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fe39edb1cf
mold/input_sections.cc
Rui Ueyama fe39edb1cf temporary
2021-01-09 22:30:56 +09:00

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#include "mold.h"
InputChunk::InputChunk(ObjectFile *file, const ElfShdr &shdr,
std::string_view name)
: file(file), shdr(shdr), name(name),
output_section(OutputSection::get_instance(name, shdr.sh_type, shdr.sh_flags)) {}
static std::string rel_to_string(u32 r_type) {
switch (r_type) {
case R_X86_64_NONE: return "R_X86_64_NONE";
case R_X86_64_8: return "R_X86_64_8";
case R_X86_64_16: return "R_X86_64_16";
case R_X86_64_32: return "R_X86_64_32";
case R_X86_64_32S: return "R_X86_64_32S";
case R_X86_64_64: return "R_X86_64_64";
case R_X86_64_PC8: return "R_X86_64_PC8";
case R_X86_64_PC16: return "R_X86_64_PC16";
case R_X86_64_PC32: return "R_X86_64_PC32";
case R_X86_64_PC64: return "R_X86_64_PC64";
case R_X86_64_GOT32: return "R_X86_64_GOT32";
case R_X86_64_GOTPC32: return "R_X86_64_GOTPC32";
case R_X86_64_GOTPCREL: return "R_X86_64_GOTPCREL";
case R_X86_64_GOTPCRELX: return "R_X86_64_GOTPCRELX";
case R_X86_64_REX_GOTPCRELX: return "R_X86_64_REX_GOTPCRELX";
case R_X86_64_PLT32: return "R_X86_64_PLT32";
case R_X86_64_TLSGD: return "R_X86_64_TLSGD";
case R_X86_64_TLSLD: return "R_X86_64_TLSLD";
case R_X86_64_TPOFF32: return "R_X86_64_TPOFF32";
case R_X86_64_DTPOFF32: return "R_X86_64_DTPOFF32";
case R_X86_64_TPOFF64: return "R_X86_64_TPOFF64";
case R_X86_64_DTPOFF64: return "R_X86_64_DTPOFF64";
case R_X86_64_GOTTPOFF: return "R_X86_64_GOTTPOFF";
}
unreachable();
}
static void overflow_check(u32 r_type, u64 val) {
switch (r_type) {
case R_X86_64_8:
if (val != (u8)val)
Error() << "relocation R_X86_64_8 out of range: " << val
<< " is not in [0, 255]";
return;
case R_X86_64_PC8:
if (val != (i8)val)
Error() << "relocation R_X86_64_PC8 out of range: " << (i64)val
<< " is not in [-128, 127]";
return;
case R_X86_64_16:
if (val != (u16)val)
Error() << "relocation R_X86_64_16 out of range: " << val
<< " is not in [0, 65535]";
return;
case R_X86_64_PC16:
if (val != (i16)val)
Error() << "relocation R_X86_64_PC16 out of range: " << (i64)val
<< " is not in [-32768, 32767]";
return;
case R_X86_64_32:
if (val != (u32)val)
Error() << "relocation R_X86_64_32 out of range: " << val
<< " is not in [0, 4294967296]";
return;
case R_X86_64_32S:
case R_X86_64_PC32:
case R_X86_64_GOT32:
case R_X86_64_GOTPC32:
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_REX_GOTPCRELX:
case R_X86_64_PLT32:
case R_X86_64_TLSGD:
case R_X86_64_TLSLD:
case R_X86_64_TPOFF32:
case R_X86_64_DTPOFF32:
case R_X86_64_GOTTPOFF:
if (val != (i32)val)
Error() << "relocation " << rel_to_string(r_type) << " out of range: "
<< (i64)val << " is not in [-2147483648, 2147483647]";
return;
case R_X86_64_NONE:
case R_X86_64_64:
case R_X86_64_PC64:
case R_X86_64_TPOFF64:
case R_X86_64_DTPOFF64:
return;
}
unreachable();
}
static int get_rel_size(u32 r_type) {
switch (r_type) {
case R_X86_64_NONE:
return 0;
case R_X86_64_8:
case R_X86_64_PC8:
return 1;
case R_X86_64_16:
case R_X86_64_PC16:
return 2;
case R_X86_64_32:
case R_X86_64_32S:
case R_X86_64_PC32:
case R_X86_64_GOT32:
case R_X86_64_GOTPC32:
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_REX_GOTPCRELX:
case R_X86_64_PLT32:
