Re: [PATCH][CFT] [coredump] don't use __kernel_write() on kmap_local_page()

Ira Weiny
2022-10-03T19:31:49Z

On Mon, Oct 03, 2022 at 07:48:28PM +0900, J. R. Okajima wrote:
> Ira Weiny:
> > On Wed, Sep 28, 2022 at 07:29:43PM +0100, Al Viro wrote:
> > > On Tue, Sep 27, 2022 at 11:51:17PM +0100, Al Viro wrote:
> > > > [I'm going to send a pull request tomorrow if nobody yells;
> > > > please review and test - it seems to work fine here, but extra
> > > > eyes and extra testing would be very welcome]
>
> I tried gdb backtrace 'bt' command with the new core by v6.0, and it
> doesn't show the call trace correctly. Is it related to this commit?
>

Are you also getting something like this?

BFD: warning: /mnt/9p/test-okajima/core is truncated: expected core file size >= 225280, found: 76616

I did not see that before. I'm running through this patch vs a fix to
kmap_to_page()[1] and I may have gotten the 2 crossed up. So I'm retesting
with your test below.

Ira

[1] https://lore.kernel.org/linux-mm/20221003040427.1082050-1-ira.weiny@intel.com/

> test program
> ----------------------------------------
> void f(int n)
> {
> printf("%d\n", n);
> if (!n)
> kill(getpid(), SIGQUIT);
> f(--n);
> }
>
> int main(int argc, char *argv[])
> {
> f(atoi(argv[1]));
> return 0;
> }
> ----------------------------------------
> ulimit -c unlimited
> coredump 2
> gdb coredump core
> bt
> ----------------------------------------
> expected result
> kill
> f
> f
> f
> main
> ----------------------------------------
> actual result
> ??
> ??
> ----------------------------------------
>
>
> J. R. Okajima