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support for absolute references to local symbols
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@StanHash
StanHash committed Dec 10, 2017
1 parent 204cf66 commit 67cd9d3
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Showing 8 changed files with 187 additions and 133 deletions.
3 changes: 3 additions & 0 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,9 @@ set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -static")
set(SOURCE_LIST
main.cpp

core/util.h
core/util.cpp

core/binary_file.h
core/binary_file.cpp

Expand Down
161 changes: 103 additions & 58 deletions core/event_object.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,13 +4,26 @@
#include <algorithm>

#include "../ea/event_section.h"
#include "util.h"

namespace lyn {

void event_object::append_from_elf(const elf_file& elfFile) {
std::vector<section_data> newSections(elfFile.sections().size());
std::vector<bool> outMap(elfFile.sections().size(), false);

auto getLocalSymbolName = [this] (int section, int index) -> std::string {
std::string result;
result.reserve(2 + 8 + 4 + 4);

result.append("_L");
result.append(stan::to_hex_digits(size(), 8));
result.append(stan::to_hex_digits(section, 4));
result.append(stan::to_hex_digits(index, 4));

return result;
};

// Initializing written Sections from relevant elf sections

for (int i=0; i<newSections.size(); ++i) {
Expand All @@ -29,9 +42,11 @@ void event_object::append_from_elf(const elf_file& elfFile) {

// Initializing labels, mappings & relocations from other elf sections

for (auto& elfSection : elfFile.sections()) {
for (int sectionIndex=0; sectionIndex<elfFile.sections().size(); ++sectionIndex) {
auto& elfSection = elfFile.sections()[sectionIndex];

if (elfSection.sh_type == elf::SHT_SYMTAB) {
int symbolCount = elfSection.sh_size / 0x10;
int symbolCount = elfSection.sh_size / elfSection.sh_entsize;

auto& nameElfSection = elfFile.sections()[elfSection.sh_link];

Expand All @@ -51,36 +66,28 @@ void event_object::append_from_elf(const elf_file& elfFile) {

std::string symbolName = elfFile.string(nameElfSection, sym.st_name);

switch (sym.type()) {
case elf::STT_FUNC:
// sym.st_value &= ~1; // remove eventual thumb bit
case elf::STT_OBJECT: {
if (sym.bind() == elf::STB_GLOBAL)
sectionData.symbols().push_back({ symbolName, sym.st_value, false });

break;
}

case elf::STT_NOTYPE: {
if (sym.bind() != elf::STB_LOCAL)
break;

if (sym.type() == elf::STT_NOTYPE && sym.bind() == elf::STB_LOCAL) {
std::string subString = symbolName.substr(0, 3);

if ((symbolName == "$t") || (subString == "$t."))
if ((symbolName == "$t") || (subString == "$t.")) {
sectionData.set_mapping(sym.st_value, mapping::Thumb);
else if ((symbolName == "$a") || (subString == "$a."))
continue;
} else if ((symbolName == "$a") || (subString == "$a.")) {
sectionData.set_mapping(sym.st_value, mapping::ARM);
else if ((symbolName == "$d") || (subString == "$d."))
continue;
} else if ((symbolName == "$d") || (subString == "$d.")) {
sectionData.set_mapping(sym.st_value, mapping::Data);

break;
continue;
}
}

}
if (sym.bind() == elf::STB_LOCAL)
symbolName = getLocalSymbolName(sectionIndex, i);

sectionData.symbols().push_back({ symbolName, sym.st_value, (sym.bind() == elf::STB_LOCAL) });
}
} else if (elfSection.sh_type == elf::SHT_REL) {
int relCount = elfSection.sh_size / 0x08;
int relCount = elfSection.sh_size / elfSection.sh_entsize;

auto& symbolSection = elfFile.sections()[elfSection.sh_link];
auto& symbolNameSection = elfFile.sections()[symbolSection.sh_link];
Expand All @@ -89,12 +96,16 @@ void event_object::append_from_elf(const elf_file& elfFile) {

for (int i=0; i<relCount; ++i) {
auto rel = elfFile.rel(elfSection, i);
auto name = elfFile.string(symbolNameSection, elfFile.symbol(symbolSection, rel.symId()).st_name);
auto sym = elfFile.symbol(symbolSection, rel.symId());
std::string name = elfFile.string(symbolNameSection, sym.st_name);

if (sym.bind() == elf::STB_LOCAL)
name = getLocalSymbolName(elfSection.sh_link, rel.symId());

