private uint Relocate386Section(SectionInfo ps, int i)
{
// A section such as .rel.dyn or .rel.plt (without an addend field).
// Each entry has 2 words: r_offet and r_info. The r_offset is just the offset from the beginning
// of the section (section given by the section header's sh_info) to the word to be modified.
// r_info has the type in the bottom byte, and a symbol table index in the top 3 bytes.
// A symbol table offset of 0 (STN_UNDEF) means use value 0. The symbol table involved comes from
// the section header's sh_link field.
var pReloc = loader.CreateReader(ps.uHostAddr);
uint size = ps.uSectionSize;
// NOTE: the r_offset is different for .o files (E_REL in the e_type header field) than for exe's
// and shared objects!
ADDRESS destNatOrigin = 0, destHostOrigin = 0;
if (e_type == Elf32_Ehdr.E_REL)
{
int destSection = loader.m_sh_info[i];
destNatOrigin = loader.Sections[destSection].uNativeAddr;
destHostOrigin = loader.Sections[destSection].uHostAddr;
}
int symSection = loader.m_sh_link[i]; // Section index for the associated symbol table
int strSection = loader.m_sh_link[symSection]; // Section index for the string section assoc with this
uint pStrSection = loader.Sections[strSection].uHostAddr;
Elf32_Sym[] symOrigin = loader.LoadElf32Symbols(loader.Sections[symSection]); // Elf32_sym's
var rdr = loader.CreateReader(0);
var wrt = loader.CreateWriter();
for (uint u = 0; u < size; u += 2 * sizeof(uint))
{
uint r_offset = pReloc.ReadUInt32();
uint info = pReloc.ReadUInt32();
byte relType = (byte)info;
uint symTabIndex = info >> 8;
uint pRelWord; // Pointer to the word to be relocated
if (e_type == Elf32_Ehdr.E_REL)
{
pRelWord = (destHostOrigin + r_offset);
}
else
{
if (r_offset == 0)
{
continue;
}
SectionInfo destSec = loader.GetSectionInfoByAddr(r_offset);
pRelWord = (destSec.uHostAddr - destSec.uNativeAddr + r_offset);
destNatOrigin = 0;
}
ADDRESS A, S = 0, P;
int nsec;
switch (relType)
{
case 0: // R_386_NONE: just ignore (common)
break;
case 1: // R_386_32: S + A
S = symOrigin[symTabIndex].st_value;
if (e_type == Elf32_Ehdr.E_REL)
{
nsec = symOrigin[symTabIndex].st_shndx;
if (0 <= nsec && nsec < loader.Sections.Length)
{
S += loader.GetSectionInfo(nsec).uNativeAddr;
}
}
A = rdr.ReadUInt32(pRelWord);
wrt.WriteUInt32(pRelWord, S + A);
break;
case 2: // R_386_PC32: S + A - P
if (symOrigin[symTabIndex].ELF32_ST_TYPE == ElfImageLoader.STT_SECTION)
{
nsec = symOrigin[symTabIndex].st_shndx;
if (nsec >= 0 && nsec < loader.Sections.Length)
{
S = loader.GetSectionInfo(nsec).uNativeAddr;
}
}
else
{
S = symOrigin[symTabIndex].st_value;
if (S == 0)
{
// This means that the symbol doesn't exist in this module, and is not accessed
// through the PLT, i.e. it will be statically linked, e.g. strcmp. We have the
// name of the symbol right here in the symbol table entry, but the only way
// to communicate with the loader is through the target address of the call.
// So we use some very improbable addresses (e.g. -1, -2, etc) and give them entries
// in the symbol table
uint nameOffset = symOrigin[symTabIndex].st_name;
uint pName = pStrSection + nameOffset;
// this is too slow, I'm just going to assume it is 0
//S = GetAddressByName(pName);
//if (S == (e_type == E_REL ? 0x8000000 : 0)) {
S = nextFakeLibAddr--; // Allocate a new fake address
loader.AddSymbol(S, loader.ReadAsciizString(pName));
//}
}
else if (e_type == Elf32_Ehdr.E_REL)
{
nsec = symOrigin[symTabIndex].st_shndx;
if (nsec >= 0 && nsec < loader.Sections.Length)
{
S += loader.GetSectionInfo(nsec).uNativeAddr;
}
}
}
A = rdr.ReadUInt32(pRelWord);
P = destNatOrigin + r_offset;
wrt.WriteUInt32(pRelWord, S + A - P);
break;
case 7:
case 8: // R_386_RELATIVE
break; // No need to do anything with these, if a shared object
default:
throw new NotImplementedException("Relocation type " + (int)relType + " not handled yet");
}
}
return(nextFakeLibAddr);
}
