(*
    BSD 2-Clause License

    Copyright (c) 2019, Anton Krotov
    All rights reserved.
*)

MODULE ELF;

IMPORT BIN, WR := WRITER, CHL := CHUNKLISTS, LISTS;


CONST

    EI_NIDENT = 16;
    ET_EXEC = 2;
    ET_DYN = 3;

    EM_386 = 3;
    EM_8664 = 3EH;

    ELFCLASS32 = 1;
    ELFCLASS64 = 2;

    ELFDATA2LSB = 1;
    ELFDATA2MSB = 2;

    PF_X = 1;
    PF_W = 2;
    PF_R = 4;


TYPE

    Elf32_Ehdr = RECORD

        e_ident: ARRAY EI_NIDENT OF BYTE;

        e_type,
        e_machine: WCHAR;

        e_version,
        e_entry,
        e_phoff,
        e_shoff,
        e_flags: INTEGER;

        e_ehsize,
        e_phentsize,
        e_phnum,
        e_shentsize,
        e_shnum,
        e_shstrndx: WCHAR

    END;


    Elf32_Phdr = RECORD

        p_type,
        p_offset,
        p_vaddr,
        p_paddr,
        p_filesz,
        p_memsz,
        p_flags,
        p_align: INTEGER

    END;


    Elf32_Dyn = POINTER TO RECORD (LISTS.ITEM)

        d_tag, d_val: INTEGER

    END;


    Elf32_Sym = POINTER TO RECORD (LISTS.ITEM)

        name, value, size: INTEGER;
        info, other: CHAR;
        shndx: WCHAR

    END;


    FILE = WR.FILE;


VAR

    dynamic: LISTS.LIST;
    strtab:  CHL.BYTELIST;
    symtab:  LISTS.LIST;

    hashtab, bucket, chain: CHL.INTLIST;


PROCEDURE align (n, _align: INTEGER): INTEGER;
BEGIN
    IF n MOD _align # 0 THEN
        n := n + _align - (n MOD _align)
    END

    RETURN n
END align;


PROCEDURE Write16 (file: FILE; w: WCHAR);
BEGIN
    WR.Write16LE(file, ORD(w))
END Write16;


PROCEDURE WritePH (file: FILE; ph: Elf32_Phdr);
BEGIN
    WR.Write32LE(file, ph.p_type);
    WR.Write32LE(file, ph.p_offset);
    WR.Write32LE(file, ph.p_vaddr);
    WR.Write32LE(file, ph.p_paddr);
    WR.Write32LE(file, ph.p_filesz);
    WR.Write32LE(file, ph.p_memsz);
    WR.Write32LE(file, ph.p_flags);
    WR.Write32LE(file, ph.p_align)
END WritePH;


PROCEDURE WritePH64 (file: FILE; ph: Elf32_Phdr);
BEGIN
    WR.Write32LE(file, ph.p_type);
    WR.Write32LE(file, ph.p_flags);
    WR.Write64LE(file, ph.p_offset);
    WR.Write64LE(file, ph.p_vaddr);
    WR.Write64LE(file, ph.p_paddr);
    WR.Write64LE(file, ph.p_filesz);
    WR.Write64LE(file, ph.p_memsz);
    WR.Write64LE(file, ph.p_align)
END WritePH64;


PROCEDURE fixup (program: BIN.PROGRAM; text, data, bss: INTEGER; amd64: BOOLEAN);
VAR
    reloc: BIN.RELOC;
    L, delta: INTEGER;

BEGIN
    reloc := program.rel_list.first(BIN.RELOC);
    WHILE reloc # NIL DO

        L := BIN.get32le(program.code, reloc.offset);
        delta := 3 - reloc.offset - text - 7 * ORD(amd64);

        CASE reloc.opcode OF
        |BIN.PICDATA: BIN.put32le(program.code, reloc.offset, L + data + delta)
        |BIN.PICCODE: BIN.put32le(program.code, reloc.offset, BIN.GetLabel(program, L) + text + delta)
        |BIN.PICBSS:  BIN.put32le(program.code, reloc.offset, L + bss + delta)
        END;

        reloc := reloc.next(BIN.RELOC)
    END;
END fixup;


PROCEDURE NewDyn (tag, val: INTEGER);
VAR
    dyn: Elf32_Dyn;

BEGIN
    NEW(dyn);
    dyn.d_tag := tag;
    dyn.d_val := val;
    LISTS.push(dynamic, dyn)
END NewDyn;


PROCEDURE NewSym (name, value, size: INTEGER; info, other: CHAR; shndx: WCHAR);
VAR
    sym: Elf32_Sym;

