Messages in this thread | | | Date | Fri, 10 Nov 2006 13:00:09 +0900 | From | "Magnus Damm" <> | Subject | Re: [PATCH 02/02] Elf: Align elf notes properly |
| |
On 11/10/06, Horms <horms@verge.net.au> wrote: > On Thu, Nov 09, 2006 at 07:00:22AM -0700, Eric W. Biederman wrote: > > Magnus Damm <magnus@valinux.co.jp> writes: > > > > > elf: Align elf notes properly > > > > > > The kernel currently contains several elf note aligment implementations. Most > > > implementations follow the spec on 32-bit platforms, but none current aligns > > > the notes correctly on 64-bit platforms. This patch tries to fix this by > > > interpreting the 64-bit and 32-bit elf specs as the following: > > > > > > offset bytes name > > > 0 4 n_namesz -+ -+ > > > 4 4 n_descsz | elf note header | > > > 8 4 n_type -+ | elf note entry size - N4 > > > 12 N1 name | > > > N2 N3 desc -+ > > > > > > WS = word size in bytes (4 for 32 bit, 8 for 64 bit) > > > N1 = roundup(n_namesz + sizeof(elf note header), WS) - sizeof(elf note header) > > > N2 = sizeof(elf note header) + N1 > > > N3 = roundup(n_descsz, WS) > > > N4 = sizeof(elf note header) + N1 + N2 > > > > > > The elf note header contains three 32-bit values on 32-bit and 64-bit systems. > > > The header is followed by name and desc data together with padding. The > > > alignment and padding varies depending on the word size. > > > > I see your point and I disagree. The notes in a kernel generated > > core dump do not vary in size. Find me some implementation evidence that > > anyone ever added the extra 4 bytes of alignment to the description and the > > padding fields and I will be ready to consider this. Currently this > > just appears to be reading a draft spec that doesn't match reality. > > Or perhaps a spec that hasn't been implemented correctly. > I guess that the real question is, what padding is correct?
I see no point in aligning to 32-bit boundaries on 64-bit platforms. Their intention was most likely to align to the word size IMO, so this is most likely a "thinko" left over from whoever ported the code from 32-bit to 64-bit.
How we chose to align on 64-bit platforms is another issue, either we fix it soon or live with the fact that we are not following the 64-bit draft spec. Either way is fine with me.
/ magnus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |