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[EVM] Fix lld-c api to only perform extracting .text section from an …
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…object file.
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@PavelKopyl
PavelKopyl committed Jun 6, 2024
1 parent 62e74e2 commit bfe2316
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Showing 2 changed files with 10 additions and 159 deletions.
4 changes: 2 additions & 2 deletions lld/include/lld-c/LLDAsLibraryC.h
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Original file line number Diff line number Diff line change
Expand Up @@ -26,8 +26,8 @@ LLVMBool LLVMLinkMemoryBuffers(LLVMMemoryBufferRef *inMemBufs, size_t numInBufs,
LLVMMemoryBufferRef *outMemBuf,
const char **lldArgs, size_t numLldArgs);

LLVMBool LLVMLinkEVM(LLVMMemoryBufferRef inMemBufs[], const char *inMemBufIDs[],
size_t numInBufs, LLVMMemoryBufferRef outMemBuf[2]);
LLVMBool LLVMLinkEVM(LLVMMemoryBufferRef inMemBuf,
LLVMMemoryBufferRef *outMemBuf);
LLVM_C_EXTERN_C_END

#endif // LLD_C_LLDASLIBRARYC_H
165 changes: 8 additions & 157 deletions lld/lld-c/LLDAsLibraryC.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -33,152 +33,15 @@ LLVMBool LLVMLinkMemoryBuffers(LLVMMemoryBufferRef *inMemBufs, size_t numInBufs,
return !s.retCode && s.canRunAgain;
}

/// This function generates a linker script for EVM architecture.
/// \p memBufs - array of input memory buffers with following structure:
///
/// memBufs[0] - deploy object code
/// memBufs[1] - deplyed object code
/// --------------------------
/// memBufs[2] - 1-st sub-contract (final EVM bytecode)
/// ...
/// memBufs[N] - N-st sub-contract (final EVM bytecode)
///
/// Sub contracts are optional. They should have the same ordering as in
/// the YUL layout.
///
/// \p bufIDs - array of string identifiers of the buffers. IDs correspond
/// to the object names in the YUL layout.
///
/// For example, the YUL object:
///
/// |--D_105_deploy --||--D_105_deployed --||-- B_40 --|
///
/// __datasize_B_40 = 1384;
/// SECTIONS {
/// . = 0;
/// .text : SUBALIGN(1) {
/// D_105(.text);
/// __dataoffset_D_105_deployed = .;
/// D_105_deployed(.text);
/// __datasize_D_105_deployed = . - __dataoffset_D_105_deployed;
/// __dataoffset_B_40 = .;
/// __datasize_D_105 = __dataoffset_B_40 + __datasize_B_40;
/// QUAD(__dataoffset_D_105_deployed);
/// }
///
/// The dot '.' denotes current location in the resulting file.
/// The purpose of the script is to define datasize/dataoffset absolute symbols
/// that reflect the YUL layour.
static std::string
creteEVMLinkerScript(llvm::ArrayRef<LLVMMemoryBufferRef> memBufs,
llvm::ArrayRef<const char *> bufIDs) {
assert(memBufs.size() == bufIDs.size());
llvm::Twine dzPrefix("__datasize_");
llvm::Twine dfPrefix("__dataoffset_");
LLVMBool LLVMLinkEVM(LLVMMemoryBufferRef inMemBuf,
LLVMMemoryBufferRef *outMemBuf) {
llvm::SmallVector<llvm::MemoryBufferRef> localInMemBufRefs(1);
localInMemBufRefs[0] = *llvm::unwrap(inMemBuf);

// Define the script part related to top-level contract.
llvm::StringRef topName(bufIDs[0]);
llvm::StringRef deploy = topName;
llvm::StringRef deployed(bufIDs[1]);

llvm::Twine topLevel = deploy + "(.text);\n" + dfPrefix + deployed +
" = .;\n" + deployed + "(.text);\n" + dzPrefix +
deployed + " = . - " + dfPrefix + deployed + ";\n";

std::string symDatasizeDeps;
std::string symDataOffsetDeps;
if (memBufs.size() > 2) {
// Define datasize symbols for the dependent contracts. They start after
// {deploy, deployed} pair of the top-level contract,.i.e. at index 2.
for (unsigned idx = 2; idx < bufIDs.size(); ++idx)
symDatasizeDeps += (dzPrefix + bufIDs[idx] + " = " +
llvm::Twine(LLVMGetBufferSize(memBufs[idx])) + ";\n")
.str();

