#!/bin/bash

# Compile server for systemtap
#
# Copyright (C) 2008 Red Hat Inc.
#
# This file is part of systemtap, and is free software.  You can
# redistribute it and/or modify it under the terms of the GNU General
# Public License (GPL); either version 2, or (at your option) any
# later version.

# This script unpacks the tar file provided on stdin and uses the information
# contained in the unpacked tree to build the requested systemtap kernel module.
# This module is then written to stdout.

#-----------------------------------------------------------------------------
# Helper functions.
#-----------------------------------------------------------------------------
# function: configuration
function configuration {
    # Configuration
    tmpdir_prefix_client=stap.client
    tmpdir_prefix_server=stap.server
    port=$1
    test "X$port" = "X" && port=65001
}

# function: initialization
function initialization {
    # Initialization
    wd=`pwd`

    # Default options settings
    p_phase=5
    keep_temps=0
}

# function: receive_request
#
# Receive a tar file representing the request from the client:
# The protocol is:
#   client -> "request:"
#   server -> "ready:"
#   client -> $tar_client
function receive_request {
    # Request from the client is on stdin
    read
    line=$REPLY

    # Check to see that it is a client request
    test "$line" = "request:" || \
	fatal "ERROR: client request, '$line' is incorrect"

    # Create a place to receive the client's tar file
    tar_client=`mktemp -t $tmpdir_prefix_server.client.tgz.XXXXXX` || \
	fatal "ERROR: cannot create temporary tar file " $tar_client

    # Request that the file be sent.
    echo "ready:"

    # Receive the file.
    nc -l $port < /dev/null > $tar_client
}

# function: unpack_request
#
# Unpack the tar file received from the client and make the contents
# available for use when running 'stap'
function unpack_request {
    # Make a temp directory to work in.
    tmpdir_server=`mktemp -dt $tmpdir_prefix_server.XXXXXX` || \
	fatal "ERROR: cannot create temporary directory " $tmpdir_server
    tmpdir_env=`dirname $tmpdir_server`

    cd $tmpdir_server

    # Unpack the tar file.
    tar -xzf $tar_client || \
	fatal "ERROR: cannot unpack tar archive $tar_client"

    # Identify the client's request tree. The tar file should have expanded
    # into a single directory named to match $tmpdir_prefix_client.??????
    # which should now be the only item in the current directory.
    test "`ls | wc -l`" = 1 || \
	fatal "ERROR: Wrong number of files after expansion of client's tar file"

    tmpdir_client=`ls`
    tmpdir_client=`expr "$tmpdir_client" : "\\\($tmpdir_prefix_client\\\\.......\\\)"`

    test "X$tmpdir_client" != "X" || \
	fatal "ERROR: client tar file did not expand as expected"

    # Move the client's temp directory to a local temp location
    local local_tmpdir_client=`mktemp -dt $tmpdir_prefix_server.client.XXXXXX` || \
	fatal "ERROR: cannot create temporary tar file " $local_tmpdir_client
    mv $tmpdir_client/* $local_tmpdir_client
    rm -fr $tmpdir_client
    tmpdir_client=$local_tmpdir_client
}

# function: check_request
#
# Examine the contents of the request to make sure that they are valid.
function check_request {
    # Work in the temporary directory provided by the client
    cd $tmpdir_client

    # Add the necessary info from files in our temporary directory.
    cmdline=`read_data_file cmdline`
    test "X$cmdline" != "X" || exit 1
    client_sysinfo=`read_data_file sysinfo`
    test "X$client_sysinfo" != "X" || exit 1

    check_compatibility "$client_sysinfo" "`server_sysinfo`"
}

# function server_sysinfo
#
# Generate the server's sysinfo and echo it to stdout
function server_sysinfo {
    if test "X$sysinfo_server" = "X"; then
	# Add some info from uname
	sysinfo_server="`uname -rvm`"
    fi
    echo $sysinfo_server
}

# function check_compaibility SYSINFO1 SYSINFO2
#
# Make sure that systemtap as described by SYSINFO1 and SYSINFO2 are compaible
function check_compatibility {
    # TODO: This needs work
    # - Make sure the linux kernel matches exactly
    local sysinfo1=$1
    local sysinfo2=$2

    if test "$sysinfo1" != "$sysinfo2"; then
	error "ERROR: system configuration mismatch"
	error "  client: $sysinfo1"
	fatal "  server: $sysinfo2"
    fi
}

# function: read_data_file PREFIX
#
# Find a file whose name matches '$1.??????' whose first line
# contents are '$1: .*'. Read and echo the first line.
function read_data_file {
    for f in `ls $1.??????`
    do
	read < $f
	line=$REPLY
	data=`expr "$line" : "$1: \\\(.*\\\)"`
	if test "X$data" != "X"; then
	    echo $data
	    return
	fi
    done
    fatal "ERROR: Data file for $1 not found"
}

# function: parse_options [ STAP-OPTIONS ]
#
# Examine the command line. We need not do much checking, but we do need to
# parse all options in order to discover the ones we're interested in.
function parse_options {
    while test $# != 0
    do
	advance_p=0
	dash_seen=0

        # Start of a new token.
	first_token=$1
	until test $advance_p != 0
	do
            # Identify the next option
	    first_char=`expr "$first_token" : '\(.\).*'`
	    if test $dash_seen = 0; then
		if test "$first_char" = "-"; then
		    if test "$first_token" != "-"; then
	                # It's not a lone dash, so it's an option. Remove the dash.
			first_token=`expr "$first_token" : '-\(.*\)'`
			dash_seen=1
			first_char=`expr "$first_token" : '\(.\).*'`
		    fi
		fi
		if test $dash_seen = 0; then
	            # The dash has not been seen. This is either the script file
	            # name or an arument to be passed to the probe module.
	            # If this is the first time, and -e has not been specified,
	            # then it could be the name of the script file.
		    if test "X$e_script" = "X" -a "X$script_file" = "X"; then
			script_file=$first_token
		    fi
		    advance_p=$(($advance_p + 1))
		    break
		fi
	    fi
	    
