Re: [Elftoolchain-developers] Support for "in-place" updates to ELF objects has been added to libelf

[Eric S. <sch...@gm...>]

Eric Schulte <sch...@gm...> writes:

> Joseph Koshy <jk...@us...> writes:
>
>> e.s> Would it be possible to share a simple C script which opens, edits and
>> e.s> then writes out a modified elf file using libelf?
>>
>> There are a few such examples in libelf's test suite; please look for
>> the constant "ELF_C_RDWR" in:
>>
>>     http://sourceforge.net/apps/trac/elftoolchain/browser/trunk/test/libelf/tset/elf_update/update.m4
>>
>
> Thanks for the pointer.  Attached is my attempt to re-write one of the
> test cases into an external C file to allow extending a data section in
> an existing elf file.  The resulting script fails with the following...
>
>   $ ./extend-a-section hello
>   fstat() failed: "Bad address".
>   Size error: expected=118, elf_update()=6536
>
> I imagine that I broke something while replacing the TC_* macros with C
> code.  I apologize for asking such a simple question, but would you mind
> taking a look to see if the error is obvious to you.
>

Along the same lines the following script reads an elf file and then
writes it back out without making any changes.  Despite running
successfully and throwing no errors the resulting re-written file does
segfaults.