Re: [PATCH][RFC] readelf: partial support of ZSTD compression

[Mark Wielaard <mark@klomp.org>]

Hi Martin,

On Mon, Nov 28, 2022 at 02:16:35PM +0100, Martin Liška wrote:
> On 10/29/22 00:21, Mark Wielaard wrote:
> > Although I like to also have compression working.  Then we can also
> > add support to src/elfcompress, which makes for a good testcase. See
> > tests/run-compress.sh (which has found some subtle memory issues when
> > run under valgrind).
> 
> All right, so I'm preparing a full support for ZSTD (both compression and compression)
> and I noticed a refactoring would be handy for compress_section function and callers
> of the function.
> 
> Note right now, there are basically 3 compression types and process_file
> function handles basically all combinations of these (3 x 3 options), while adding ZSTD
> support would make it even more complicated. However, ZSTD will behave very similar to ZLIB
> (not zlib-gnu), except a different algorithm will be used. Plus, in order to distinguish
> ZLIB from ZSTD, we need to read GElf_Chdr.
> 
> So what do you think about the refactoring as the first step?

Looks good. I would just add a sanity check that chdr.ch_type is of a
known compression type (it is only checked to be not NONE atm).

Cheers,

Mark