BEGIN
    NEW(sym);
    sym.name := name;
    sym.value := value;
    sym.size := size;
    sym.info := info;
    sym.other := other;
    sym.shndx := shndx;

    LISTS.push(symtab, sym)
END NewSym;


PROCEDURE HashStr (name: ARRAY OF CHAR): INTEGER;
VAR
    i, h: INTEGER;
    g: SET;

BEGIN
    h := 0;
    i := 0;
    WHILE name[i] # 0X DO
        h := h * 16 + ORD(name[i]);
        g := BITS(h) * {28..31};
        h := ORD(BITS(h) / BITS(LSR(ORD(g), 24)) - g);
        INC(i)
    END

    RETURN h
END HashStr;


PROCEDURE MakeHash (bucket, chain: CHL.INTLIST; symCount: INTEGER);
VAR
    symi, hi, k: INTEGER;

BEGIN
    FOR symi := 0 TO symCount - 1 DO
        CHL.SetInt(chain, symi, 0);
        hi := CHL.GetInt(hashtab, symi) MOD symCount;
        IF CHL.GetInt(bucket, hi) # 0 THEN
            k := symi;
            WHILE CHL.GetInt(chain, k) # 0 DO
                k := CHL.GetInt(chain, k)
            END;
            CHL.SetInt(chain, k, CHL.GetInt(bucket, hi))
        END;
        CHL.SetInt(bucket, hi, symi)
    END
END MakeHash;


PROCEDURE write* (program: BIN.PROGRAM; FileName: ARRAY OF CHAR; fini: INTEGER; so, amd64: BOOLEAN);
CONST
    interp  =  0;
    dyn     =  1;
    header  =  2;
    text    =  3;
    data    =  4;
    bss     =  5;

    linuxInterpreter64 = "/lib64/ld-linux-x86-64.so.2";
    linuxInterpreter32 = "/lib/ld-linux.so.2";

    exeBaseAddress32 = 8048000H;
    exeBaseAddress64 = 400000H;
    dllBaseAddress = 0;

    DT_NULL = 0;
    DT_NEEDED = 1;
    DT_HASH = 4;
    DT_STRTAB = 5;
    DT_SYMTAB = 6;
    DT_RELA = 7;
    DT_RELASZ = 8;
    DT_RELAENT = 9;
    DT_STRSZ = 10;
    DT_SYMENT = 11;
    DT_INIT = 12;
    DT_FINI = 13;
    DT_SONAME = 14;
    DT_REL = 17;
    DT_RELSZ = 18;
    DT_RELENT = 19;

VAR
    ehdr: Elf32_Ehdr;
    phdr: ARRAY 16 OF Elf32_Phdr;

    i, BaseAdr, offset, pad, VA, symCount: INTEGER;

    SizeOf: RECORD header, code, data, bss: INTEGER END;

    Offset: RECORD symtab, reltab, hash, strtab, dyn: INTEGER END;

    File: FILE;

    Interpreter: ARRAY 40 OF CHAR; lenInterpreter: INTEGER;

    item: LISTS.ITEM;

    Name: ARRAY 2048 OF CHAR;

BEGIN
    dynamic := LISTS.create(NIL);
    symtab  := LISTS.create(NIL);
    strtab  := CHL.CreateByteList();

    IF amd64 THEN
        BaseAdr := exeBaseAddress64;
        Interpreter := linuxInterpreter64
    ELSE
        BaseAdr := exeBaseAddress32;
        Interpreter := linuxInterpreter32
    END;

    IF so THEN
        BaseAdr := dllBaseAddress
    END;

    lenInterpreter := LENGTH(Interpreter) + 1;

    SizeOf.code := CHL.Length(program.code);
    SizeOf.data := CHL.Length(program.data);
    SizeOf.bss  := program.bss;

    ehdr.e_ident[0] := 7FH;
    ehdr.e_ident[1] := ORD("E");
    ehdr.e_ident[2] := ORD("L");
    ehdr.e_ident[3] := ORD("F");
    IF amd64 THEN
        ehdr.e_ident[4] := ELFCLASS64
    ELSE
        ehdr.e_ident[4] := ELFCLASS32
    END;
    ehdr.e_ident[5] := ELFDATA2LSB;
    ehdr.e_ident[6] := 1;
    ehdr.e_ident[7] := 3;
    FOR i := 8 TO EI_NIDENT - 1 DO
        ehdr.e_ident[i] := 0
    END;

