[llvm] r188022 - [Object] Split the ELF interface into 3 parts.

[Michael Spencer]

On Mon, Aug 12, 2013 at 9:32 AM, Renato Golin <renato.golin at linaro.org>wrote:

> On 12 August 2013 15:11, Renato Golin <renato.golin at linaro.org> wrote:
>
>> Looks like an error on the way it's resolving the ARM relocations on
>> MCJIT for the global constructors:
>>
>
> Michael,
>
> So, below is the debug trace with some info. I don't understand much
> what's going on, so I'll just walk through the debug result. I can give you
> access to my Chromebook and work with you to solve this problem, let me
> know if you need anything.
>
> If you feel we'll need more investigation, maybe we should revert the
> patch temporarily to keep the bots green, and re-commit when this problem
> is fixed.
>
>
> No, on to the problem...
>
> The simple ctor/dtor module gets loaded and need to resolve the
> relocations:
>
> llvm::RuntimeDyldImpl::resolveRelocationList()
>
>   For each loaded section (Address != 0), call: resolveRelocation(RE,
> Value);
>   Our section is:
>
> (gdb) p Section
> $9 = (const llvm::SectionEntry &) @0xdb9d48: {Name = {static npos =
> 4294967295, Data = 0xdb5b1d ".init_array", Length = 11},
>   Address = 0x76fdf004 "", Size = 4, LoadAddress = 1996353540, StubOffset
> = 4, ObjAddress = 0}
>
> Note that the address is not null, but the ObjAddress is.
>
> Down there, on llvm::RuntimeDyldELF::resolveARMRelocation():
>
> 404  // Write a 32bit value to relocation address, taking into account the
> 405  // implicit addend encoded in the target.
> 406  case ELF::R_ARM_TARGET1:
> 407  case ELF::R_ARM_ABS32:
> 408    *TargetPtr = *Placeholder + Value;
> 409    break;
>
> Where:
>
>   uint32_t *Placeholder = reinterpret_cast<uint32_t*>(Section.ObjAddress +
>                                                       Offset);
>
> Since the ObjAddress is 0, *Placeholder segfaults.
>
> cheers,
> --renato
>

Yeah, I'll need access to an arm machine to debug this.

- Michael Spencer
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20130812/6f2bb874/attachment.html>