## Building the linux kernel from llvm bitcode requires writing scripts to copy, extract and recompile a lot of files in the right order. 
## A script is only valid for one configuration of the kernel

## The goal of this Python script is to automate the script building process for any configuration of the kernel.

## It takes one or more argument : the first argument is where to write the final script, and all the others are paths to files of which we should not use the bitcode.

import sys,os
import subprocess

# This is where most of the script gets written.
# This function takes as argument:
#    a list of path that should not be translated into bitcode
#    the depth from the root (this is a recursive function)
#    the path from the root to the current folder (its length should be depth)
def write_script(excluded_paths, depth, base_dir):
    builtin = open (base_dir+"arbi","w")
    subprocess.call(["ar", "-t", base_dir+"built-in.o"],stdout=builtin )
    builtin.close()
    builtin = open(base_dir+"arbi","r")
    out.writelines("mkdir -p $build_home/built-ins/"+base_dir+" \n")
    # In directories we store the list of depth 1 directories (and files) found in builtin
    directories=[]
    for line in builtin.readlines():
        line=line.split('\n')[0]
        words=line.split('/')
        if words[0]=="arch":    # We had to make an exception for the arch folder which does not have a built-in.o at the root.
            words[0]=words[0]+'/'+words[1]
            if words[2] in archbi:  #A second exception for arch, not all files in the folder are referenced in the arch/x86/built-in.o. We store the exceptions in the archi list
                words[0]=words[0]+'/'+words[2]
        if words[depth] not in directories and line not in standalone_objects: #Some objects are not listed in a built-in.o except at the root, so we include them separately in order not to mess the order of linking 
            directories.append(words[depth])

    # folders in which there are excluded folders which we will need to act on recursively
    excluded_roots = [path[depth] for path in excluded_paths] 

    for direc in directories:
        print base_dir+direc
        # the folder contains an excluded folder
        if direc in excluded_roots:
            # Check if we have an excluded folder
            if base_dir+direc in excluded_dirs:
                out.writelines("convert-thin-archive.sh "+base_dir+direc+"/built-in.o \n")
                out.writelines("cp "+ base_dir +direc+"/built-in.o.new $build_home/built-ins/"+base_dir+direc+"bi.o \n \n")
                link_args.writelines("built-ins/"+base_dir + direc +"bi.o ")
            # Else we filter the excluded_path list for only relevant stuff and we call the recursion on that folder
            else:
                relevant_excluded = [path for path in excluded_paths if (path[depth]==direc and len(path)>depth+1) ]
                if relevant_excluded:
                    write_script(relevant_excluded,depth+1,base_dir+direc+"/")
        else:
            #If the "directory" is a file, we copy it into the relevant objects folder and compile it
            if direc[-2:] == ".o":
                out.writelines("get-bc -b "+base_dir+direc+"\n")
                out.writelines("mkdir -p $build_home/built-ins/"+base_dir+"objects \n")
                out.writelines("cp "+ base_dir+direc+".bc $build_home/built-ins/"+base_dir+"objects \n")
                out.writelines("clang -c -no-integrated-as -mcmodel=kernel -o $build_home/built-ins/"+base_dir+ direc + " $build_home/built-ins/"+base_dir+"objects/" + direc+".bc \n \n")
                # We then add it to the linker arguments file
                link_args.writelines("built-ins/"+base_dir + direc +" ")
            # When dealing with a folder, we get the bitcode from the built-in.o file and check for errors in the log.
            # For each file that does not have a bitcode version (compiled straight from assembly) we copy it into the build folder directly and add it to the linker args
            else:
                if os.path.isfile("/vagrant/wrapper-logs/wrapper.log"):
                    os.rename("/vagrant/wrapper-logs/wrapper.log","/vagrant/wrapper-logs/before_"+direc.replace('/','_')+".log")
                path = base_dir + direc +"/built-in.o"
                subprocess.call(["get-bc", "-b", path ])
                subprocess.call(["touch","/vagrant/wrapper-logs/wrapper.log"])

                # Checking to see if any file failed to be extracted to bitcode
                llvm_log=open("/vagrant/wrapper-logs/wrapper.log","r")
                assembly_objects=[]
                for line in llvm_log.readlines():
                    if len(line)>=54 and line[:54]=="WARNING:Error reading the .llvm_bc section of ELF file":
                        assembly_objects.append(line[55:-2])
                llvm_log.close()