    IF so THEN
        ehdr.e_type := WCHR(ET_DYN)
    ELSE
        ehdr.e_type := WCHR(ET_EXEC)
    END;

    ehdr.e_version := 1;
    ehdr.e_shoff := 0;
    ehdr.e_flags := 0;
    ehdr.e_shnum := WCHR(0);
    ehdr.e_shstrndx := WCHR(0);
    ehdr.e_phnum := WCHR(6);

    IF amd64 THEN
        ehdr.e_machine := WCHR(EM_8664);
        ehdr.e_phoff := 40H;
        ehdr.e_ehsize := WCHR(40H);
        ehdr.e_phentsize := WCHR(38H);
        ehdr.e_shentsize := WCHR(40H)
    ELSE
        ehdr.e_machine := WCHR(EM_386);
        ehdr.e_phoff := 34H;
        ehdr.e_ehsize := WCHR(34H);
        ehdr.e_phentsize := WCHR(20H);
        ehdr.e_shentsize := WCHR(28H)
    END;

    SizeOf.header := ORD(ehdr.e_ehsize) + ORD(ehdr.e_phentsize) * ORD(ehdr.e_phnum);

    phdr[interp].p_type := 3;
    phdr[interp].p_offset := SizeOf.header;
    phdr[interp].p_vaddr := BaseAdr + phdr[interp].p_offset;
    phdr[interp].p_paddr := phdr[interp].p_vaddr;
    phdr[interp].p_filesz := lenInterpreter;
    phdr[interp].p_memsz := lenInterpreter;
    phdr[interp].p_flags := PF_R;
    phdr[interp].p_align := 1;

    phdr[dyn].p_type := 2;
    phdr[dyn].p_offset := phdr[interp].p_offset + phdr[interp].p_filesz;
    phdr[dyn].p_vaddr := BaseAdr + phdr[dyn].p_offset;
    phdr[dyn].p_paddr := phdr[dyn].p_vaddr;

    hashtab := CHL.CreateIntList();

    CHL.PushInt(hashtab, HashStr(""));
    NewSym(CHL.PushStr(strtab, ""), 0, 0, 0X, 0X, 0X);
    CHL.PushInt(hashtab, HashStr("dlopen"));
    NewSym(CHL.PushStr(strtab, "dlopen"), 0, 0, 12X, 0X, 0X);
    CHL.PushInt(hashtab, HashStr("dlsym"));
    NewSym(CHL.PushStr(strtab, "dlsym"), 0, 0, 12X, 0X, 0X);

    IF so THEN
        item := program.exp_list.first;
        WHILE item # NIL DO
            ASSERT(CHL.GetStr(program.export, item(BIN.EXPRT).nameoffs, Name));
            CHL.PushInt(hashtab, HashStr(Name));
            NewSym(CHL.PushStr(strtab, Name), item(BIN.EXPRT).label, 0, 12X, 0X, 0X);
            item := item.next
        END;
        ASSERT(CHL.GetStr(program.data, program.modname, Name))
    END;

    symCount := LISTS.count(symtab);

    bucket  := CHL.CreateIntList();
    chain   := CHL.CreateIntList();

    FOR i := 1 TO symCount DO
        CHL.PushInt(bucket, 0);
        CHL.PushInt(chain, 0)
    END;

    MakeHash(bucket, chain, symCount);

    NewDyn(DT_NEEDED, CHL.PushStr(strtab, "libdl.so.2"));
    NewDyn(DT_STRTAB, 0);
    NewDyn(DT_STRSZ, CHL.Length(strtab));
    NewDyn(DT_SYMTAB, 0);

    IF amd64 THEN
        NewDyn(DT_SYMENT, 24);
        NewDyn(DT_RELA, 0);
        NewDyn(DT_RELASZ, 48);
        NewDyn(DT_RELAENT, 24)
    ELSE
        NewDyn(DT_SYMENT, 16);
        NewDyn(DT_REL, 0);
        NewDyn(DT_RELSZ, 16);
        NewDyn(DT_RELENT, 8)
    END;

    NewDyn(DT_HASH, 0);

    IF so THEN
        NewDyn(DT_SONAME, CHL.PushStr(strtab, Name));
        NewDyn(DT_INIT, 0);
        NewDyn(DT_FINI, 0)
    END;

    NewDyn(DT_NULL, 0);

    Offset.symtab := LISTS.count(dynamic) * (8 + 8 * ORD(amd64));
    Offset.reltab := Offset.symtab + symCount * (16 + 8 * ORD(amd64));
    Offset.hash   := Offset.reltab + (8 + 16 * ORD(amd64)) * 2;
    Offset.strtab := Offset.hash + (symCount * 2 + 2) * 4;

