(*
    BSD 2-Clause License

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

MODULE ELF;

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


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;

    FILE = WR.FILE;


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

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

    i, LoadAdr, offset, pad, VA: INTEGER;

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

    File: FILE;

    str: ARRAY 40 OF CHAR; lstr: INTEGER;
    Dyn: ARRAY 350 OF BYTE;

BEGIN
    IF amd64 THEN
        str := "/lib64/ld-linux-x86-64.so.2"
    ELSE
        str := "/lib/ld-linux.so.2"
    END;
    lstr := LENGTH(str);

    IF amd64 THEN
        LoadAdr := 400000H
    ELSE
        LoadAdr := 08048000H
    END;

    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;

    ehdr.e_type := WCHR(ET_EXEC);
    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 := LoadAdr + phdr[interp].p_offset;
    phdr[interp].p_paddr := LoadAdr + phdr[interp].p_offset;
    phdr[interp].p_filesz := lstr + 1;
    phdr[interp].p_memsz := lstr + 1;
    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 := LoadAdr + phdr[dyn].p_offset;
    phdr[dyn].p_paddr := LoadAdr + phdr[dyn].p_offset;
    IF amd64 THEN
        phdr[dyn].p_filesz := 0A0H;
        phdr[dyn].p_memsz  := 0A0H
    ELSE
        phdr[dyn].p_filesz := 50H;
        phdr[dyn].p_memsz  := 50H
    END;
    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 := LoadAdr;
    phdr[header].p_paddr := LoadAdr;
    IF amd64 THEN
        phdr[header].p_filesz := 305H;
        phdr[header].p_memsz  := 305H
    ELSE
        phdr[header].p_filesz := 1D0H;
        phdr[header].p_memsz  := 1D0H
    END;
    phdr[header].p_flags := PF_R + PF_W;
    phdr[header].p_align := 1000H;
    
    offset := offset + phdr[header].p_filesz;
    VA := LoadAdr + 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 := LoadAdr + 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 := LoadAdr + 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, phdr[text].p_vaddr, phdr[data].p_vaddr + pad, align(phdr[bss].p_vaddr, 16), amd64);

    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 lstr DO
        WR.WriteByte(File, ORD(str[i]))
    END;

    i := 0;
    IF amd64 THEN
        BIN.InitArray(Dyn, i, "01000000000000000E000000000000000500000000000000DC02400000000000");
        BIN.InitArray(Dyn, i, "0A00000000000000190000000000000006000000000000004C02400000000000");
        BIN.InitArray(Dyn, i, "0B00000000000000180000000000000007000000000000009402400000000000");
        BIN.InitArray(Dyn, i, "0800000000000000300000000000000009000000000000001800000000000000");
        BIN.InitArray(Dyn, i, "0400000000000000C40240000000000000000000000000000000000000000000");
        BIN.InitArray(Dyn, i, "0000000000000000000000000000000000000000000000000100000012000000");
        BIN.InitArray(Dyn, i, "0000000000000000000000000000000008000000120000000000000000000000");
        BIN.InitArray(Dyn, i, "0000000000000000F50240000000000001000000010000000000000000000000");
        BIN.InitArray(Dyn, i, "FD02400000000000010000000200000000000000000000000100000003000000");
        BIN.InitArray(Dyn, i, "0000000001000000020000000000000000646C6F70656E00646C73796D006C69");
        BIN.InitArray(Dyn, i, "62646C2E736F2E320000000000000000000000000000000000")
    ELSE
        BIN.InitArray(Dyn, i, "010000000E00000005000000AF8104080A000000190000000600000057810408");
        BIN.InitArray(Dyn, i, "0B00000010000000110000008781040812000000100000001300000008000000");
        BIN.InitArray(Dyn, i, "0400000097810408000000000000000000000000000000000000000000000000");
        BIN.InitArray(Dyn, i, "0100000000000000000000001200000008000000000000000000000012000000");
        BIN.InitArray(Dyn, i, "C881040801010000CC8104080102000001000000030000000000000001000000");
        BIN.InitArray(Dyn, i, "020000000000000000646C6F70656E00646C73796D006C6962646C2E736F2E32");
        BIN.InitArray(Dyn, i, "000000000000000000")
    END;

    WR.Write(File, Dyn, i);

    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.