static internal void RegisterSection(string name, string flags, string type, string flag_specific_arguments)
{
if (sections.ContainsKey(name))
return;
GetKnownSectionType(name, ref flags, ref type, ref flag_specific_arguments);
Section s = new Section();
s.name = name;
if (flags == null)
flags = "";
if (type == null)
type = "";
if (flag_specific_arguments == null)
flag_specific_arguments = "";
// Default if flags is null is for not loaded or writeable
if (flags == "")
{
s.Alloc = false;
s.Write = false;
s.Exec = false;
}
foreach(char c in flags)
{
switch(c)
{
case 'a':
s.Alloc = true;
break;
case 'w':
s.Write = true;
s.Alloc = true;
break;
case 'x':
s.Exec = true;
s.Alloc = true;
break;
}
}
// Default type is data (ProgBits)
s.SectionType = Section.SectType.ProgBits;
if (type == "progbits")
s.SectionType = Section.SectType.ProgBits;
else if (type == "nobits")
s.SectionType = Section.SectType.NoBits;
else if (type == "note")
s.SectionType = Section.SectType.Note;
else
s.SectionType = Section.SectType.Unknown;
sections[s.name] = s;
}
internal MakeState(Dictionary<string, LabelOffset> label_offsets, Section cur_sect)
{ lo = label_offsets; cs = cur_sect; }
private static int AllocateString(string name, Section strtab)
{
if (strtab.StringCache == null)
strtab.StringCache = new Dictionary<string, int>();
else if (strtab.StringCache.ContainsKey(name))
return strtab.StringCache[name];
if(strtab.cur_offset == 0)
{
strtab.oput.Add(0);
strtab.cur_offset++;
}
int ret = strtab.cur_offset;
foreach(char c in name)
{
strtab.oput.Add((byte)c);
strtab.cur_offset++;
}
strtab.oput.Add(0);
strtab.cur_offset++;
strtab.StringCache[name] = ret;
return ret;
}
private static Expression EvaluateOperand(Expression src, Dictionary<string, LabelOffset> label_offsets,
Section cur_section)
{
if (src == null)
return null;
MakeState s = new MakeState(label_offsets, cur_section);
// ExpandComplex already uses operands
if (src is Operand)
return src;
var v = src.Evaluate(s);
switch(v.Type)
{
case Expression.EvalResult.ResultType.Register:
return new RegisterOperand { val = v.strval };
case Expression.EvalResult.ResultType.Int:
return new IntegerOperand { val = v.intval };
case Expression.EvalResult.ResultType.Relocation:
return v.relocval;
default:
throw new NotImplementedException();
}
}
static internal void GenerateELF(System.IO.BinaryWriter w)
{
/* First, build the section table. We only include those
sections that have some data defined.
Section 0 is the null section. We also include sections for
the string and symbol tables
*/
MakeState ms = new MakeState(Program.los, null);
List<Section> sects = new List<Section>();
sects.Add(null);
int cur_sect = 1;
foreach(var s in Program.sections)
{
if (s.Value.cur_offset == 0)
continue;
if (s.Value.SectionType == Section.SectType.Unknown)
continue;
s.Value.SectionIdx = cur_sect++;
sects.Add(s.Value);
Section s_reloc = new Section();
foreach(var r in Program.relocs)
{
if(r.SourceSection == s.Value)
s_reloc.relocs.Add(r);
}
if(s_reloc.relocs.Count > 0)
{
s_reloc.name = s.Value.name + ".rela";
s_reloc.SectionType = Section.SectType.Rela;
s_reloc.SectionIdx = cur_sect++;
s.Value.RelocSectionIdx = s_reloc.SectionIdx;
s_reloc.RelocSectionIdx = s.Value.SectionIdx;
sects.Add(s_reloc);
}
}
// Add symbol, symbol string and section header string tables
Section symtab = new Section();
symtab.name = ".symtab";
symtab.SectionIdx = cur_sect++;
symtab.SectionType = Section.SectType.SymTab;
sects.Add(symtab);
Section strtab = new Section();
strtab.name = ".strtab";
strtab.SectionIdx = cur_sect++;
