[LLVMdev] Assertions in RuntimeDyldELF in ExecutionEngine/MCJIT tests

[Alexey Samsonov]

Hi Andrew,

Looks like RecordingMemoryManager in lli just calls malloc() and it would
be strange to make assumptions (or enforce) that the difference between two
returned pointers in 64-bit
virtual address space will be fit into 32 bits. Can we do smth similar to
what Adhemerval proposed (see the special case in processRelocationRef for
ELF::R_PPC64_REL24 relocations)?


On Tue, Jan 29, 2013 at 9:40 PM, Kaylor, Andrew <andrew.kaylor at intel.com>wrote:

>  Hi Alexey,****
>
> ** **
>
> I think the most likely way to resolve this is to have the
> RecordingMemoryManager do something more complex to manage its allocations
> in such a way as to guarantee that they are all within proximity of one
> another.  The code that is asserting is handling a relocation where code
> was generated to use a 32-bit relative offset in 64-bit code.  If the two
> sections involved really are more than a 32-bit offset apart then the
> generated code will not work.****
>
> ** **
>
> Alternatively, we could have MCJIT use whatever code generation option
> will prevent 32-bit relative relocations from being generated in the first
> place.  That would probably be preferable, but I haven’t had success trying
> to do that in limited efforts up to now.****
>
> ** **
>
> As it happens, I’m working with the ‘-use-remote’ option for lli this week
> trying to add support for actual out-of-process execution.  As I do, I’ll
> take a look at the allocation scheme in RecordingMemoryManager and see if
> there is something reasonable I can do there.****
>
> ** **
>
> In the meantime, is there any way that you can mark these tests as XFAIL
> in the sanitizer case?****
>
> ** **
>
> Thanks,****
>
> Andy****
>
> ** **
>
> *From:* Alexey Samsonov [mailto:samsonov at google.com]
> *Sent:* Tuesday, January 29, 2013 3:36 AM
> *To:* LLVM Developers Mailing List
> *Cc:* Kaylor, Andrew
> *Subject:* Assertions in RuntimeDyldELF in ExecutionEngine/MCJIT tests****
>
> ** **
>
> Hi!****
>
> ** **
>
> I'm trying to run LLVM test suite under AddressSanitizer and get test
> failures in:****
>
>     LLVM :: ExecutionEngine/MCJIT/simpletest-remote.ll****
>
>     LLVM :: ExecutionEngine/MCJIT/test-data-align-remote.ll****
>
>     LLVM :: ExecutionEngine/MCJIT/test-fp-no-external-funcs-remote.ll****
>
>     LLVM :: ExecutionEngine/MCJIT/test-global-init-nonzero-remote.ll****
>
> ** **
>
> All of them fail with assertion:****
>
> lli:
> /usr/local/google/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp:230:
> void llvm::RuntimeDyldELF::resolveX86_64Relocation(const llvm::SectionEntry
> &, uint64_t, uint64_t, uint32_t, int64_t): Assertion `RealOffset <=
> (2147483647) && RealOffset >= (-2147483647-1)' failed.****
>
> ** **
>
> The reason is that AddressSanitizer replaces system malloc with its own
> allocator, which****
>
> allocates memory at "unusual" parts of heap and the difference between
> pointers can be significant****
>
> (and doesn't fit in 32 bytes).****
>
> ** **
>
> I add debug output to calculation of RealOffset in resolveX86_64Relocation:
> ****
>
> ** **
>
>     uint64_t  FinalAddress = Section.LoadAddress + Offset;****
>
>     int64_t RealOffset = *Placeholder + Value + Addend - FinalAddress;****
>
>     fprintf(stderr, "%x + %lx + %lx - %lx = %lx\n",****
>
>             *Placeholder, Value, Addend, FinalAddress, RealOffset);****
>
>     assert(RealOffset <= INT32_MAX && RealOffset >= INT32_MIN);****
>
> ** **
>
> ** **
>
> This is what I get for system malloc:****
>
> ** **
>
> 0 + 7fec9867a000 + 0 - 7fec9867a040 = ffffffffffffffc0****
>
> This is what I get for ASan allocator (which results in assert failure):**
> **
>
> ** **
>
> 0 + 600c0000a8a0 + 0 - 6018000090a0 = fffffff400001800****
>
>   ** **
>
> --****
>
> Alexey Samsonov, MSK****
>



-- 
Alexey Samsonov, MSK
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