.note.tag, readelf and dsynth version detection

[Matthew Dillon]

I pushed a hack to dsynth to use the second field if the first is zero,
please test.

-Matt

On Mon, Jan 27, 2020 at 5:05 PM Matthew Dillon <dillon at backplane.com> wrote:

> Hmm.  that's a good point.  It does look like a repeated structure.  I
> will look into it.
>
> -Matt
>
> On Mon, Jan 27, 2020 at 4:15 PM Romick <yellowrabbit2010 at gmail.com> wrote:
>
>> I was probably lucky :) Of course, I could be wrong, but it seems to me
>> that these pieces are not "fields" of the same structure, these are fields
>> that belong to two records in the file. Is the order of these records
>> guaranteed?
>>
>> I mean, it’s possible if I rebuild the world now, the linker will arrange
>> these records in a different order and everything will be fine, or maybe
>> not :)
>>
>> On Mon, Jan 27, 2020 at 03:56:25PM -0800, Matthew Dillon wrote:
>> > That's ... weird.  the 'zero' and the 'version' fields are transposed.
>> Are you
>> > compiling in any special way?   I've tested -release and -master on a
>> bunch of
>> > boxes and they all have the version in the right spot.
>> >
>> > -Matt
>> >
>> > On Mon, Jan 27, 2020 at 1:45 PM Romick <yellowrabbit2010 at gmail.com>
>> wrote:
>> >
>> >     Hello,
>> >     It seems that dsynth defines the system version based on the
>> .note.tag(s)
>> >     in
>> >     /bin/sh and a necessary condition is that these entries follow in a
>> >     certain order.  On my system this is not so :)
>> >
>> >     ==========
>> >     rabbit at fly ~% readelf -x .note.tag /bin/sh
>> >
>> >     Hex dump of section '.note.tag':
>> >       0x00400218 0a000000 04000000 20000000 44726167 ........ ...Drag
>> >       0x00400228 6f6e466c 79000000 00000000 0a000000 onFly...........
>> >       0x00400238 04000000 01000000 44726167 6f6e466c ........DragonFl
>> >       0x00400248 79000000 e5a30700                   y.......
>> >
>> >     rabbit at fly ~%
>> >     ==========
>> >
>> >     === /usr/src/usr.bin/dsynth/config.c ===
>> >     struct NoteTag {
>> >             Elf_Note note;
>> >             char osname1[12];
>> >             int version;            /* e.g. 500702 -> 5.7 */
>> >             int x1;
>> >             int x2;
>> >             int x3;
>> >             char osname2[12];
>> >             int zero;
>> >     };
>> >     ========================================
>> >
>> >     --
>> >       with best regards,
>> >       Yellow Rabbit @yrabbit at mastodon.sdf.org
>> >       DragonFly 5.7-DEVELOPMENT x86_64
>> >
>>
>> --
>>   with best regards,
>>   Yellow Rabbit @yrabbit at mastodon.sdf.org
>>   DragonFly 5.7-DEVELOPMENT x86_64
>>
>
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