Readelf: add -z decompression support

[tig_freebsdfoundation.org]

Summary

Add decompress section function for readelf.
Update Makefile.
Update readelf.1
Depends on this libelf patch

Test Plan

Compared results with/without -z flags.
Confirmed -h prints -z usage info.
Compared results for:

readelf -x [section] -z file
readelf -p [section] -z file

with GNU's readelf.

diff elftoolchain_output gnu_output

shows no difference.

[markj]

The readelf man page needs to be updated to mention the new option.

contrib/elftoolchain/readelf/readelf.c

6915

The brace should be on a separate line.

7020

buf needs to be freed after we're done with it, but only if it's not equal to d->d_buf.

7746

-z needs to be documented in this usage string.

[emaste]

libelf committed in rS366977

[tig_freebsdfoundation.org]

contrib/elftoolchain/readelf/readelf.c

7020

Since buf pointer keeps moving I added a pointer to newly allocated decompressed buffer.
If it's not null, we set buf = new_buf and free it after a section is processed.

[emaste]

contrib/elftoolchain/readelf/readelf.c

6841

we can use bool and return true / false

6843–6847

FreeBSD style(9) wants doesn't use this style; should be

/*
 * Decompress a data section if needed (using ZLIB).
 * Returns 0 if sucessful, 1 otherwise.
 */
static int decompress_section(struct section *s, 
    unsigned char *compressed_data_buffer, uint64_t compressed_size, 
    unsigned char **ret_buf, uint64_t *ret_sz)
{

6851–6853

these should be indented by 1/2 tabs

6892–6894

{} are not required for single-statement bodies. They are permitted but need to be consistent throughout and they're not used elsewhere

[markj]

contrib/elftoolchain/readelf/readelf.1

161

Shouldn't it be Fl z | Fl -decompress?

164

"specified by .Fl x or .Fl p"

contrib/elftoolchain/readelf/readelf.c

7109

new_buf is uninitialized if (re->options & RE_Z) == 0.

[tig_freebsdfoundation.org]

contrib/elftoolchain/readelf/readelf.c

7109

Fixed by setting new_buf to NULL every loop.

[markj]

contrib/elftoolchain/readelf/readelf.c

6953

The indentation is wonky.

6973

Please avoid indenting goto labels.

7048

free(NULL) is fine, there's no need to check for NULL.

7111

Ditto.