Messages in this thread | | | Date | Thu, 01 Mar 2007 21:35:20 +0900 | From | "Kawai, Hidehiro" <> | Subject | Re: [PATCH 0/4] coredump: core dump masking support v3 |
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Hi,
Markus Gutschke wrote:
> Kawai, Hidehiro wrote: > >> This patch series is version 3 of the core dump masking feature, >> which provides a per-process flag not to dump anonymous shared >> memory segments. > > I just wanted to remind you that you need to be careful about dumping > the [vdso] segment no matter whether you omit other segments. I didn't > actually try running your patches, and if the kernel doesn't actually > consider this segment anonymous and shared, things might already work > fine as is.
Thank you for your advice and sorry for not replying soon.
Fortunately, the latest kernel uses VM_ALWAYSDUMP flag to always dump the vdso segment. My patchset doesn't change this behavior. So we don't need to worry about the vdso segment.
> As an alternative to your kernel patch, you could achieve the same goal > in user space, by linking my coredumper > http://code.google.com/p/google-coredumper/ into your binaries and > setting up appropriate signal handlers. An equivalent patch for > selectively omitting memory regions would be trivial to add.
As far as I can see, google-coredumper has more flexibility. Can google-coredumper satisfy the following requirements easily?
Requirements are: (1) a user can change the core dump settings _anytime_ - sometimes want to dump anonymous shared memory segments and sometimes don't want to dump them (2) a user can change the core dump settings of _any processes_ (although permission checks are performed) - in a huge application which forks many processes, a user hopes that some processes dump anonymous shared memory segments and some processes don't dump them
And reliability of the core dump feature is also important.
> While this > does give you more flexibility, it of course has the drawback of > requiring you to change your applications, so there still is some > benefit in a kernelspace solution.
And all the software vendors don't necessarily apply google-coredumper. If the vendor doesn't apply it, the user will be bothered by huge core dumps or the buggy application which remains unfixed. So I believe that in kernel solution is still needed.
Thanks, -- Hidehiro Kawai Hitachi, Ltd., Systems Development Laboratory
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