            # We are at the start of an option. Look at the first character.
	    case $first_char in
		c)
		    get_arg $first_token "$2"
		    ;;
		D)
		    get_arg $first_token $2
		    ;;
		e)
		    get_arg $first_token "$2"
		    process_e "$stap_arg"
		    ;;
		I)
		    get_arg $first_token $2
		    ;;	
		k)
		    keep_temps=1
		    ;;
		l)
		    get_arg $first_token $2
		    ;;
		m)
		    get_arg $first_token $2
		    ;;
		o)
		    get_arg $first_token $2
		    ;;
		p)
		    get_arg $first_token $2
		    process_p $stap_arg
		    ;;
		r)
		    get_arg $first_token $2
		    ;;	
		R)
		    get_arg $first_token $2
		    ;;	
		s)
		    get_arg $first_token $2
		    ;;	
		x)
		    get_arg $first_token $2
		    ;;
		*)
		    # An unknown flag. Ignore it.
		    ;;
	    esac

	    if test $advance_p = 0; then
	        # Just another flag character. Consume it.
		first_token=`expr "$first_token" : '.\(.*\)'`
		if test "X$first_token" = "X"; then
		    advance_p=$(($advance_p + 1))
		fi
	    fi
	done

        # Consume the arguments we just processed.
	while test $advance_p != 0
	do
	    shift
	    advance_p=$(($advance_p - 1))
	done
    done
}

# function: get_arg FIRSTWORD SECONDWORD
#
# Collect an argument to the given option
function get_arg {
    # Remove first character. Advance to the next token, if the first one
    # is exhausted.
    local first=`expr "$1" : '.\(.*\)'`
    if test "X$first" = "X"; then
	shift
	advance_p=$(($advance_p + 1))
	first=$1
    fi

    stap_arg="$first"
    advance_p=$(($advance_p + 1))
}

# function: process_e ARGUMENT
#
# Process the -e flag.
function process_e {
    if test "X$e_script" = "X"; then
	e_script="$1"
	script_file=
    fi
}

# function: process_p ARGUMENT
#
# Process the -p flag.
function process_p {
    if test $1 -ge 1 -a $1 -le 5; then
	p_phase=$1
    fi
}

# function: call_stap
#
# Call 'stap' with the options provided. Don't run past phase 4.
function call_stap {
    # Invoke systemtap.
    # Use -k so we can return results to the client
    # Limit to -p4. i.e. don't run the module
    cd $tmpdir_client
    if test $p_phase -gt 4; then
	server_p_phase=4
    else
	server_p_phase=$p_phase
    fi
    eval stap $cmdline -k -p $server_p_phase \
	>>  $tmpdir_server/stdout \
	2>> $tmpdir_server/stderr
}

# function: create_response
#
# Add information to the server's temp directory representing the response
# to the client.
function create_response {
    cd $tmpdir_server

    # Get the name of the stap temp directory, which was kept, from stderr.
    tmpdir_line=`cat stderr | grep "Keeping temp"`
    tmpdir_stap=`expr "$tmpdir_line" : '.*"\(.*\)".*'`

    # Remove the message about keeping th<e stap temp directory from stderr, unless
    # the user did request to keep it.
    if test $keep_temps != 1; then
	sed -i "/^Keeping temp/d" stderr
    fi

    # If the user specified -p5, remove the name of the kernel module from stdout.
    if test $p_phase = 5; then
	sed -i '/\.ko$/d' stdout
    fi

    # Add the contents of the stap temp directory to the server output directory
    ln -s $tmpdir_stap `basename $tmpdir_stap`
}

# function: package_response
#
# Package the server's temp directory into a form suitable for sending to the
# client.
function package_response {
    cd $tmpdir_env
    # Create a place to generate our tar file of our temporary directory
    local tmpdir_server_base=`basename $tmpdir_server`
    tar_server=$tmpdir_env/`mktemp $tmpdir_server_base.tgz.XXXXXX` || \
	fatal "ERROR: cannot create temporary tar file " $tar_server
    chmod +r $tar_server

    # Generate the tar file
    tar -czhf $tar_server `basename $tmpdir_server` || \
	fatal "ERROR: tar of $tmpdir_server failed"
}

# function: send_response
#
# Notify the client that $tar_server is ready and wait for the client to take
# it.
# The protocol is:
#   server -> "done:"
#   server -> $tar_server
function send_response {
    echo "done:"
    # Now send it
    nc -l $port < $tar_server > /dev/null
}

# function: fatal [ MESSAGE ]
#
# Fatal error
# Prints its arguments to stderr and exits
function fatal {
    echo "$@" >&2
    cleanup
    exit 1
}

# Non fatal error
# Prints its arguments to stderr but does not exit
function error {
    echo "$@" >&2
}

# function cleanup
#
# Cleanup work files unless asked to keep them.
function cleanup {
    # Clean up.
    cd $tmpdir_env
    if test $keep_temps != 1; then
	rm -fr $tar_client
	rm -fr $tmpdir_client
	rm -fr $tar_server
	rm -fr $tmpdir_server
	rm -fr $tmpdir_stap
    fi
}

#-----------------------------------------------------------------------------
# Beginning of main line execution.
#-----------------------------------------------------------------------------
configuration "$@"
initialization
receive_request
unpack_request
check_request
eval parse_options $cmdline
call_stap
create_response
package_response
send_response 
cleanup

exit 0