sectionData.relocations().push_back({ std::string(name), 0, rel.type(), rel.r_offset });
}
} else if (elfSection.sh_type == elf::SHT_RELA) {
int relCount = elfSection.sh_size / 0x0C;
int relCount = elfSection.sh_size / elfSection.sh_entsize;

auto& symbolSection = elfFile.sections()[elfSection.sh_link];
auto& symbolNameSection = elfFile.sections()[symbolSection.sh_link];
Expand All @@ -103,7 +114,11 @@ void event_object::append_from_elf(const elf_file& elfFile) {

for (int i=0; i<relCount; ++i) {
auto rela = elfFile.rela(elfSection, i);
auto name = elfFile.string(symbolNameSection, elfFile.symbol(symbolSection, rela.symId()).st_name);
auto sym = elfFile.symbol(symbolSection, rela.symId());
std::string name = elfFile.string(symbolNameSection, sym.st_name);

if (sym.bind() == elf::STB_LOCAL)
name = getLocalSymbolName(elfSection.sh_link, rela.symId());

sectionData.relocations().push_back({ std::string(name), rela.r_addend, rela.type(), rela.r_offset });
}
Expand All @@ -124,13 +139,18 @@ void event_object::append_from_elf(const elf_file& elfFile) {
}
}

void event_object::make_trampolines() {
void event_object::try_transform_relatives() {
section_data trampolineData;

for (auto& relocation : relocations()) {
if (auto relocatelet = mRelocator.get_relocatelet(relocation.type)) {
if (!relocatelet->is_absolute() && relocatelet->can_make_trampoline()) {
std::string renamed = std::string("LYN_PROXY_").append(relocation.symbolName);
std::string renamed;
renamed.reserve(4 + relocation.symbolName.size());

renamed.append("_LP_"); // local proxy
renamed.append(relocation.symbolName);

bool exists = false;

for (auto& sym : symbols())
Expand All @@ -153,16 +173,13 @@ void event_object::make_trampolines() {
combine_with(std::move(trampolineData));
}

void event_object::link_temporaries() {
void event_object::try_relocate_relatives() {
relocations().erase(
std::remove_if(
relocations().begin(),
relocations().end(),
[this] (const section_data::relocation& relocation) -> bool {
for (auto& symbol : symbols()) {
if (!symbol.isLocal)
continue;

if (symbol.name != relocation.symbolName)
continue;

Expand All @@ -183,18 +200,18 @@ void event_object::link_temporaries() {
);
}

void event_object::link_locals() {
void event_object::try_relocate_absolutes() {
relocations().erase(
std::remove_if(
relocations().begin(),
relocations().end(),
[this] (const section_data::relocation& relocation) -> bool {
for (auto& symbol : symbols()) {
for (auto& symbol : mAbsoluteSymbols) {
if (symbol.name != relocation.symbolName)
continue;

if (auto relocatelet = mRelocator.get_relocatelet(relocation.type)) {
if (!relocatelet->is_absolute()) {
if (relocatelet->is_absolute()) {
relocatelet->apply_relocation(*this, relocation.offset, symbol.offset, relocation.addend);
return true;
}
Expand All @@ -210,30 +227,33 @@ void event_object::link_locals() {
);
}

void event_object::link_absolutes() {
relocations().erase(
void event_object::remove_unnecessary_symbols() {
symbols().erase(
std::remove_if(
relocations().begin(),
relocations().end(),
[this] (const section_data::relocation& relocation) -> bool {
for (auto& symbol : mAbsoluteSymbols) {
if (symbol.name != relocation.symbolName)
continue;

if (auto relocatelet = mRelocator.get_relocatelet(relocation.type)) {
if (relocatelet->is_absolute()) {
relocatelet->apply_relocation(*this, relocation.offset, symbol.offset, relocation.addend);
return true;
}
}
symbols().begin(),
symbols().end(),
[this] (const section_data::symbol& symbol) -> bool {
if (!symbol.isLocal)
return false; // symbol may be used outside of the scope of this object

return false;
}
for (auto& reloc : relocations())
if (reloc.symbolName == symbol.name)
return false; // a relocation is dependant on this symbol

return false;
return true; // symbol is local and unused, we can remove it safely (hopefully)
}
),
relocations().end()
symbols().end()
);
}

void event_object::cleanup() {
std::sort(
symbols().begin(),
symbols().end(),
[] (const section_data::symbol& a, const section_data::symbol& b) -> bool {
return a.offset < b.offset;
}
);
}