    Offset.dyn := phdr[dyn].p_offset;

    item := LISTS.getidx(dynamic, 1); item(Elf32_Dyn).d_val := Offset.strtab + Offset.dyn + BaseAdr;
    item := LISTS.getidx(dynamic, 3); item(Elf32_Dyn).d_val := Offset.symtab + Offset.dyn + BaseAdr;
    item := LISTS.getidx(dynamic, 5); item(Elf32_Dyn).d_val := Offset.reltab + Offset.dyn + BaseAdr;
    item := LISTS.getidx(dynamic, 8); item(Elf32_Dyn).d_val := Offset.hash   + Offset.dyn + BaseAdr;

    phdr[dyn].p_filesz := Offset.strtab + CHL.Length(strtab) + 8 + 8 * ORD(amd64);
    phdr[dyn].p_memsz  := phdr[dyn].p_filesz;

    phdr[dyn].p_flags := PF_R;
    phdr[dyn].p_align := 1;

    offset := 0;

    phdr[header].p_type := 1;
    phdr[header].p_offset := offset;
    phdr[header].p_vaddr := BaseAdr;
    phdr[header].p_paddr := BaseAdr;
    phdr[header].p_filesz := 244 + 156 * ORD(amd64) + lenInterpreter + phdr[dyn].p_filesz;
    phdr[header].p_memsz  := phdr[header].p_filesz;
    phdr[header].p_flags := PF_R + PF_W;
    phdr[header].p_align := 1000H;

    offset := offset + phdr[header].p_filesz;
    VA := BaseAdr + offset + 1000H;

    phdr[text].p_type := 1;
    phdr[text].p_offset := offset;
    phdr[text].p_vaddr := VA;
    phdr[text].p_paddr := VA;
    phdr[text].p_filesz := SizeOf.code;
    phdr[text].p_memsz := SizeOf.code;
    phdr[text].p_flags := PF_X + PF_R;
    phdr[text].p_align := 1000H;

    ehdr.e_entry := phdr[text].p_vaddr;

    offset := offset + phdr[text].p_filesz;
    VA := BaseAdr + offset + 2000H;
    pad := (16 - VA MOD 16) MOD 16;

    phdr[data].p_type := 1;
    phdr[data].p_offset := offset;
    phdr[data].p_vaddr := VA;
    phdr[data].p_paddr := VA;
    phdr[data].p_filesz := SizeOf.data + pad;
    phdr[data].p_memsz := SizeOf.data + pad;
    phdr[data].p_flags := PF_R + PF_W;
    phdr[data].p_align := 1000H;

    offset := offset + phdr[data].p_filesz;
    VA := BaseAdr + offset + 3000H;

    phdr[bss].p_type := 1;
    phdr[bss].p_offset := offset;
    phdr[bss].p_vaddr := VA;
    phdr[bss].p_paddr := VA;
    phdr[bss].p_filesz := 0;
    phdr[bss].p_memsz := SizeOf.bss + 16;
    phdr[bss].p_flags := PF_R + PF_W;
    phdr[bss].p_align := 1000H;

    fixup(program, ehdr.e_entry, phdr[data].p_vaddr + pad, align(phdr[bss].p_vaddr, 16), amd64);

    item := symtab.first;
    WHILE item # NIL DO
        IF item(Elf32_Sym).value # 0 THEN
            INC(item(Elf32_Sym).value, ehdr.e_entry)
        END;
        item := item.next
    END;

    IF so THEN
        item := LISTS.getidx(dynamic, 10); item(Elf32_Dyn).d_val := ehdr.e_entry;
        item := LISTS.getidx(dynamic, 11); item(Elf32_Dyn).d_val := BIN.GetLabel(program, fini) + ehdr.e_entry
    END;

    File := WR.Create(FileName);

    FOR i := 0 TO EI_NIDENT - 1 DO
        WR.WriteByte(File, ehdr.e_ident[i])
    END;

    Write16(File, ehdr.e_type);
    Write16(File, ehdr.e_machine);

    WR.Write32LE(File, ehdr.e_version);
    IF amd64 THEN
        WR.Write64LE(File, ehdr.e_entry);
        WR.Write64LE(File, ehdr.e_phoff);
        WR.Write64LE(File, ehdr.e_shoff)
    ELSE
        WR.Write32LE(File, ehdr.e_entry);
        WR.Write32LE(File, ehdr.e_phoff);
        WR.Write32LE(File, ehdr.e_shoff)
    END;
    WR.Write32LE(File, ehdr.e_flags);

