297 lines
9.0 KiB
C++
297 lines
9.0 KiB
C++
|
//===- ExportTrie.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
|
||
|
|
//
|
||
|
|
//===----------------------------------------------------------------------===//
|
||
|
|
//
|
||
|
|
// This is a partial implementation of the Mach-O export trie format. It's
|
||
|
|
// essentially a symbol table encoded as a compressed prefix trie, meaning that
|
||
|
|
// the common prefixes of each symbol name are shared for a more compact
|
||
|
|
// representation. The prefixes are stored on the edges of the trie, and one
|
||
|
|
// edge can represent multiple characters. For example, given two exported
|
||
|
|
// symbols _bar and _baz, we will have a trie like this (terminal nodes are
|
||
|
|
// marked with an asterisk):
|
||
|
|
//
|
||
|
|
// +-+-+
|
||
|
|
// | | // root node
|
||
|
|
// +-+-+
|
||
|
|
// |
|
||
|
|
// | _ba
|
||
|
|
// |
|
||
|
|
// +-+-+
|
||
|
|
// | |
|
||
|
|
// +-+-+
|
||
|
|
// r / \ z
|
||
|
|
// / \
|
||
|
|
// +-+-+ +-+-+
|
||
|
|
// | * | | * |
|
||
|
|
// +-+-+ +-+-+
|
||
|
|
//
|
||
|
|
// More documentation of the format can be found in
|
||
|
|
// llvm/tools/obj2yaml/macho2yaml.cpp.
|
||
|
|
//
|
||
|
|
//===----------------------------------------------------------------------===//
|
||
|
|
|
||
|
|
#include "ExportTrie.h"
|
||
|
|
#include "Symbols.h"
|
||
|
|
|
||
|
|
#include "lld/Common/ErrorHandler.h"
|
||
|
|
#include "lld/Common/Memory.h"
|
||
|
|
#include "llvm/ADT/Optional.h"
|
||
|
|
#include "llvm/BinaryFormat/MachO.h"
|
||
|
|
#include "llvm/Support/LEB128.h"
|
||
|
|
|
||
|
|
using namespace llvm;
|
||
|
|
using namespace llvm::MachO;
|
||
|
|
using namespace lld;
|
||
|
|
using namespace lld::macho;
|
||
|
|
|
||
|
|
namespace {
|
||
|
|
|
||
|
|
struct Edge {
|
||
|
|
Edge(StringRef s, TrieNode *node) : substring(s), child(node) {}
|
||
|
|
|
||
|
|
StringRef substring;
|
||
|
|
struct TrieNode *child;
|
||
|
|
};
|
||
|
|
|
||
|
|
struct ExportInfo {
|
||
|
|
uint64_t address;
|
||
|
|
uint8_t flags = 0;
|
||
|
|
ExportInfo(const Symbol &sym, uint64_t imageBase)
|
||
|
|
: address(sym.getVA() - imageBase) {
|
||
|
|
// Set the symbol type.
|
||
|
|
if (sym.isWeakDef())
|
||
|
|
flags |= EXPORT_SYMBOL_FLAGS_WEAK_DEFINITION;
|
||
|
|
// TODO: Add proper support for re-exports & stub-and-resolver flags.
|
||
|
|
|
||
|
|
// Set the symbol kind.
|
||
|
|
if (sym.isTlv()) {
|
||
|
|
flags |= EXPORT_SYMBOL_FLAGS_KIND_THREAD_LOCAL;
|
||
|
|
} else if (auto *defined = dyn_cast<Defined>(&sym)) {
|
||
|
|
if (defined->isAbsolute())
|
||
|
|
flags |= EXPORT_SYMBOL_FLAGS_KIND_ABSOLUTE;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
} // namespace
|
||
|
|
|
||
|
|
struct macho::TrieNode {
|
||
|
|
std::vector<Edge> edges;
|
||
|
|
Optional<ExportInfo> info;
|
||
|
|
// Estimated offset from the start of the serialized trie to the current node.
|
||
|
|
// This will converge to the true offset when updateOffset() is run to a
|
||
|
|
// fixpoint.
|
||
|
|
size_t offset = 0;
|
||
|
|
|
||
|
|
// Returns whether the new estimated offset differs from the old one.
|
||
|
|
bool updateOffset(size_t &nextOffset);
|
||
|
|
void writeTo(uint8_t *buf) const;
|
||
|
|
};
|
||
|
|
|
||
|
|
bool TrieNode::updateOffset(size_t &nextOffset) {
|
||
|
|
// Size of the whole node (including the terminalSize and the outgoing edges.)
|
||
|
|
// In contrast, terminalSize only records the size of the other data in the
|
||
|
|
// node.
|
||
|
|
size_t nodeSize;
|
||
|
|
if (info) {
|
||
|
|
uint32_t terminalSize =
|
||
|
|
getULEB128Size(info->flags) + getULEB128Size(info->address);
|
||
|
|
// Overall node size so far is the uleb128 size of the length of the symbol
|
||
|
|
// info + the symbol info itself.