Expand Down Expand Up @@ -262,26 +282,51 @@ void event_object::write_events(std::ostream& output) const {
if (auto relocatelet = mRelocator.get_relocatelet(relocation.type))
events.set_code(relocation.offset, relocatelet->make_event_code(relocation.symbolName, relocation.addend));
else
throw std::runtime_error(std::string("RELOC ERROR: Unhandled relocation type ").append(std::to_string(relocation.type)));
throw std::runtime_error(std::string("unhandled relocation type #").append(std::to_string(relocation.type)));
}

events.compress_codes();
events.optimize();

if (!symbols().empty()) {
if (std::any_of(symbols().begin(), symbols().end(), [] (const section_data::symbol& sym) { return !sym.isLocal; })) {
output << "PUSH" << std::endl;
int currentOffset = 0;

for (auto& symbol : symbols()) {
if (symbol.isLocal)
continue;

output << "ORG (CURRENTOFFSET+$" << std::hex << (symbol.offset - currentOffset) << "); "
<< symbol.name << ":" << std::endl;
currentOffset = symbol.offset;
}

output << "POP" << std::endl << std::endl;
output << "POP" << std::endl;
}

events.write_to_stream(output);
if (std::any_of(symbols().begin(), symbols().end(), [] (const section_data::symbol& sym) { return sym.isLocal; })) {
output << "{" << std::endl;
output << "PUSH" << std::endl;

int currentOffset = 0;

for (auto& symbol : symbols()) {
if (!symbol.isLocal)
continue;

output << "ORG (CURRENTOFFSET+$" << std::hex << (symbol.offset - currentOffset) << "); "
<< symbol.name << ":" << std::endl;
currentOffset = symbol.offset;
}

output << "POP" << std::endl;

events.write_to_stream(output);

output << "}" << std::endl;
} else {
events.write_to_stream(output);
}
}

} // namespace lyn
11 changes: 7 additions & 4 deletions core/event_object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -18,11 +18,14 @@ class event_object : public section_data {
public:
void append_from_elf(const lyn::elf_file& elfFile);

void make_trampolines();
void try_transform_relatives();

void link_locals();
void link_temporaries();
void link_absolutes();
void try_relocate_relatives();
void try_relocate_absolutes();

void remove_unnecessary_symbols();

void cleanup();

std::vector<hook> get_hooks() const;

Expand Down
38 changes: 4 additions & 34 deletions core/section_data.cpp
View file
Original file line number Diff line number Diff line change
@@ -1,29 +1,12 @@
#include "section_data.h"

#include "../ea/event_section.h"
#include "util.h"

#include <algorithm>

namespace lyn {

std::string::value_type toHexDigit(std::uint32_t value) {
value = (value & 0xF);

if (value < 10)
return '0' + value;
return 'A' + (value - 10);
}

std::string toHexDigits(std::uint32_t value, int digits) {
std::string result;
result.resize(digits);

for (int i=0; i<digits; ++i)
result[digits-i-1] = toHexDigit(value >> (4*i));

return result;
}

event_section section_data::make_events() const {
event_section result;
result.resize(size());
Expand All @@ -41,23 +24,23 @@ event_section section_data::make_events() const {
case mapping::Data:
result.set_code(pos, lyn::event_code(
lyn::event_code::CODE_BYTE,
std::string("$").append(toHexDigits(byte_at(pos), 2))
std::string("$").append(stan::to_hex_digits(byte_at(pos), 2))
));
pos++;
break;

case mapping::Thumb:
result.set_code(pos, lyn::event_code(
lyn::event_code::CODE_SHORT,
std::string("$").append(toHexDigits(at<std::uint16_t>(pos), 4))
std::string("$").append(stan::to_hex_digits(at<std::uint16_t>(pos), 4))
));
pos += 2;
break;

case mapping::ARM:
result.set_code(pos, lyn::event_code(
lyn::event_code::CODE_WORD,
std::string("$").append(toHexDigits(at<std::uint32_t>(pos), 8))
std::string("$").append(stan::to_hex_digits(at<std::uint32_t>(pos), 8))
));
pos += 4;
break;
Expand Down Expand Up @@ -134,17 +117,4 @@ void section_data::combine_with(section_data&& other) {
binary_file::combine_with(other);
}

void section_data::remove_temp_symbols() {
symbols().erase(
std::remove_if(
symbols().begin(),
symbols().end(),
[] (const section_data::symbol& symbol) -> bool {
return symbol.isLocal;
}
),
symbols().end()
);
}

} // namespace lyn
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