std::string JITDebugRegisterer::MakeELF(const Function *F, DebugInfo &I) {
// Stack allocate an empty module with an empty LLVMContext for the ELFWriter
// API. We don't use the real module because then the ELFWriter would write
// out unnecessary GlobalValues during finalization.
LLVMContext Context;
Module M("", Context);
// Make a buffer for the ELF in memory.
std::string Buffer;
raw_string_ostream O(Buffer);
ELFWriter EW(O, TM);
EW.doInitialization(M);
// Copy the binary into the .text section. This isn't necessary, but it's
// useful to be able to disassemble the ELF by hand.
ELFSection &Text = EW.getTextSection(const_cast<Function *>(F));
Text.Addr = (uint64_t)I.FnStart;
// TODO: We could eliminate this copy if we somehow used a pointer/size pair
// instead of a vector.
Text.getData().assign(I.FnStart, I.FnEnd);
// Copy the exception handling call frame information into the .eh_frame
// section. This allows GDB to get a good stack trace, particularly on
// linux x86_64. Mark this as a PROGBITS section that needs to be loaded
// into memory at runtime.
ELFSection &EH = EW.getSection(".eh_frame", ELF::SHT_PROGBITS,
ELF::SHF_ALLOC);
// Pointers in the DWARF EH info are all relative to the EH frame start,
// which is stored here.
EH.Addr = (uint64_t)I.EhStart;
// TODO: We could eliminate this copy if we somehow used a pointer/size pair
// instead of a vector.
EH.getData().assign(I.EhStart, I.EhEnd);
// Add this single function to the symbol table, so the debugger prints the
// name instead of '???'. We give the symbol default global visibility.
ELFSym *FnSym = ELFSym::getGV(F,
ELF::STB_GLOBAL,
ELF::STT_FUNC,
ELF::STV_DEFAULT);
FnSym->SectionIdx = Text.SectionIdx;
FnSym->Size = I.FnEnd - I.FnStart;
FnSym->Value = 0; // Offset from start of section.
EW.SymbolList.push_back(FnSym);
EW.doFinalization(M);
O.flush();
// When trying to debug why GDB isn't getting the debug info right, it's
// awfully helpful to write the object file to disk so that it can be
// inspected with readelf and objdump.
if (JITEmitDebugInfoToDisk) {
std::string Filename;
raw_string_ostream O2(Filename);
O2 << "/tmp/llvm_function_" << I.FnStart << "_" << F->getNameStr() << ".o";
O2.flush();
std::string Errors;
raw_fd_ostream O3(Filename.c_str(), Errors);
O3 << Buffer;
O3.close();
}
return Buffer;
}
/*
* Hash OIDs
*
* SHA1 = 1.3.14.3.2.26
* MDx = 1.2.840.113549.2.x
*/
#define O0(a,b) ((a)*40+(b))
#define O2(x) \
(((x)>>7)&0x7F)|0x80, \
((x)&0x7F)
#define O3(x) \
(((x)>>14)&0x7F)|0x80, \
(((x)>>7)&0x7F)|0x80, \
((x)&0x7F)
uchar oidsha1[] = { O0(1, 3), 14, 3, 2, 26 };
uchar oidmd2[] = { O0(1, 2), O2(840), O3(113549), 2, 2 };
uchar oidmd5[] = { O0(1, 2), O2(840), O3(113549), 2, 5 };
/*
* DigestInfo ::= SEQUENCE {
* digestAlgorithm AlgorithmIdentifier,
* digest OCTET STRING
* }
*
* except that OpenSSL seems to sign
*
* DigestInfo ::= SEQUENCE {
* SEQUENCE{ digestAlgorithm AlgorithmIdentifier, NULL }
* digest OCTET STRING
* }
*