strtab.SectionType = Section.SectType.StrTab;
sects.Add(strtab);
Section shstrtab = new Section();
shstrtab.name = ".shstrtab";
shstrtab.SectionIdx = cur_sect++;
shstrtab.SectionType = Section.SectType.StrTab;
sects.Add(shstrtab);
// Add strings to section string table
foreach(Section s in sects)
{
if (s == null)
continue;
s.ShStrNdx = AllocateString(s.name, shstrtab);
}
// Build symbol table
Dictionary<string, Symbol> syms = new Dictionary<string, Symbol>();
foreach(var v in Program.los)
{
Symbol newsym = new Symbol();
newsym.name = v.Key;
newsym.StrNdx = AllocateString(newsym.name, strtab);
newsym.Section = v.Value.Section;
newsym.Offset = v.Value.Offset;
if(Program.comm_objs.ContainsKey(newsym.name))
{
newsym.IsCommon = true;
newsym.Offset = Program.comm_objs[newsym.name].Align.Evaluate(ms).AsInt;
newsym.Size = Program.comm_objs[newsym.name].Size.Evaluate(ms).AsInt;
}
if(Program.obj_sizes.ContainsKey(newsym.name))
{
newsym.Size = Program.obj_sizes[newsym.name].Evaluate(ms).AsInt;
}
if(Program.obj_types.ContainsKey(newsym.name))
{
string t = Program.obj_types[newsym.name];
if (t == "function")
newsym.Type = 2;
else if (t == "object")
newsym.Type = 1;
}
if(Program.global_objs.ContainsKey(newsym.name))
{
newsym.IsGlobal = true;
}
syms[newsym.name] = newsym;
}
foreach(var v in Program.comm_objs)
{
if (syms.ContainsKey(v.Key))
continue;
Symbol newsym = new Symbol();
newsym.name = v.Key;
newsym.StrNdx = AllocateString(newsym.name, strtab);
newsym.IsCommon = true;
if(Program.global_objs.ContainsKey(newsym.name))
newsym.IsGlobal = true;
if (Program.obj_types.ContainsKey(newsym.name))
{
string t = Program.obj_types[newsym.name];
if (t == "function")
newsym.Type = 2;
else if (t == "object")
newsym.Type = 1;
}
newsym.Size = Program.comm_objs[newsym.name].Size.Evaluate(ms).AsInt;
newsym.Offset = Program.comm_objs[newsym.name].Align.Evaluate(ms).AsInt;
syms[newsym.name] = newsym;
}
foreach(var v in Program.relocs)
{
if (syms.ContainsKey(v.TargetName))
continue;
Symbol newsym = new Symbol();
newsym.name = v.TargetName;
newsym.StrNdx = AllocateString(newsym.name, strtab);
newsym.IsGlobal = true;
newsym.Section = null;
syms[newsym.name] = newsym;
}
// Symbols start with a null symbol, then all local symbols,
// then global ones.
List<Symbol> sym_list = new List<Symbol>();
sym_list.Add(null);
// Add symbols for each section
foreach(Section s in sects)
{
if (s == null)
continue;
Symbol sect_sym = new Symbol();
sect_sym.name = s.name;
sect_sym.StrNdx = AllocateString(sect_sym.name, strtab);
sect_sym.Index = sym_list.Count;
sect_sym.Type = 3;
sect_sym.Section = s;
sect_sym.Offset = 0;
sect_sym.Size = s.oput.Count;
sym_list.Add(sect_sym);
}
// Now iterate through looking for local symbols
foreach(var v in syms)
{
if (v.Value.IsGlobal)
continue;
v.Value.Index = sym_list.Count();
sym_list.Add(v.Value);
}
int max_local = sym_list.Count();
// Now add global symbols
foreach(var v in syms)
{
if (!v.Value.IsGlobal)
continue;
v.Value.Index = sym_list.Count();
sym_list.Add(v.Value);
}
// Extract a list of symbol indices
Dictionary<string, int> sym_idx = new Dictionary<string, int>();
foreach(var v in sym_list)
{
if (v == null)
continue;
sym_idx[v.name] = v.Index;
}
// Begin writing out the elf file header
w.Write((byte)0x7f);
w.Write((byte)'E');
w.Write((byte)'L');
w.Write((byte)'F');
w.Write((byte)1);
w.Write((byte)1);
w.Write((byte)1);
for (int i = 0; i < 9; i++)
w.Write((byte)0);
w.Write((ushort)1); // relocatable
w.Write((byte)'J'); // Machine type 'J', 'C'
w.Write((byte)'C');
