARGET-strip")
export RANLIB=$(shellescape "$TARGET-ranlib")
export OBJCOPY=$(shellescape "$TARGET-objcopy")
export OBJDUMP=$(shellescape "$TARGET-objdump")
export AR=$(shellescape "$TARGET-ar")
export NM=$(shellescape "$TARGET-nm")
ENVSETUP
}

SYSROOT="$TOOLCHAIN_PATH$PREFIX/$TARGET/sys-root"
PATCHELF="$TOOLCHAIN_PATH$PATCHELF"
RTLD="$TOOLCHAIN_PATH$RTLD"
OLD_PREFIX="$PREFIX"
NEW_PREFIX="$TOOLCHAIN_PATH/$PREFIX"
RPATH="$(prepend_to_path_elements "$TOOLCHAIN_PATH" "$LIB_PATH")"
ENV_SETUP_FILE="$(dirname "$TOOLCHAIN_PATH")/environment-setup-$TARGET"

echo Writing environment setup script to "$ENV_SETUP_FILE"
generate_environment_setup "$ENV_SETUP_FILE"

echo Extracting rootfs
extract_rootfs "$0" "$TOOLCHAIN_PATH"

echo "Relocating prefix references of $OLD_PREFIX to $NEW_PREFIX in" \
     "the toolchain's textual config files."
amend_text_file_paths "$TOOLCHAIN_PATH" "$SYSROOT" "$OLD_PREFIX" "$NEW_PREFIX"

echo "Patching ELF binary files' interpreter and runtime library paths" \
     "to refer to libraries within the toolchain"
patch_elves "$TOOLCHAIN_PATH" "$SYSROOT" "$PATCHELF" "$RTLD" "$RPATH"

exit
############################ END OF HEADER SCRIPT #############################
EOF

# Append rootfs as tarball
tar -C "$1" -cj >>"$OUTPUT_SCRIPT" .