case R_X86_64_TLSGD:
case R_X86_64_TLSLD:
case R_X86_64_TPOFF32:
case R_X86_64_DTPOFF32:
case R_X86_64_GOTTPOFF:
return 4;
case R_X86_64_64:
case R_X86_64_PC64:
case R_X86_64_TPOFF64:
case R_X86_64_DTPOFF64:
return 8;
}
unreachable();
}
void InputSection::copy_buf() {
if (shdr.sh_type == SHT_NOBITS || shdr.sh_size == 0)
return;
// Copy data
std::string_view view = file->get_string(shdr);
memcpy(out::buf + output_section->shdr.sh_offset + offset,
view.data(), view.size());
// Apply relocations
u8 *base = out::buf + output_section->shdr.sh_offset + offset;
int ref_idx = 0;
ElfRela *dynrel = nullptr;
if (out::reldyn)
dynrel = (ElfRela *)(out::buf + out::reldyn->shdr.sh_offset +
file->reldyn_offset + reldyn_offset);
for (int i = 0; i < rels.size(); i++) {
const ElfRela &rel = rels[i];
Symbol &sym = *file->symbols[rel.r_sym];
u8 *loc = base + rel.r_offset;
const StringPieceRef *ref = nullptr;
if (has_rel_piece[i])
ref = &rel_pieces[ref_idx++];
auto write = [&](u64 val) {
overflow_check(rel.r_type, val);
switch (get_rel_size(rel.r_type)) {
case 1: *loc = val; return;
case 2: *(u16 *)loc = val; return;
case 4: *(u32 *)loc = val; return;
case 8: *(u64 *)loc = val; return;
}
unreachable();
};
#define S (ref ? ref->piece->get_addr() : sym.get_addr())
#define A (ref ? ref->addend : rel.r_addend)
#define P (output_section->shdr.sh_addr + offset + rel.r_offset)
#define L sym.get_plt_addr()
#define G (sym.get_got_addr() - out::got->shdr.sh_addr)
#define GOT out::got->shdr.sh_addr
switch (rel_types[i]) {
case R_NONE:
break;
case R_ABS:
write(S + A);
if (sym.needs_relative_rel()) {
assert(get_rel_size(rel.r_type) == 8);
memset(dynrel, 0, sizeof(*dynrel));
dynrel->r_offset = P;
dynrel->r_type = R_X86_64_RELATIVE;
dynrel->r_addend = S + A;
dynrel++;
}
break;
case R_DYN:
memset(dynrel, 0, sizeof(*dynrel));
dynrel->r_offset = P;
dynrel->r_type = R_X86_64_64;
dynrel->r_sym = sym.dynsym_idx;
dynrel->r_addend = A;
dynrel++;
break;
case R_PC:
write(S + A - P);
break;
case R_GOT:
write(G + A);
break;
case R_GOTPC:
write(GOT + A - P);
break;
case R_GOTPCREL:
write(G + GOT + A - P);
break;
case R_PLT:
write(L + A - P);
break;
case R_TLSGD:
write(sym.get_tlsgd_addr() + A - P);
break;
case R_TLSGD_RELAX_LE: {
// Relax GD to LE
static const u8 insn[] = {
0x64, 0x48, 0x8b, 0x04, 0x25, 0, 0, 0, 0, // mov %fs:0, %rax
0x48, 0x8d, 0x80, 0, 0, 0, 0, // lea x@tpoff, %rax
};
memcpy(loc - 4, insn, sizeof(insn));
*(u32 *)(loc + 8) = S - out::tls_end + A + 4;
i++;
break;
}
case R_TLSLD:
write(sym.get_tlsld_addr() + A - P);
break;
case R_TLSLD_RELAX_LE: {
// Relax LD to LE
static const u8 insn[] = {
// mov %fs:0, %rax
0x66, 0x66, 0x66, 0x64, 0x48, 0x8b, 0x04, 0x25, 0, 0, 0, 0,
};
memcpy(loc - 3, insn, sizeof(insn));
i++;
break;
}
case R_TPOFF:
write(S + A - out::tls_end);
break;
case R_GOTTPOFF:
write(sym.get_gottpoff_addr() + A - P);
break;
default:
unreachable();
}
#undef S
#undef A
#undef P
#undef L
#undef G
#undef GOT
}
}
void InputSection::scan_relocations() {
if (!(shdr.sh_flags & SHF_ALLOC))
return;
reldyn_offset = file->num_dynrel * sizeof(ElfRela);
static Counter counter("relocs");
counter.inc(rels.size());
for (int i = 0; i < rels.size(); i++) {
const ElfRela &rel = rels[i];
Symbol &sym = *file->symbols[rel.r_sym];
if (!sym.file || sym.is_placeholder) {
