Hi Mike,
On 18 November 2016 at 19:25, Mike Frysinger <vapier@xxxxxxxxxx> wrote:
> On 18 Nov 2016 08:25, Michael Kerrisk (man-pages) wrote:
>> On 11/17/2016 09:59 PM, Mike Frysinger wrote:
>> > for documenting the Elf{32,64}_Nhdr structure,
>> > the sections/segments that contain notes, and how to interpret them. I've
>> > been lazy and only included the GNU extensions here,
>>
>> Any chance you include the non-GNU stuff also? Or, failing that,
>> some clear statements at appropriate points about what is not
>> documented.
>
> the trouble i was running into is that the man pages says it documents
> the elf.h header, but the one installed by glibc doesn't have defines
> for all the non-GNU stuff. so if i put in details about the FreeBSD
> namespace, it'll have defines like NT_FREEBSD_THRMISC. none of those
> show up in the current elf.h though so people will get errors.
>
> i'm fine with that though if you are.
Actually, it sounds like your original approach is best then.
>> > +Note sections contain a series of notes (see the structs below).
>> > +Each note is followed by the name field (whose length is defined in
>> > +\fIn_namesz\fR) and then by the desc field (whose length is defined in
>> > +\fIn_descsz\fR).
>>
>> I think this could be a little clearer. I presume that the way things look is
>>
>> struct {} Nhdr
>> <name>\0
>> <desc>\0
>>
>> ?
>
> i don't think desc is NUL terminated, but otherwise, yes.
>
>> Maybe shos something like that in the text?
>
> i couldn't find any precedent to copy :). i didn't want to put it into
> the struct def since those fields aren't in the struct, they're implicit
> in memory.
>
> how about i put a small snippet of C that'd show how to extract things ?
>
> void *memory, *name, *desc;
> Elf64_Nhdr *note, *next_note;
>
> note = memory;
> name = note->n_namesz == 0 ? NULL : memory + sizeof(*note);
> desc = note->n_descsz == 0 ? NULL : name + note->n_namesz;
> next_note = memory + sizeof(*note) + note->n_namesz + note->n_descsz;
Yes, that's better than my idea.
>> > +Keep in mind that the interpretation of
>> > +.I n_type
>> > +depends on the namespace defined by the
>> > +.I n_namesz
>> > +field.
>> > +After, of course, whether the ELF image has been determined to be a core.
>>
>> I can't understand that last sentence...
>
> i meant that the namespaces are for non-core files, but i'll double check
> that is the case.
Just to be clear, the reason I could not understand that sentence was
that there appear to be some words missing.
> i snipped all the comments that i'll integrate so i don't have to just
> keep saying "OK" over and over :).
OK.
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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