                # Deal with those files
                if assembly_objects:
                    out.writelines("mkdir -p $build_home/built-ins/" + base_dir +direc.replace('/','_')+"\n")
                for asf in assembly_objects:
                    out.writelines("cp "+ asf + " $build_home/built-ins/" + base_dir +direc.replace('/','_') +"\n")
                    filename= asf.split('/')[-1]
                    link_args.writelines("built-ins/"+base_dir + direc.replace('/','_') +'/'+filename+" ")
                # Deal with the rest
                if os.path.isfile(base_dir + direc +"/built-in.o.a.bc"):
                    out.writelines("cp "+ base_dir + direc +"/built-in.o.a.bc $build_home/built-ins/"+ base_dir + direc.replace('/','_') +"bi.o.bc \n")
                    out.writelines("clang -c -no-integrated-as -mcmodel=kernel -o $build_home/built-ins/"+ base_dir + direc.replace('/','_') + "bibc.o $build_home/built-ins/" + base_dir+direc.replace('/','_')+"bi.o.bc \n \n")
                    link_args.writelines("built-ins/"+base_dir + direc.replace('/','_') +"bibc.o ")

                builtin.close()


# excluded_dirs is a list where the folders excluded from bitcode translation will be stored
excluded_dirs=[]

if len(sys.argv) > 2:
    excluded_dirs=sys.argv[2:]

for path in excluded_dirs:
    if path[-1]=='/':
        path=path[:-1]

# Output file pathlib
build_dir= sys.argv[1]
if build_dir[-1]!='/':
    build_dir+='/'
#We transform excluded_dirs into a 2D array for better access to individual folders in the path
excluded=[path.split('/') for path in excluded_dirs]
out = open("build_script.sh","w+")
link_args = open(build_dir+"link-args","w+")
out.writelines("# Script written by the built-in-parsing.py script \n")
out.writelines("export build_home="+build_dir+"\n")

# List exceptions
standalone_objects = ["arch/x86/kernel/head_64.o","arch/x86/kernel/head64.o","arch/x86/kernel/ebda.o","arch/x86/kernel/platform-quirks.o"]#,"usr/initramfs_data.o"]
archbi=["lib","pci","video","power"]

# Calling the main function
write_script(excluded,0,"")

# Dealing with both lib files 
out.writelines("get-bc -b lib/lib.a \n ")
out.writelines("mkdir -p $build_home/lib\n")
out.writelines("cp lib/lib.a.bc $build_home/lib/ \n")
out.writelines("clang -c -no-integrated-as -mcmodel=kernel -o $build_home/lib/lib.a.o $build_home/lib/lib.a.bc \n")

if os.path.isfile("/vagrant/wrapper-logs/wrapper.log"):
    os.rename("/vagrant/wrapper-logs/wrapper.log","/vagrant/wrapper-logs/before_lib.log")
    #os.remove("./wrapper-logs/wrapper.log")
out.writelines("mkdir -p $build_home/arch/x86/lib/objects\n")
subprocess.call(["get-bc", "-b", "arch/x86/lib/lib.a" ])
subprocess.call(["touch","/vagrant/wrapper-logs/wrapper.log"])
llvm_log=open("/vagrant/wrapper-logs/wrapper.log","r")
assembly_objects=[]
for line in llvm_log.readlines():
    if len(line)>=55 and line[:54]=="WARNING:Error reading the .llvm_bc section of ELF file":
        assembly_objects.append(line[55:-2])
for asf in assembly_objects:
    out.writelines("cp "+ asf + " $build_home/arch/x86/lib/objects/ \n")
    filename= asf.split('/')[-1]
    #link_args.writelines("arch/x86/lib/objects/" +filename+" ") ##ignored to keep the order of linked files
 
out.writelines("cp arch/x86/lib/lib.a.bc $build_home/arch/x86/lib/lib.a.bc \n")
out.writelines("clang -c -no-integrated-as -mcmodel=kernel -o $build_home/arch/x86/lib/lib.a.o $build_home/arch/x86/lib/lib.a.bc \n \n")

#Deal with individual files 
out.writelines("cp arch/x86/kernel/vmlinux.lds $build_home \n")
out.writelines("cp .tmp_kallsyms2.o $build_home \n")
for sto in standalone_objects:
    out.writelines("cp --parents "+ sto+" $build_home \n")
out.writelines("\n#linking command \n")

out.writelines("cd $build_home \n")

# Final linking command
out.writelines("ld --build-id -T vmlinux.lds --whole-archive ")
for sto in standalone_objects:
    out.writelines(sto+" ")
out.writelines("@link-args ")
out.writelines("--no-whole-archive --start-group lib/lib.a.o arch/x86/lib/lib.a.o arch/x86/lib/objects/*  .tmp_kallsyms2.o --end-group -o vmlinux")