[llvm-dev] Broken relocation for generating offsets?

[Reid Kleckner via llvm-dev]

I wouldn't be surprised if JITing COFF files on Windows doesn't work so
well, since the object file format assumes most symbols are dllimport or
within the local 2GB module address range.

I'm not familiar with the current JIT state of the art, though.


On Thu, Mar 22, 2018 at 1:45 AM via llvm-dev <llvm-dev at lists.llvm.org>
wrote:

> Hello,
>
> I append another clue I found out: The problem is definitely not caused by
> "__ImageBase" the problem comes with the "OFFSET". I generated another
> object file which crashed. The commonality:
> mov         edx, DWORD PTR ?normalPlanschbecken@@3HA ; normalPlanschbecken
> lea         rcx, *OFFSET FLAT*:??_C at _0CC@LCMJAIPO
> @Reading?5?$CCnormalPlanschbecken?$CC?5?$CFi@
> jmp         printf
>
>
>
>
> From:        via llvm-dev <llvm-dev at lists.llvm.org>
> To:        llvm-dev at lists.llvm.org
> Date:        06.03.2018 10:45
> Subject:        [llvm-dev] Broken relocation for generating offsets?
> Sent by:        "llvm-dev" <llvm-dev-bounces at lists.llvm.org>
> ------------------------------
>
>
>
> Hello LLVM-Mailing-List,
>
> I discovered a strange behavior when dealing with object files generated
> by the compiler of Visual Studio 2015.
>
> When jitting bc files I also add object files to look up functions. These
> object files are coming from visual studio. When using a switch case
> instruction that compiler often generates code based of __ImageBase. I show
> you a short snippet of the assembly output.
> mov         eax, DWORD PTR ?myInt@@3HA ; myInt
> lea         rdi,* OFFSET FLAT*:__ImageBase
> xor         ebx, ebx
>
>
>
> Then these offset is used to jump to some labels like "$LL4 at execute:".
>
> When the object file gets added to the jitting process this offset
> generation seems to be broken. Executing the code coming from the object
> file will lead to a crash. The crash address will always be exactly the
> address I used to overload __ImageBase with. So it seems that the address
> relocation is wrong with generating offsets?
>
> Kind regards
> Björn
>
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> Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode,
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>
>
>
> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
> USt.ID-Nr. DE 114 165 789
> Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode,
> Heiko Lampert, Hiroshi Kawamura, Takashi Nagano, Takeshi Fukushima.
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