    Write16(File, ehdr.e_ehsize);
    Write16(File, ehdr.e_phentsize);
    Write16(File, ehdr.e_phnum);
    Write16(File, ehdr.e_shentsize);
    Write16(File, ehdr.e_shnum);
    Write16(File, ehdr.e_shstrndx);

    IF amd64 THEN
        WritePH64(File, phdr[interp]);
        WritePH64(File, phdr[dyn]);
        WritePH64(File, phdr[header]);
        WritePH64(File, phdr[text]);
        WritePH64(File, phdr[data]);
        WritePH64(File, phdr[bss])
    ELSE
        WritePH(File, phdr[interp]);
        WritePH(File, phdr[dyn]);
        WritePH(File, phdr[header]);
        WritePH(File, phdr[text]);
        WritePH(File, phdr[data]);
        WritePH(File, phdr[bss])
    END;

    FOR i := 0 TO lenInterpreter - 1 DO
        WR.WriteByte(File, ORD(Interpreter[i]))
    END;

    i := 0;
    IF amd64 THEN
        item := dynamic.first;
        WHILE item # NIL DO
            WR.Write64LE(File, item(Elf32_Dyn).d_tag);
            WR.Write64LE(File, item(Elf32_Dyn).d_val);
            item := item.next
        END;

        item := symtab.first;
        WHILE item # NIL DO
            WR.Write32LE(File, item(Elf32_Sym).name);
            WR.WriteByte(File, ORD(item(Elf32_Sym).info));
            WR.WriteByte(File, ORD(item(Elf32_Sym).other));
            Write16(File, item(Elf32_Sym).shndx);
            WR.Write64LE(File, item(Elf32_Sym).value);
            WR.Write64LE(File, item(Elf32_Sym).size);
            item := item.next
        END;

        WR.Write64LE(File, phdr[dyn].p_filesz + Offset.dyn + BaseAdr - 16);
        WR.Write32LE(File, 1);
        WR.Write32LE(File, 1);
        WR.Write64LE(File, 0);
        WR.Write64LE(File, phdr[dyn].p_filesz + Offset.dyn + BaseAdr - 8);
        WR.Write32LE(File, 1);
        WR.Write32LE(File, 2);
        WR.Write64LE(File, 0);

        WR.Write32LE(File, symCount);
        WR.Write32LE(File, symCount);

        FOR i := 0 TO symCount - 1 DO
            WR.Write32LE(File, CHL.GetInt(bucket, i))
        END;

        FOR i := 0 TO symCount - 1 DO
            WR.Write32LE(File, CHL.GetInt(chain, i))
        END;

        CHL.WriteToFile(File, strtab);
        WR.Write64LE(File, 0);
        WR.Write64LE(File, 0)

    ELSE
        item := dynamic.first;
        WHILE item # NIL DO
            WR.Write32LE(File, item(Elf32_Dyn).d_tag);
            WR.Write32LE(File, item(Elf32_Dyn).d_val);
            item := item.next
        END;

        item := symtab.first;
        WHILE item # NIL DO
            WR.Write32LE(File, item(Elf32_Sym).name);
            WR.Write32LE(File, item(Elf32_Sym).value);
            WR.Write32LE(File, item(Elf32_Sym).size);
            WR.WriteByte(File, ORD(item(Elf32_Sym).info));
            WR.WriteByte(File, ORD(item(Elf32_Sym).other));
            Write16(File, item(Elf32_Sym).shndx);
            item := item.next
        END;

        WR.Write32LE(File, phdr[dyn].p_filesz + Offset.dyn + BaseAdr - 8);
        WR.Write32LE(File, 00000101H);
        WR.Write32LE(File, phdr[dyn].p_filesz + Offset.dyn + BaseAdr - 4);
        WR.Write32LE(File, 00000201H);

        WR.Write32LE(File, symCount);
        WR.Write32LE(File, symCount);

        FOR i := 0 TO symCount - 1 DO
            WR.Write32LE(File, CHL.GetInt(bucket, i))
        END;

        FOR i := 0 TO symCount - 1 DO
            WR.Write32LE(File, CHL.GetInt(chain, i))
        END;

        CHL.WriteToFile(File, strtab);
        WR.Write32LE(File, 0);
        WR.Write32LE(File, 0)

    END;

    CHL.WriteToFile(File, program.code);
    WHILE pad > 0 DO
        WR.WriteByte(File, 0);
        DEC(pad)
    END;
    CHL.WriteToFile(File, program.data);
    WR.Close(File)
END write;


END ELF.