On Tue, 26 Feb 2019, Mark Wielaard wrote: > On Tue, 2019-02-26 at 09:33 +0100, Richard Biener wrote: > > On Mon, 25 Feb 2019, Mark Wielaard wrote: > > > Since the introduction of GNU Property notes this is (sadly) no > > > longer > > > the correct way to iterate through ELF notes. The padding of names > > > and > > > desc might now depend on the alignment of the PT_NOTE segment. > > > https://sourceware.org/ml/binutils/2018-09/msg00359.html > > > > Ick, that's of course worse ;) So it's not entirely clear what > > the correct thing to do is - from how I read the mail at the above > > link only iff sh_align of the note section is exactly 8 the above > > ALIGN would use 8 byte alignment and else 4 is correct (independent > > on sh_align). Or can I assume sh_align of the note section is > > "correct" for all existing binaries? Note also the eventual > > difference > > between note sections and note program headers which have another, > > possibly different(?) alignment? It's of course "easy" to replace > > 4 above by info->dlpi_phdr[i].p_align (but the align field differs > > in width between elfclass 32 and 64 ... :/). > > > > So - is merely changing the re-alignment from 4 to > > info->dlpi_phdr[i].p_align "correct"? > > Yes, you will have multiple note segments one that combines the 4 > padded notes and one that combines the 8 padded notes. > Some tools put 0 or 1 in the align field, so you might want to use > (completely untested): > align = (p_align <= 4) ? 4 : 8; > offset += ALIGN ((ALIGN (sizeof (uint32_t) * 3 + namesz, align) > + descsz), align);
That would mean when p_align == 8 the note name isn't 8-aligned but just 4-aligned? That is, sizeof (Elf*_Nhdr) == 12, and the name starts right after that instead of being aligned according to p_align? That sounds odd... So p_align only applies to the descriptor? Richard. > Cheers, > > Mark > > -- Richard Biener <rguent...@suse.de> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)
