Re: gs_group_1 crashing on 13beta2/s390x

Hi,

Christoph helped me to get access to a s390x machine - I wasn't able to
reproduce exactly the error he hit. Initially all tests passed, but
after recompiling with build flags more similar to Christop's I was able
to hit another instance of what I assume to be the same bug.

I am fairly sure that I see the problem. Before a post LLVM 10 change
the "runtime linker" for JITed code only asserted that relocations that
need to be performed are of a known type. Since the debian build -
correctly - uses a release version of LLVM, this results in unhandled
relocations basically being resolved to 0.

I suspect that building with LDFLAGS="-Wl,-z,relro -Wl,-z,now" - which
is what I think the debian package does - creates the types of
relocations that LLVM doesn't handle for elf + s390.

10 release branch:

void RuntimeDyldELF::resolveSystemZRelocation(const SectionEntry &Section,
                                              uint64_t Offset, uint64_t Value,
                                              uint32_t Type, int64_t Addend) {
  uint8_t *LocalAddress = Section.getAddressWithOffset(Offset);
  switch (Type) {
  default:
    llvm_unreachable("Relocation type not implemented yet!");
    break;

11/master:

void RuntimeDyldELF::resolveSystemZRelocation(const SectionEntry &Section,
                                              uint64_t Offset, uint64_t Value,
                                              uint32_t Type, int64_t Addend) {
  uint8_t *LocalAddress = Section.getAddressWithOffset(Offset);
  switch (Type) {
  default:
    report_fatal_error("Relocation type not implemented yet!");
    break;

Verifying that that's the case by rebuilding against 11 (and then an
LLVM debug build, which will take a day or two).

Greetings,

Andres Freund