[llvm-dev] [RFC] Support disassembly of ARM and thumb mixed in single ELF file

[Michael Spencer via llvm-dev]

On Fri, Sep 16, 2016 at 2:51 PM, Hemant Kulkarni <khemant at codeaurora.org>
wrote:

> Hi,
>
>
>
> The llvm-objdump tool at the moment disassembles ARM ELF binary but with
> lot of extra user supplied data
>
> ·         The triple supplied on the command line for tools has to be be
> correct (ARM, thumb etc)
>
> ·         The ELF file cannot have mix of ARM and thumb
>
> ·         There is no direct way of using it such as llvm-objdump –d
> elf_file. This works for architectures such as Hexagon, X86 etc.
>
>
>
> Is there a way to enhance the tool to make the use more friendly by
> removing the need to specify these extra option on command line since it is
> possible to find the information in the file.
>
> The ELF file for arm does not have any field that can be easily inspected
> to see if the file of type ET_ARM is either a thumb only binary, ARM only
> binary or a mix. There is however an optional ARM specific section
> .ARM.attributes that can contain CPU and architecture information such as
> ISA in use. BFD and gold linker use this section while linking to find any
> incompatibilities and then emit out a merged (as per ARM ABI extensions)
> section in final binary.
>
>
>
> Any ideas to add this functionality to the without completely redesigning
> the llvm-objdump will be appreciated. There is already a patch that uses
> data from ELF file to try doing this.
>
> It is at https://reviews.llvm.org/D24636
>
>
>
> Thanks,
>
>
>
objdump is currently in a pretty bad state. The disassembler was basically
ripped from llvm-mc and has been hacked on since without needed
refactoring. I feel that at this point we need to stop and restructure it
before throwing more complexity onto the pile.

- Michael Spencer
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