|
||
|
|
nodeSize = terminalSize + getULEB128Size(terminalSize);
|
||
|
|
} else {
|
||
|
|
nodeSize = 1; // Size of terminalSize (which has a value of 0)
|
||
|
|
}
|
||
|
|
// Compute size of all child edges.
|
||
|
|
++nodeSize; // Byte for number of children.
|
||
|
|
for (Edge &edge : edges) {
|
||
|
|
nodeSize += edge.substring.size() + 1 // String length.
|
||
|
|
+ getULEB128Size(edge.child->offset); // Offset len.
|
||
|
|
}
|
||
|
|
// On input, 'nextOffset' is the new preferred location for this node.
|
||
|
|
bool result = (offset != nextOffset);
|
||
|
|
// Store new location in node object for use by parents.
|
||
|
|
offset = nextOffset;
|
||
|
|
nextOffset += nodeSize;
|
||
|
|
return result;
|
||
|
|
}
|
||
|
|
|
||
|
|
void TrieNode::writeTo(uint8_t *buf) const {
|
||
|
|
buf += offset;
|
||
|
|
if (info) {
|
||
|
|
// TrieNodes with Symbol info: size, flags address
|
||
|
|
uint32_t terminalSize =
|
||
|
|
getULEB128Size(info->flags) + getULEB128Size(info->address);
|
||
|
|
buf += encodeULEB128(terminalSize, buf);
|
||
|
|
buf += encodeULEB128(info->flags, buf);
|
||
|
|
buf += encodeULEB128(info->address, buf);
|
||
|
|
} else {
|
||
|
|
// TrieNode with no Symbol info.
|
||
|
|
*buf++ = 0; // terminalSize
|
||
|
|
}
|
||
|
|
// Add number of children. TODO: Handle case where we have more than 256.
|
||
|
|
assert(edges.size() < 256);
|
||
|
|
*buf++ = edges.size();
|
||
|
|
// Append each child edge substring and node offset.
|
||
|
|
for (const Edge &edge : edges) {
|
||
|
|
memcpy(buf, edge.substring.data(), edge.substring.size());
|
||
|
|
buf += edge.substring.size();
|
||
|
|
*buf++ = '\0';
|
||
|
|
buf += encodeULEB128(edge.child->offset, buf);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
TrieNode *TrieBuilder::makeNode() {
|
||
|
|
auto *node = make<TrieNode>();
|
||
|
|
nodes.emplace_back(node);
|
||
|
|
return node;
|
||
|
|
}
|
||
|
|
|
||
|
|
static int charAt(const Symbol *sym, size_t pos) {
|
||
|
|
StringRef str = sym->getName();
|
||
|
|
if (pos >= str.size())
|
||
|
|
return -1;
|
||
|
|
return str[pos];
|
||
|
|
}
|
||
|
|
|
||
|
|
// Build the trie by performing a three-way radix quicksort: We start by sorting
|
||
|
|
// the strings by their first characters, then sort the strings with the same
|
||
|
|
// first characters by their second characters, and so on recursively. Each
|
||
|
|
// time the prefixes diverge, we add a node to the trie.
|
||
|
|
//
|
||
|
|
// node: The most recently created node along this path in the trie (i.e.
|
||
|
|
// the furthest from the root.)
|
||
|
|
// lastPos: The prefix length of the most recently created node, i.e. the number
|
||
|
|
// of characters along its path from the root.
|
||
|
|
// pos: The string index we are currently sorting on. Note that each symbol
|
||
|
|
// S contained in vec has the same prefix S[0...pos).
|
||
|
|
void TrieBuilder::sortAndBuild(MutableArrayRef<const Symbol *> vec,
|
||
|
|
TrieNode *node, size_t lastPos, size_t pos) {
|
||
|
|
tailcall:
|
||
|
|
if (vec.empty())
|
||
|
|
return;
|
||
|
|
|
||
|
|
// Partition items so that items in [0, i) are less than the pivot,
|
||
|
|
// [i, j) are the same as the pivot, and [j, vec.size()) are greater than
|
||
|
|
// the pivot.
