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| //===- OutputSections.cpp -------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "OutputSections.h"
#include "InputChunks.h"
#include "InputFiles.h"
#include "OutputSegment.h"
#include "WriterUtils.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Threads.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/LEB128.h"
#define DEBUG_TYPE "lld"
using namespace llvm;
using namespace llvm::wasm;
namespace lld {
// Returns a string, e.g. "FUNCTION(.text)".
std::string toString(const wasm::OutputSection &sec) {
if (!sec.name.empty())
return (sec.getSectionName() + "(" + sec.name + ")").str();
return sec.getSectionName();
}
namespace wasm {
static StringRef sectionTypeToString(uint32_t sectionType) {
switch (sectionType) {
case WASM_SEC_CUSTOM:
return "CUSTOM";
case WASM_SEC_TYPE:
return "TYPE";
case WASM_SEC_IMPORT:
return "IMPORT";
case WASM_SEC_FUNCTION:
return "FUNCTION";
case WASM_SEC_TABLE:
return "TABLE";
case WASM_SEC_MEMORY:
return "MEMORY";
case WASM_SEC_GLOBAL:
return "GLOBAL";
case WASM_SEC_EVENT:
return "EVENT";
case WASM_SEC_EXPORT:
return "EXPORT";
case WASM_SEC_START:
return "START";
case WASM_SEC_ELEM:
return "ELEM";
case WASM_SEC_CODE:
return "CODE";
case WASM_SEC_DATA:
return "DATA";
case WASM_SEC_DATACOUNT:
return "DATACOUNT";
default:
fatal("invalid section type");
}
}
StringRef OutputSection::getSectionName() const {
return sectionTypeToString(type);
}
void OutputSection::createHeader(size_t bodySize) {
raw_string_ostream os(header);
debugWrite(os.tell(), "section type [" + getSectionName() + "]");
encodeULEB128(type, os);
writeUleb128(os, bodySize, "section size");
os.flush();
log("createHeader: " + toString(*this) + " body=" + Twine(bodySize) +
" total=" + Twine(getSize()));
}
void CodeSection::finalizeContents() {
raw_string_ostream os(codeSectionHeader);
writeUleb128(os, functions.size(), "function count");
os.flush();
bodySize = codeSectionHeader.size();
for (InputFunction *func : functions) {
func->outputOffset = bodySize;
func->calculateSize();
bodySize += func->getSize();
}
createHeader(bodySize);
}
void CodeSection::writeTo(uint8_t *buf) {
log("writing " + toString(*this));
log(" size=" + Twine(getSize()));
log(" headersize=" + Twine(header.size()));
log(" codeheadersize=" + Twine(codeSectionHeader.size()));
buf += offset;
// Write section header
memcpy(buf, header.data(), header.size());
buf += header.size();
// Write code section headers
memcpy(buf, codeSectionHeader.data(), codeSectionHeader.size());
// Write code section bodies
for (const InputChunk *chunk : functions)
chunk->writeTo(buf);
}
uint32_t CodeSection::getNumRelocations() const {
uint32_t count = 0;
for (const InputChunk *func : functions)
count += func->getNumRelocations();
return count;
}
void CodeSection::writeRelocations(raw_ostream &os) const {
for (const InputChunk *c : functions)
c->writeRelocations(os);
}
void DataSection::finalizeContents() {
raw_string_ostream os(dataSectionHeader);
unsigned segmentCount =
std::count_if(segments.begin(), segments.end(),
[](OutputSegment *segment) { return !segment->isBss; });
writeUleb128(os, segmentCount, "data segment count");
os.flush();
bodySize = dataSectionHeader.size();
assert((!config->isPic || segments.size() <= 1) &&
"Currenly only a single data segment is supported in PIC mode");
for (OutputSegment *segment : segments) {
if (segment->isBss)
continue;
raw_string_ostream os(segment->header);
writeUleb128(os, segment->initFlags, "init flags");
if (segment->initFlags & WASM_SEGMENT_HAS_MEMINDEX)
writeUleb128(os, 0, "memory index");
if ((segment->initFlags & WASM_SEGMENT_IS_PASSIVE) == 0) {
WasmInitExpr initExpr;
if (config->isPic) {
initExpr.Opcode = WASM_OPCODE_GLOBAL_GET;
initExpr.Value.Global = WasmSym::memoryBase->getGlobalIndex();
} else {
initExpr.Opcode = WASM_OPCODE_I32_CONST;
initExpr.Value.Int32 = segment->startVA;
}
writeInitExpr(os, initExpr);
}
writeUleb128(os, segment->size, "segment size");
os.flush();
segment->sectionOffset = bodySize;
bodySize += segment->header.size() + segment->size;
log("Data segment: size=" + Twine(segment->size) + ", startVA=" +
Twine::utohexstr(segment->startVA) + ", name=" + segment->name);
for (InputSegment *inputSeg : segment->inputSegments)
inputSeg->outputOffset = segment->sectionOffset + segment->header.size() +
inputSeg->outputSegmentOffset;
}
createHeader(bodySize);
}
void DataSection::writeTo(uint8_t *buf) {
log("writing " + toString(*this) + " size=" + Twine(getSize()) +
" body=" + Twine(bodySize));
buf += offset;
// Write section header
memcpy(buf, header.data(), header.size());
buf += header.size();
// Write data section headers
memcpy(buf, dataSectionHeader.data(), dataSectionHeader.size());
for (const OutputSegment *segment : segments) {
if (segment->isBss)
continue;
// Write data segment header
uint8_t *segStart = buf + segment->sectionOffset;
memcpy(segStart, segment->header.data(), segment->header.size());
// Write segment data payload
for (const InputChunk *chunk : segment->inputSegments)
chunk->writeTo(buf);
}
}
uint32_t DataSection::getNumRelocations() const {
uint32_t count = 0;
for (const OutputSegment *seg : segments)
for (const InputChunk *inputSeg : seg->inputSegments)
count += inputSeg->getNumRelocations();
return count;
}
void DataSection::writeRelocations(raw_ostream &os) const {
for (const OutputSegment *seg : segments)
for (const InputChunk *c : seg->inputSegments)
c->writeRelocations(os);
}
bool DataSection::isNeeded() const {
for (const OutputSegment *seg : segments)
if (!seg->isBss)
return true;
return false;
}
void CustomSection::finalizeContents() {
raw_string_ostream os(nameData);
encodeULEB128(name.size(), os);
os << name;
os.flush();
for (InputSection *section : inputSections) {
section->outputOffset = payloadSize;
section->outputSec = this;
payloadSize += section->getSize();
}
createHeader(payloadSize + nameData.size());
}
void CustomSection::writeTo(uint8_t *buf) {
log("writing " + toString(*this) + " size=" + Twine(getSize()) +
" chunks=" + Twine(inputSections.size()));
assert(offset);
buf += offset;
// Write section header
memcpy(buf, header.data(), header.size());
buf += header.size();
memcpy(buf, nameData.data(), nameData.size());
buf += nameData.size();
// Write custom sections payload
for (const InputSection *section : inputSections)
section->writeTo(buf);
}
uint32_t CustomSection::getNumRelocations() const {
uint32_t count = 0;
for (const InputSection *inputSect : inputSections)
count += inputSect->getNumRelocations();
return count;
}
void CustomSection::writeRelocations(raw_ostream &os) const {
for (const InputSection *s : inputSections)
s->writeRelocations(os);
}
} // namespace wasm
} // namespace lld
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