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[lld-macho] check minimum header length when opening linkable input files

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Bifurcate the `readFile()` API into ...
* `readRawFile()` which performs no checks, and
* `readLinkableFile()` which enforces minimum length of 20 bytes, same as ld64

There are no new tests because tweaks to existing tests are sufficient.

Differential Revision: https://reviews.llvm.org/D97610
This commit is contained in:
Greg McGary
2021-02-26 23:28:52 -08:00
parent e0b1df924a
commit 0223ab035c
6 changed files with 53 additions and 12 deletions
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26
lld/MachO/InputFiles.cpp
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@@ -91,7 +91,8 @@ std::unique_ptr<TarWriter> macho::tar;
int InputFile::idCount = 0;
// Open a given file path and return it as a memory-mapped file.
Optional<MemoryBufferRef> macho::readFile(StringRef path) {
// Perform no sanity checks--just open, map & return.
Optional<MemoryBufferRef> macho::readRawFile(StringRef path) {
// Open a file.
auto mbOrErr = MemoryBuffer::getFile(path);
if (auto ec = mbOrErr.getError()) {
@@ -102,6 +103,27 @@ Optional<MemoryBufferRef> macho::readFile(StringRef path) {
std::unique_ptr<MemoryBuffer> &mb = *mbOrErr;
MemoryBufferRef mbref = mb->getMemBufferRef();
make<std::unique_ptr<MemoryBuffer>>(std::move(mb)); // take mb ownership
return mbref;
}
// Open a given file path and return it as a memory-mapped file.
// Assume the file has one of a variety of linkable formats and
// perform some basic sanity checks, notably minimum length.
Optional<MemoryBufferRef> macho::readLinkableFile(StringRef path) {
Optional<MemoryBufferRef> maybeMbref = readRawFile(path);
if (!maybeMbref) {
return None;
}
MemoryBufferRef mbref = *maybeMbref;
// LD64 hard-codes 20 as minimum header size, which is presumably
// the smallest header among the the various linkable input formats
// LLD are less demanding. We insist on having only enough data for
// a magic number.
if (mbref.getBufferSize() < sizeof(uint32_t)) {
error("file is too small to contain a magic number: " + path);
return None;
}
// If this is a regular non-fat file, return it.
const char *buf = mbref.getBufferStart();
@@ -544,7 +566,7 @@ void ObjFile::parseDebugInfo() {
// The path can point to either a dylib or a .tbd file.
static Optional<DylibFile *> loadDylib(StringRef path, DylibFile *umbrella) {
Optional<MemoryBufferRef> mbref = readFile(path);
Optional<MemoryBufferRef> mbref = readLinkableFile(path);
if (!mbref) {
error("could not read dylib file at " + path);
return {};