|
||
|
|
const Symbol *pivotSymbol = vec[vec.size() / 2];
|
||
|
|
int pivot = charAt(pivotSymbol, pos);
|
||
|
|
size_t i = 0;
|
||
|
|
size_t j = vec.size();
|
||
|
|
for (size_t k = 0; k < j;) {
|
||
|
|
int c = charAt(vec[k], pos);
|
||
|
|
if (c < pivot)
|
||
|
|
std::swap(vec[i++], vec[k++]);
|
||
|
|
else if (c > pivot)
|
||
|
|
std::swap(vec[--j], vec[k]);
|
||
|
|
else
|
||
|
|
k++;
|
||
|
|
}
|
||
|
|
|
||
|
|
bool isTerminal = pivot == -1;
|
||
|
|
bool prefixesDiverge = i != 0 || j != vec.size();
|
||
|
|
if (lastPos != pos && (isTerminal || prefixesDiverge)) {
|
||
|
|
TrieNode *newNode = makeNode();
|
||
|
|
node->edges.emplace_back(pivotSymbol->getName().slice(lastPos, pos),
|
||
|
|
newNode);
|
||
|
|
node = newNode;
|
||
|
|
lastPos = pos;
|
||
|
|
}
|
||
|
|
|
||
|
|
sortAndBuild(vec.slice(0, i), node, lastPos, pos);
|
||
|
|
sortAndBuild(vec.slice(j), node, lastPos, pos);
|
||
|
|
|
||
|
|
if (isTerminal) {
|
||
|
|
assert(j - i == 1); // no duplicate symbols
|
||
|
|
node->info = ExportInfo(*pivotSymbol, imageBase);
|
||
|
|
} else {
|
||
|
|
// This is the tail-call-optimized version of the following:
|
||
|
|
// sortAndBuild(vec.slice(i, j - i), node, lastPos, pos + 1);
|
||
|
|
vec = vec.slice(i, j - i);
|
||
|
|
++pos;
|
||
|
|
goto tailcall;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
size_t TrieBuilder::build() {
|
||
|
|
if (exported.empty())
|
||
|
|
return 0;
|
||
|
|
|
||
|
|
TrieNode *root = makeNode();
|
||
|
|
sortAndBuild(exported, root, 0, 0);
|
||
|
|
|
||
|
|
// Assign each node in the vector an offset in the trie stream, iterating
|
||
|
|
// until all uleb128 sizes have stabilized.
|
||
|
|
size_t offset;
|
||
|
|
bool more;
|
||
|
|
do {
|
||
|
|
offset = 0;
|
||
|
|
more = false;
|
||
|
|
for (TrieNode *node : nodes)
|
||
|
|
more |= node->updateOffset(offset);
|
||
|
|
} while (more);
|
||
|
|
|
||
|
|
return offset;
|
||
|
|
}
|
||
|
|
|
||
|
|
void TrieBuilder::writeTo(uint8_t *buf) const {
|
||
|
|
for (TrieNode *node : nodes)
|
||
|
|
node->writeTo(buf);
|
||
|
|
}
|
||
|
|
|
||
|
|
namespace {
|
||
|
|
|
||
|
|
// Parse a serialized trie and invoke a callback for each entry.
|
||
|
|
class TrieParser {
|
||
|
|
public:
|
||
|
|
TrieParser(const uint8_t *buf, size_t size, const TrieEntryCallback &callback)
|
||
|
|
: start(buf), end(start + size), callback(callback) {}
|
||
|
|
|
||
|
|
void parse(const uint8_t *buf, const Twine &cumulativeString);
|
||
|
|
|
||
|
|
void parse() { parse(start, ""); }
|
||
|
|
|
||
|
|
const uint8_t *start;
|
||
|
|
const uint8_t *end;
|
||
|
|
const TrieEntryCallback &callback;
|
||
|
|
};
|
||
|
|
|
||
|
|
} // namespace
|
||
|
|
|
||
|
|
void TrieParser::parse(const uint8_t *buf, const Twine &cumulativeString) {
|
||
|
|
if (buf >= end)
|
||
|
|
fatal("Node offset points outside export section");
|
||
|
|
|
||
|
|
unsigned ulebSize;
|
||
|
|
uint64_t terminalSize = decodeULEB128(buf, &ulebSize);
|
||
|
|
buf += ulebSize;
|
||
|
|
uint64_t flags = 0;
|
||
|
|
size_t offset;
|
||
|
|
if (terminalSize != 0) {
|
||
|
|
flags = decodeULEB128(buf, &ulebSize);
|
||
|
|
callback(cumulativeString, flags);
|
||
|
|
}
|
||
|
|
buf += terminalSize;
|
||
|
|
uint8_t numEdges = *buf++;
|
||
|
|
for (uint8_t i = 0; i < numEdges; ++i) {
|
||
|
|
const char *cbuf = reinterpret_cast<const char *>(buf);
|
||
|
|
StringRef substring = StringRef(cbuf, strnlen(cbuf, end - buf));
|
||
|
|
buf += substring.size() + 1;
|
||
|
|
offset = decodeULEB128(buf, &ulebSize);
|
||
|
|
buf += ulebSize;
|
||
|
|
parse(start + offset, cumulativeString + substring);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
void macho::parseTrie(const uint8_t *buf, size_t size,
|
||
|
|
const TrieEntryCallback &callback) {
|
||
|
|
if (size == 0)
|
||
|
|
return;
|
||
|
|
|
||
|
|
TrieParser(buf, size, callback).parse();
|
||
|
|
}
|