w.Write((uint)1); // version
w.Write((uint)0); // e_entry
w.Write((uint)0); // e_phoff
long e_shoff_offset = w.BaseStream.Position;
w.Write((uint)0); // e_shoff
w.Write((uint)0); // e_flags
w.Write((ushort)52); // e_ehsize
w.Write((ushort)0); // e_phentsize
w.Write((ushort)0); // e_phnum
w.Write((ushort)40); // e_shentsize
w.Write((ushort)cur_sect); // e_shnum
w.Write((ushort)shstrtab.SectionIdx); // e_shstrndx
// Now write out the section data
foreach(Section s in sects)
{
if (s == null)
continue;
// align up to a multiple of 16
while ((w.BaseStream.Position & 0xf) != 0)
w.Write((byte)0);
switch(s.SectionType)
{
case Section.SectType.NoBits:
s.SectionSize = s.cur_offset;
break;
case Section.SectType.ProgBits:
case Section.SectType.Note:
case Section.SectType.StrTab:
s.FileOffset = (int)w.BaseStream.Position;
foreach (byte b in s.oput)
w.Write(b);
s.SectionSize = (int)w.BaseStream.Position - s.FileOffset;
break;
case Section.SectType.SymTab:
s.FileOffset = (int)w.BaseStream.Position;
foreach(var sym in sym_list)
{
if(sym == null)
{
w.Write((uint)0);
w.Write((uint)0);
w.Write((uint)0);
w.Write((uint)0);
}
else
{
w.Write(sym.StrNdx);
w.Write(sym.Offset);
w.Write(sym.Size);
uint st_info = 0;
if (sym.IsWeak)
st_info |= 0x20;
else if (sym.IsGlobal)
st_info |= 0x10;
st_info |= (uint)sym.Type;
w.Write((byte)st_info);
w.Write((byte)0);
if (sym.IsCommon)
w.Write((ushort)0xfff2);
else if (sym.Section == null)
w.Write((ushort)0x0);
else
w.Write((ushort)sym.Section.SectionIdx);
}
}
s.SectionSize = (int)w.BaseStream.Position - s.FileOffset;
break;
case Section.SectType.Rela:
s.FileOffset = (int)w.BaseStream.Position;
foreach(var r in s.relocs)
{
if (r == null)
{
w.Write((uint)0);
w.Write((uint)0);
w.Write((uint)0);
}
else
{
w.Write(r.SourceOffset);
uint sym_tab_idx = (uint)sym_idx[r.TargetName];
uint r_info = sym_tab_idx << 8;
r_info |= (uint)r.Type;
w.Write(r_info);
w.Write(r.Addend);
}
}
s.SectionSize = (int)w.BaseStream.Position - s.FileOffset;
break;
}
}
// Align up to a multiple of 16
while ((w.BaseStream.Position & 0xf) != 0)
w.Write((byte)0);
// Store section table offset back in the file header
long shoff = w.BaseStream.Position;
w.Seek((int)e_shoff_offset, System.IO.SeekOrigin.Begin);
w.Write((uint)shoff);
w.Seek((int)shoff, System.IO.SeekOrigin.Begin);
// Write out section table
foreach(var s in sects)
{
if(s == null)
{
for (int i = 0; i < 10; i++)
w.Write((uint)0);
}
else
{
w.Write((uint)s.ShStrNdx);
switch(s.SectionType)
{
case Section.SectType.NoBits:
w.Write((uint)8);
break;
case Section.SectType.Note:
w.Write((uint)7);
break;
case Section.SectType.ProgBits:
w.Write((uint)1);
break;
case Section.SectType.Rela:
w.Write((uint)4);
break;
case Section.SectType.StrTab:
w.Write((uint)3);
break;
case Section.SectType.SymTab:
w.Write((uint)2);
break;
case Section.SectType.Unknown:
w.Write((uint)0);
break;
}
uint sh_flags = 0;
if (s.Alloc)
sh_flags |= 0x2;
if (s.Write)
sh_flags |= 0x1;
if (s.Exec)
sh_flags |= 0x4;
w.Write(sh_flags);
w.Write((uint)0); // sh_addr
w.Write((uint)s.FileOffset);
w.Write((uint)s.SectionSize);
switch(s.SectionType)
{
case Section.SectType.Rela:
w.Write((uint)symtab.SectionIdx);
w.Write((uint)s.RelocSectionIdx);
break;
case Section.SectType.SymTab:
w.Write((uint)strtab.SectionIdx);
w.Write((uint)max_local);
break;
default:
w.Write((uint)0);
w.Write((uint)0);
break;
}
w.Write((uint)4); // sh_addralign
switch(s.SectionType)
{
case Section.SectType.Rela:
w.Write((uint)12);
break;
case Section.SectType.SymTab:
w.Write((uint)16);
break;
default:
w.Write((uint)0);
break;
}
}
}
}