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647f2c485b
mold/input_sections.cc
Rui Ueyama 647f2c485b temporary
2021-01-17 17:24:35 +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(InputSection *sec, Symbol &sym, u32 r_type, u64 val) {
auto out_of_range = [&](std::string range) {
Error() << *sec << ": relocation " << rel_to_string(r_type)
<< " against " << sym.name << " out of range: "
<< val << " is not in [" << range << "]";
};
switch (r_type) {
case R_X86_64_8:
if (val != (u8)val)
out_of_range("0, 255");
return;
case R_X86_64_PC8:
if (val != (i8)val)
out_of_range("-128, 127");
return;
case R_X86_64_16:
if (val != (u16)val)
out_of_range("0, 65535");
return;
case R_X86_64_PC16:
if (val != (i16)val)
out_of_range("-32768, 32767");
return;
case R_X86_64_32:
if (val != (u32)val)
out_of_range("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)
out_of_range("-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 void write_val(u32 r_type, u8 *loc, u64 val) {
switch (r_type) {
case R_X86_64_NONE:
return;
case R_X86_64_8:
case R_X86_64_PC8:
*loc = val;
return;
case R_X86_64_16:
case R_X86_64_PC16:
*(u16 *)loc = val;
return;
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:
*(u32 *)loc = val;
return;
case R_X86_64_64:
case R_X86_64_PC64:
case R_X86_64_TPOFF64:
case R_X86_64_DTPOFF64:
*(u64 *)loc = val;
return;
}
unreachable();
}
void InputSection::copy_buf() {
if (shdr.sh_type == SHT_NOBITS || shdr.sh_size == 0)
return;
// Copy data
u8 *base = out::buf + output_section->shdr.sh_offset + offset;
copy_contents(base);
// Apply relocations
if (shdr.sh_flags & SHF_ALLOC)
apply_reloc_alloc(base);
else
apply_reloc_nonalloc(base);
}
void InputSection::copy_contents(u8 *base) {
std::string_view contents = file->get_string(shdr);
memcpy(base, contents.data(), contents.size());
}
void InputSection::apply_reloc_alloc(u8 *base) {
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(this, sym, rel.r_type, val);
write_val(rel.r_type, loc, val);
};
#define S (ref ? ref->piece->get_addr() \
: (sym.plt_idx == -1 ? sym.get_addr() : sym.get_plt_addr()))
#define A (ref ? ref->addend : rel.r_addend)
#define P (output_section->shdr.sh_addr + offset + rel.r_offset)
#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);
break;
case R_ABS_DYN:
write(S + A);
*dynrel++ = {P, R_X86_64_RELATIVE, 0, (i64)(S + A)};
break;
case R_DYN:
*dynrel++ = {P, R_X86_64_64, sym.dynsym_idx, A};
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_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(out::got->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_DTPOFF:
write(S + A - out::tls_begin);
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 G
#undef GOT
}
}
void InputSection::apply_reloc_nonalloc(u8 *base) {
static Counter counter("reloc_nonalloc");
counter.inc(rels.size());
int ref_idx = 0;
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) {
Error() << "undefined symbol: " << *file << ": " << sym.name;
continue;
}
const StringPieceRef *ref = nullptr;
if (has_rel_piece[i])
ref = &rel_pieces[ref_idx++];
switch (rel.r_type) {
case R_X86_64_NONE:
break;
case R_X86_64_8:
case R_X86_64_16:
case R_X86_64_32:
case R_X86_64_32S:
case R_X86_64_64: {
u8 *loc = base + rel.r_offset;
u64 val = ref ? ref->piece->get_addr() : sym.get_addr();
overflow_check(this, sym, rel.r_type, val);
write_val(rel.r_type, loc, val);
break;
}
case R_X86_64_PC8:
case R_X86_64_PC16:
case R_X86_64_PC32:
case R_X86_64_PC64:
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_DTPOFF32:
case R_X86_64_DTPOFF64:
case R_X86_64_TPOFF32:
case R_X86_64_TPOFF64:
case R_X86_64_GOTTPOFF:
Error() << *this << ": invalid relocation for non-allocated sections: "
<< rel.r_type;
break;
default:
Error() << *this << ": unknown relocation: " << rel.r_type;
}
}
}
void InputSection::scan_relocations() {
if (!(shdr.sh_flags & SHF_ALLOC))
return;
static Counter counter("reloc_alloc");
counter.inc(rels.size());
this->reldyn_offset = file->num_dynrel * sizeof(ElfRela);
this->rel_types.resize(rels.size());
for (int i = 0; i < rels.size(); i++) {
const ElfRela &rel = rels[i];
Symbol &sym = *file->symbols[rel.r_sym];
bool is_readonly = !(shdr.sh_flags & SHF_WRITE);
bool is_code = (sym.st_type == STT_FUNC);
if (!sym.file || sym.is_placeholder) {
Error() << "undefined symbol: " << *file << ": " << sym.name;
continue;
}
auto report_error = [&]() {
Error() << *this << ": " << rel_to_string(rel.r_type)
<< " relocation against symbol `" << sym.name
<< "' can not be used; recompile with -fPIE";
};
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 && sym.is_relative())
report_error();
if (sym.is_imported)
sym.flags |= is_code ? NEEDS_PLT : NEEDS_COPYREL;
rel_types[i] = R_ABS;
break;
case R_X86_64_64:
if (config.pie) {
if (sym.is_imported) {
if (is_readonly)
report_error();
sym.flags |= NEEDS_DYNSYM;
rel_types[i] = R_DYN;
file->num_dynrel++;
} else if (sym.is_relative()) {
if (is_readonly)
report_error();
rel_types[i] = R_ABS_DYN;
file->num_dynrel++;
} else {
rel_types[i] = R_ABS;
}
} else {
if (sym.is_imported)
sym.flags |= is_code ? NEEDS_PLT : NEEDS_COPYREL;
rel_types[i] = R_ABS;
}
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)
sym.flags |= is_code ? NEEDS_PLT : NEEDS_COPYREL;
rel_types[i] = R_PC;
break;
case R_X86_64_GOT32:
sym.flags |= NEEDS_GOT;
rel_types[i] = R_GOT;
break;
case R_X86_64_GOTPC32:
sym.flags |= NEEDS_GOT;
rel_types[i] = R_GOTPC;
break;
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_REX_GOTPCRELX:
sym.flags |= NEEDS_GOT;
rel_types[i] = R_GOTPCREL;
break;
case R_X86_64_PLT32:
if (sym.is_imported || sym.st_type == STT_GNU_IFUNC)
sym.flags |= NEEDS_PLT;
rel_types[i] = R_PC;
break;
case R_X86_64_TLSGD:
if (i + 1 == rels.size() || rels[i + 1].r_type != R_X86_64_PLT32)
Error() << *this << ": TLSGD reloc not followed by PLT32";
if (config.relax && !sym.is_imported) {
rel_types[i] = R_TLSGD_RELAX_LE;
i++;
} else {
sym.flags |= NEEDS_TLSGD;
sym.flags |= NEEDS_DYNSYM;
rel_types[i] = R_TLSGD;
}
break;
case R_X86_64_TLSLD:
if (i + 1 == rels.size() || rels[i + 1].r_type != R_X86_64_PLT32)
Error() << *this << ": TLSLD reloc not followed by PLT32";
if (sym.is_imported)
Error() << *this << ": TLSLD reloc refers external symbol " << sym.name;
if (config.relax) {
rel_types[i] = R_TLSLD_RELAX_LE;
i++;
} else {
sym.flags |= NEEDS_TLSLD;
rel_types[i] = R_TLSLD;
}
break;
case R_X86_64_DTPOFF32:
case R_X86_64_DTPOFF64:
if (sym.is_imported)
Error() << *this << ": DTPOFF reloc refers external symbol " << sym.name;
rel_types[i] = config.relax ? R_TPOFF : R_DTPOFF;
break;
case R_X86_64_TPOFF32:
case R_X86_64_TPOFF64:
rel_types[i] = R_TPOFF;
break;
case R_X86_64_GOTTPOFF:
sym.flags |= NEEDS_GOTTPOFF;
rel_types[i] = R_GOTTPOFF;
break;
default:
Error() << *this << ": unknown relocation: " << rel.r_type;
}
}
}
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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