libprocstat(3): retrieve process command line args and environment

[Mikolaj Golub]

On Thu, Mar 28, 2013 at 12:51:34PM +0200, Konstantin Belousov wrote:

> In the generic Elf 64bit draft specification I have, the notes sections
> are specified to consists of entries, each of which is an array of 8-byte
> words. I think we are right using the 8-byte alignment.

I have impression many implementations use 4-byte alignment. E.g. in
NetBSD:

sys/kern/core_elf32.c:

#define ELFROUNDSIZE    4       /* XXX Should it be sizeof(Elf_Word)? */
#define elfround(x)     roundup((x), ELFROUNDSIZE)

Also, we have inconsistency with imgactl_elf.c/parse_notes(), which
uses 4-byte alignment:

		note = (const Elf_Note *)((const char *)(note + 1) +
		    roundup2(note->n_namesz, sizeof(Elf32_Addr)) +
		    roundup2(note->n_descsz, sizeof(Elf32_Addr)));

I suppose there were no issues before, because accidentally the sizes
of all notes we had were 8 bytes aligned.

Now, when I add new notes it will break things. I don't have strong
opinion, it will be ok for me to leave 8-byte alignment and fix
issues, just want to have strong support here :-)

BTW, looking at NetBSD code I see they set p_align in the note
segement to ELFROUNDSIZE:

        /* Write out the PT_NOTE header. */
        ws.psections->p_type = PT_NOTE;
        ws.psections->p_offset = notestart;
        ws.psections->p_vaddr = 0;
        ws.psections->p_paddr = 0;
        ws.psections->p_filesz = notesize;
        ws.psections->p_memsz = 0;
        ws.psections->p_flags = PF_R;
        ws.psections->p_align = ELFROUNDSIZE;

while we set to 0:

	/* The note segement. */
	phdr->p_type = PT_NOTE;
	phdr->p_offset = hdrsize;
	phdr->p_vaddr = 0;
	phdr->p_paddr = 0;
	phdr->p_filesz = notesz;
	phdr->p_memsz = 0;
	phdr->p_flags = 0;
	phdr->p_align = 0;

Shouldn't we set it to alignment size too? Note also, they set
"Segment is readable" flag.

> > 
> > 4) In libprocstat I added new functions and placed them under already
> > existent FBSD_1.3 version section in Symbol.map.
> > 
> > Shouldn't I bump the version? Won't I need any additional care if I
> > want to MFC the code to stable/9 and may be 8?
> Version of what ? MFC does not require any additional actions, FBSD_1.3
> is the valid version namespace in 9 and 8.

Ok. Now I see it was rather silly question :-). Thanks. For this and
your other notes.

-- 
Mikolaj Golub