file->has_error = true;
continue;
}
switch (rel.r_type) {
case R_X86_64_NONE:
rel_types[i] = R_NONE;
break;
case R_X86_64_8:
case R_X86_64_16:
case R_X86_64_32:
case R_X86_64_32S:
if (config.pie)
Error() << *this << ": " << rel_to_string(rel.r_type)
<< " relocation against symbol `" << sym.name
<< "' can not be used when making a PIE object;"
<< " recompile with -fPIE";
if (!sym.is_imported) {
rel_types[i] = R_ABS;
} else if (sym.type == STT_OBJECT) {
rel_types[i] = R_ABS;
sym.flags |= NEEDS_COPYREL;
} else {
rel_types[i] = R_PLT;
sym.flags |= NEEDS_PLT;
}
break;
case R_X86_64_64:
if (sym.is_imported) {
rel_types[i] = R_DYN;
sym.flags |= NEEDS_DYNSYM;
file->num_dynrel++;
} else {
rel_types[i] = R_ABS;
if (sym.needs_relative_rel())
file->num_dynrel++;
}
break;
case R_X86_64_PC8:
case R_X86_64_PC16:
case R_X86_64_PC32:
case R_X86_64_PC64:
if (!sym.is_imported) {
rel_types[i] = R_PC;
} else if (sym.type == STT_OBJECT) {
rel_types[i] = R_PC;
sym.flags |= NEEDS_COPYREL;
} else {
rel_types[i] = R_PLT;
sym.flags |= NEEDS_PLT;
}
break;
case R_X86_64_GOT32:
rel_types[i] = R_GOT;
sym.flags |= NEEDS_GOT;
break;
case R_X86_64_GOTPC32:
rel_types[i] = R_GOTPC;
sym.flags |= NEEDS_GOT;
break;
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_REX_GOTPCRELX:
rel_types[i] = R_GOTPCREL;
sym.flags |= NEEDS_GOT;
break;
case R_X86_64_PLT32:
if (sym.is_imported || sym.type == STT_GNU_IFUNC) {
rel_types[i] = R_PLT;
sym.flags |= NEEDS_PLT;
} else {
rel_types[i] = R_PC;
}
break;
case R_X86_64_TLSGD:
if (rels[i + 1].r_type != R_X86_64_PLT32)
Error() << *this << ": TLSGD reloc not followed by PLT32";
if (sym.is_imported) {
rel_types[i] = R_TLSGD;
sym.flags |= NEEDS_TLSGD;
} else {
rel_types[i] = R_TLSGD_RELAX_LE;
i++;
}
break;
case R_X86_64_TLSLD:
if (rels[i + 1].r_type != R_X86_64_PLT32)
Error() << *this << ": TLSLD reloc not followed by PLT32";
if (sym.is_imported) {
rel_types[i] = R_TLSLD;
sym.flags |= NEEDS_TLSLD;
} else {
rel_types[i] = R_TLSLD_RELAX_LE;
i++;
}
break;
case R_X86_64_TPOFF32:
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF64:
case R_X86_64_DTPOFF64:
rel_types[i] = R_TPOFF;
break;
case R_X86_64_GOTTPOFF:
rel_types[i] = R_GOTTPOFF;
sym.flags |= NEEDS_GOTTPOFF;
break;
default:
Error() << *this << ": unknown relocation: " << rel.r_type;
}
}
}
void InputSection::report_undefined_symbols() {
if (!(shdr.sh_flags & SHF_ALLOC))
return;
for (const ElfRela &rel : rels) {
Symbol &sym = *file->symbols[rel.r_sym];
if (!sym.file || sym.is_placeholder)
std::cerr << "undefined symbol: " << *file << ": " << sym.name << "\n";
}
}
MergeableSection::MergeableSection(InputSection *isec, std::string_view data)
: InputChunk(isec->file, isec->shdr, isec->name),
parent(*MergedSection::get_instance(isec->name, isec->shdr.sh_type,
isec->shdr.sh_flags)) {
u32 offset = 0;
while (!data.empty()) {
size_t end = data.find('\0');
if (end == std::string_view::npos)
Error() << *this << ": string is not null terminated";
std::string_view substr = data.substr(0, end + 1);
data = data.substr(end + 1);
StringPiece *piece = parent.map.insert(substr, StringPiece(substr));
pieces.push_back(piece);
piece_offsets.push_back(offset);
offset += substr.size();
}
static Counter counter("string_pieces");
counter.inc(pieces.size());
}
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