On Mon, Sep 26, 2022 at 05:15:54PM +0200, наб wrote:
> Hi!
>
> On Mon, Sep 26, 2022 at 10:16:02AM +0200, Geert Uytterhoeven wrote:
> > Thanks for your patch, which is now commit 53c2bd679017277f
> > ("a.out: remove define-only CMAGIC, previously magic number") in
> > driver-core/driver-core-next.
> >
> > On Fri, Sep 16, 2022 at 12:40 AM наб <nabijaczleweli@xxxxxxxxxxxxxxxxxx> wrote:
> > > The last user was removed in 5.1 in
> > > commit 08300f4402ab ("a.out: remove core dumping support")
> > > but this is part of the UAPI headers, so this may want to either wait
> > > until a.out is removed entirely, or be removed from the magic number doc
> > > and silently remain in the header
> >
> > Indeed. This is part of uapi, and might break some unknown
> > userspace, while the gain is limited. Do we really want to reduce
> > include/uapi/linux/a.out.h piecewise (e.g. N_BADMAG() seems to be
> > unused, too), instead of keeping it until a.out support is removed
> > completely?
>
> Not really, but it looked like a magic number in the magic-number.rst
> sense due to the field being "magic" and the unintuitive type naming:
> I hadn't realised it's part of the on-disk format
> re-examination shows that it very well may be (have been).
>
> > Anyway, even at that point, it might be wise to keep the header file
> > around, as people have expressed the desire to run a.out binaries
> > through a userspace-compatibility wrapper.
>
> Agreed. Scissor-patch that reverts the removal below.
>
> > > A cursory glance on DCS didn't show any user code actually using this
> > > value
> >
> > What is DCS?
>
> Debian Code Search; in this case my query was:
> https://codesearch.debian.net/search?q=%5CbCMAGIC%5Cb&literal=0
>
> There's a few false positives here but all results that are using CMAGIC
> to mean this CMAGIC (and aren't hurd code copied from linux)
> just re-define it.
>
> > > Documentation/process/magic-number.rst | 1 -
> > > Documentation/translations/it_IT/process/magic-number.rst | 1 -
> > > Documentation/translations/zh_CN/process/magic-number.rst | 1 -
> > > Documentation/translations/zh_TW/process/magic-number.rst | 1 -
> > > include/uapi/linux/a.out.h | 3 ---
> > > 5 files changed, 7 deletions(-)
> > >
> > > diff --git a/include/uapi/linux/a.out.h b/include/uapi/linux/a.out.h
> > > index 5fafde3798e5..bb15da96df2a 100644
> > > --- a/include/uapi/linux/a.out.h
> > > +++ b/include/uapi/linux/a.out.h
> > > @@ -70,9 +70,6 @@ enum machine_type {
> > > The first page is unmapped to help trap NULL pointer references */
> > > #define QMAGIC 0314
> > >
> > > -/* Code indicating core file. */
> > > -#define CMAGIC 0421
> > > -
> > > #if !defined (N_BADMAG)
> > > #define N_BADMAG(x) (N_MAGIC(x) != OMAGIC \
> > > && N_MAGIC(x) != NMAGIC \
> >
> > Gr{oetje,eeting}s,
> > Geert
>
> Best,
> наб
>
> -- >8 --
> Subject: [PATCH] a.out: restore CMAGIC
>
> Part of UAPI and the on-disk format:
> this means that it's not a magic number per magic-number.rst,
> and it's best to leave it untouched to avoid breaking userspace
> and suffer the same fate as a.out in general
>
> Fixes: commit 53c2bd679017 ("a.out: remove define-only CMAGIC,
> previously magic number")
> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@xxxxxxxxxxxxxxxxxx>
> ---
> include/uapi/linux/a.out.h | 3 +++
> 1 file changed, 3 insertions(+)
Thanks, I'll take this through my tree as it has the offending commit in
it.
greg k-h
