import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class linker
{

	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);
		String filename = "^([A-Za-z0-9])+(.o:)$";
		String textSection = "^(\\s)*(U )([a-zA-Z0-9_]+)$";
		String dataSection = "^([0-9a-f]+) ([0-9a-f]+) ([TtbCdDU]) ([a-zA-Z0-9_]+)$";
		ArrayList<String> textArray = new ArrayList<String>();
		ArrayList<String[]> dataArray = new ArrayList<String[]>();
		HashMap<String, String> dataMap = new HashMap<String, String>();

		while(input.hasNextLine())
		{
			String line = input.nextLine();
			if (!line.equals(""))
			{
				if (line.matches(filename))
				{

				}
				else if (line.matches(textSection))
				{

					Pattern pattern = Pattern.compile(textSection);
					Matcher match = pattern.matcher(line);
					if (match.find())
					{
						textArray.add(match.group(3));
					}
				}
				else if (line.matches(dataSection))
				{
					Pattern pattern = Pattern.compile(dataSection);
					Matcher match = pattern.matcher(line);
					if (match.find())
					{
						String[] dataElement = new String[4];
						dataElement[0] = match.group(1);
						dataElement[1] = match.group(2);
						dataElement[2] = match.group(3);
						dataElement[3] = match.group(4);
						if (!dataMap.containsKey(dataElement[3]))
						{
							dataMap.put(dataElement[3], dataElement[2]);
						}
						else
						{
							if (dataMap.get(dataElement[3]).equals("C") && dataElement[2].toUpperCase().equals(dataElement[2]))
							{
								dataMap.put(dataElement[3], dataElement[2]);
							}
							else if (dataElement[2].equals("C") &&
									dataMap.get(dataElement[3]).toUpperCase().equals(dataMap.get(dataElement[3])))
							{
								continue;
							}
							else if (!dataMap.get(dataElement[3]).toUpperCase().equals(dataMap.get(dataElement[3])) &&
									dataElement[2].toUpperCase().equals(dataElement[2]))
							{
								dataMap.put(dataElement[3], dataElement[2]);
							}
							else if (dataMap.get(dataElement[3]).toUpperCase().equals(dataMap.get(dataElement[3])) &&
									dataElement[2].toUpperCase().equals(dataElement[2]))
							{
								System.out.println("Symbol " + dataElement[3] + " multiply defined");
								return;
							}
						}
						dataArray.add(dataElement);
					}
				}
				else
				{
					throw new IllegalArgumentException();
				}

				//System.out.println(line);
			}
		}
		Collections.sort(textArray);
		for (int i = 0; i < textArray.size(); i++)
		{
			if (dataMap.containsKey(textArray.get(i)))
			{
				textArray.remove(i);
				i--;
			}
		}
		for (String item: textArray)
		{
			System.out.println("                 U " + item);
		}
		int counter = 0x400680;
		for(String[] data: dataArray)
		{
			if (data[2].equalsIgnoreCase("t"))
			{
				System.out.print(String.format("%016x ", counter));
				System.out.print(String.format("%016x ", Integer.parseInt(data[1], 16)));
				System.out.print(data[2] + " ");
				System.out.println(data[3]);
				int i = Integer.parseInt(data[1], 16);
				if (((i / 4) * 4) != i)
				{
					i = ((i / 4) + 1) * 4;
				}
				counter += i;
			}
		}
		counter = 0x601044;
		for(String[] data: dataArray)
		{
			if (data[2].equalsIgnoreCase("d"))
			{
				System.out.print(String.format("%016x ", counter));
				System.out.print(String.format("%016x ", Integer.parseInt(data[1], 16)));
				System.out.print(data[2] + " ");
				System.out.println(data[3]);
				int i = Integer.parseInt(data[1], 16);
				if (((i / 4) * 4) != i)
				{
					i = ((i / 4) + 1) * 4;
				}
				counter += i;
			}
		}
		for(String[] data: dataArray)
		{
			if (data[2].equalsIgnoreCase("b"))
			{
				System.out.print(String.format("%016x ", counter));
				System.out.print(String.format("%016x ", Integer.parseInt(data[1], 16)));
				System.out.print(data[2] + " ");
				System.out.println(data[3]);
				int i = Integer.parseInt(data[1], 16);
				if (((i / 4) * 4) != i)
				{
					i = ((i / 4) + 1) * 4;
				}
				counter += i;
			}
			else if (data[2].equalsIgnoreCase("c") && dataMap.get(data[3]).equals("C"))
			{
				data[2] = "B";
				System.out.print(String.format("%016x ", counter));
				System.out.print(String.format("%016x ", Integer.parseInt(data[1], 16)));
				System.out.print(data[2] + " ");
				System.out.println(data[3]);
				int i = Integer.parseInt(data[1], 16);
				if (((i / 4) * 4) != i)
				{
					i = ((i / 4) + 1) * 4;
				}
				counter += i;
			}
		}
		input.close();
	}
}





2)
2. /home/ugrads/majors/ski23/Desktop/node-v9.5.0/out/Release/node
3. The -z flag takes a keyword that changes the way the linker treats the object. noexecstack is a keyword that tells the linker that it doesnt need an executable stack. src-> info ld
4. Using grep with " T " I found: ssl_cert_add1_chain_cert
5. I used grep and found that there are 502 strong global readonly symbols
6. Using size, I found that the size of the data section of the node executable is 101672
7.
a. /home/ugrads/majors/ski23/Desktop/node-v9.5.0/out/Release/obj.target/openssl/deps/openssl/openssl/ssl/bio_ssl.o
b. /home/ugrads/majors/ski23/Desktop/node-v9.5.0/out/Release/obj.target/nghttp2/deps/nghttp2/lib/nghttp2_session.o Is the module that contained an external reference to nghttp2_outbound_item.o. It referred to the symbol nghttp2_outbound_item_init

3)
1. ./pie uses different addresses for text, data, and bss between different iterations while ./no.pie uses the same addresses every time.
2. This helps prevent against return oriented programming attacks because it randomizes the addresses for the code every time.

4)
1. Running objdump -d lto2.o yields the following error: objdump: lto2.o: File format not recognized
2. Running file lto2.o yields: lto2.o: LLVM bitcode
3. define i64 @fac(i64) local_unnamed_addr #0 {
4.
00000000004004c0 <main>:
  4004c0:	b8 00 5f 37 00       	mov    $0x375f00,%eax
  4004c5:	c3                   	retq
  4004c6:	66 2e 0f 1f 84 00 00 	nopw   %cs:0x0(%rax,%rax,1)
  4004cd:	00 00 00
5. So cool...
Instead of actually calling the function fac, the compiler/linker just uses the value $0x375f00 and eliminates the function entirely