// Define dataoffset symbols for the dependent contracts.
symDataOffsetDeps = (dfPrefix + bufIDs[2] + " = .;\n").str();
for (unsigned idx = 3; idx < bufIDs.size(); ++idx) {
symDataOffsetDeps +=
(dfPrefix + bufIDs[idx] + " = " + dfPrefix + bufIDs[idx - 1] + " + " +
dzPrefix + bufIDs[idx - 1] + ";\n")
.str();
}
}

// Define datasize symbol for top-level contract.
std::string symDatasizeTop = (dzPrefix + topName + " = ").str();
if (memBufs.size() > 2)
symDatasizeTop +=
(dfPrefix + bufIDs.back() + " + " + dzPrefix + bufIDs.back() + ";\n")
.str();
else
symDatasizeTop += ".;\n";

// Emit size of the deploy code as an 8-byte usingned integer.
llvm::Twine deploySize = "QUAD(" + dfPrefix + deployed + ");\n";

llvm::Twine script = llvm::formatv(
"{0}\n\
SECTIONS {\n\
. = 0;\n\
.text : SUBALIGN(1) {\n\
{1}\
{2}\
{3}\
{4}\
}\n\
}\n\
",
symDatasizeDeps, topLevel, symDataOffsetDeps, symDatasizeTop, deploySize);

return script.str();
}

LLVMBool LLVMLinkEVM(LLVMMemoryBufferRef inMemBufs[], const char *inMemBufIDs[],
size_t numInBufs, LLVMMemoryBufferRef outMemBuf[2]) {
assert(numInBufs > 1);
// Define local copies of the IN buffers. FIXME: we can avoid this and also
// get rig of inMemBufIDs, but this requires that a proper name is set up in
// each memory buffer.
llvm::SmallVector<llvm::MemoryBufferRef> localInMemBufRefs(3);
llvm::SmallVector<std::unique_ptr<llvm::MemoryBuffer>> localInMemBufs(3);
for (unsigned idx = 0; idx < 2; ++idx) {
llvm::MemoryBufferRef Ref = *llvm::unwrap(inMemBufs[idx]);
localInMemBufs[idx] =
llvm::MemoryBuffer::getMemBuffer(Ref.getBuffer(), inMemBufIDs[idx],
/*RequiresNullTerminator*/ false);
localInMemBufRefs[idx] = localInMemBufs[idx]->getMemBufferRef();
}

std::string linkerScript =
creteEVMLinkerScript(llvm::ArrayRef(inMemBufs, numInBufs),
llvm::ArrayRef(inMemBufIDs, numInBufs));
std::cerr << linkerScript << "\n";
std::unique_ptr<llvm::MemoryBuffer> ScriptBuf =
llvm::MemoryBuffer::getMemBuffer(linkerScript, "script.x");
localInMemBufRefs[2] = ScriptBuf->getMemBufferRef();

llvm::SmallVector<const char *, 16> lldArgs;
llvm::SmallVector<const char *, 8> lldArgs;
lldArgs.push_back("ld.lld");

lldArgs.push_back("-T");
lldArgs.push_back("script.x");

// Use remapping of file names (a linker feature) to replace file names with
// indexes in the array of memory buffers.
llvm::Twine remapStr("--remap-inputs=");
std::string remapDeployStr = (remapStr + inMemBufIDs[0] + "=0").str();
lldArgs.push_back(remapDeployStr.c_str());

std::string remapDeployedStr = (remapStr + inMemBufIDs[1] + "=1").str();
lldArgs.push_back(remapDeployedStr.c_str());

lldArgs.push_back("--remap-inputs=script.x=2");

// Deploy code
lldArgs.push_back(inMemBufIDs[0]);
// Deployed code
lldArgs.push_back(inMemBufIDs[1]);
lldArgs.push_back("0");

lldArgs.push_back("--oformat=binary");

Expand All @@ -192,19 +55,7 @@ LLVMBool LLVMLinkEVM(LLVMMemoryBufferRef inMemBufs[], const char *inMemBufIDs[],
return isOK;

llvm::StringRef data = ostream.str();
// Linker script adds size of the deploy code as a 8-byte BE unsigned to the
// end of .text section. Knowing this, we can extract final deploy and
// deployed codes.
assert(data.size() > 8);
size_t deploySize =
llvm::support::endian::read64be(data.data() + data.size() - 8);
assert(deploySize < data.size());
size_t deployedSize = data.size() - deploySize - 8;

outMemBuf[0] = LLVMCreateMemoryBufferWithMemoryRangeCopy(
data.data(), deploySize, "deploy");
outMemBuf[1] = LLVMCreateMemoryBufferWithMemoryRangeCopy(
data.data() + deploySize, deployedSize, "deployed");

*outMemBuf = LLVMCreateMemoryBufferWithMemoryRangeCopy(data.data(),
data.size(), "result");
return isOK;
}

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