On Wed, Jul 18, 2012 at 03:04:39PM -0700, Andrew Morton wrote:
> On Tue, 17 Jul 2012 13:36:55 -0400
> Vivek Goyal <vgo...@redhat.com> wrote:
>
> > Last line of vmcoreinfo note does not end with \n. Parsing all the lines
> > in note becomes easier if all lines end with \n instead of trying to special
> > case the last line.
> >
> > I know atleast one tool, vmcore-dmesg in kexec-tools tree which made the
> > assumption that all lines end with \n. I think it is a good idea to
> > fix it.
> >
> > Signed-off-by: Vivek Goyal <vgo...@redhat.com>
> > ---
> > kernel/kexec.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Index: linux-2.6/kernel/kexec.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/kexec.c 2012-07-17 19:26:38.844033784 -0400
> > +++ linux-2.6/kernel/kexec.c 2012-07-17 23:51:33.311701781 -0400
> > @@ -1424,7 +1424,7 @@ static void update_vmcoreinfo_note(void)
> >
> > void crash_save_vmcoreinfo(void)
> > {
> > - vmcoreinfo_append_str("CRASHTIME=%ld", get_seconds());
> > + vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
> > update_vmcoreinfo_note();
> > }
>
> huh, that was a screwup. And now we have to make what must be
> viewed as a non-back-compatible ABI change.
>
> Ho hum, presumably there isn't a lot of code out there which is
> dependent upon a non-newline-terminated CRASHTIME record.
I think so. AFAIK, makedumpfile (vmcore filtering utility) is only
user of CRASHTIME=.
>
> Why did this work at all, anyway? Is CRASHTIME always the last-emitted
> record?
Yes, CRASHTIME= is always the last emitted line in vmcoreinfo note.
I had a quick look at makedumpfile code and looks like they read the whole
note, dump it to a file and then do fgets() on the file in a loop. As it is
last line in the file, fgets encounters EOF and reads the CRASHTIME= line
successfully. So even after this change makedumpfile should remain
unaffected.
CCing makedumpfile maintainer, Atsushi Kumagai.
Thanks
Vivek
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