Provide ways of crashing the kernel through debugfs
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From: Simon Kagstrom on 29 Jan 2010 01:20 On Thu, 28 Jan 2010 16:38:02 +0200 Artem Bityutskiy <dedekind1(a)gmail.com> wrote: > On Wed, 2010-01-27 at 10:53 +0800, Américo Wang wrote: > > > Well, it provides a few more ways of crashing the kernel. That's > > > basically the only additional feature you'll get. > > > > Yeah, I can see that, but why do I need to care how I crash the kernel > > as long as I can crash it in a way. > > But Simon did explain in his first e-mail why he cares. You or others > might care for similar reasons. Another argument for the patch is that it's simple and well-contained, it doesn't touch any other code apart from the driver itself. It is also easy to extend with other tests, e.g., provoking kernel hangs to test watchdogs and so on. // Simon -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Andrew Morton on 29 Jan 2010 05:40 On Fri, 29 Jan 2010 07:13:24 +0100 Simon Kagstrom <simon.kagstrom(a)netinsight.net> wrote: > On Thu, 28 Jan 2010 16:38:02 +0200 > Artem Bityutskiy <dedekind1(a)gmail.com> wrote: > > > On Wed, 2010-01-27 at 10:53 +0800, Am__rico Wang wrote: > > > > Well, it provides a few more ways of crashing the kernel. That's > > > > basically the only additional feature you'll get. > > > > > > Yeah, I can see that, but why do I need to care how I crash the kernel > > > as long as I can crash it in a way. > > > > But Simon did explain in his first e-mail why he cares. You or others > > might care for similar reasons. > > Another argument for the patch is that it's simple and well-contained, > it doesn't touch any other code apart from the driver itself. > > It is also easy to extend with other tests, e.g., provoking kernel > hangs to test watchdogs and so on. > Yes, it's the sort of thing which lots of people have written throw-away ad-hoc versions of. It probably makes sense to do it once, do it right to save people from having to rererereinvent that wheel. What do others think? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Eric W. Biederman on 1 Feb 2010 23:20 Andrew Morton <akpm(a)linux-foundation.org> writes: > On Fri, 29 Jan 2010 07:13:24 +0100 Simon Kagstrom <simon.kagstrom(a)netinsight.net> wrote: > >> On Thu, 28 Jan 2010 16:38:02 +0200 >> Artem Bityutskiy <dedekind1(a)gmail.com> wrote: >> >> > On Wed, 2010-01-27 at 10:53 +0800, Am__rico Wang wrote: >> > > > Well, it provides a few more ways of crashing the kernel. That's >> > > > basically the only additional feature you'll get. >> > > >> > > Yeah, I can see that, but why do I need to care how I crash the kernel >> > > as long as I can crash it in a way. >> > >> > But Simon did explain in his first e-mail why he cares. You or others >> > might care for similar reasons. >> >> Another argument for the patch is that it's simple and well-contained, >> it doesn't touch any other code apart from the driver itself. >> >> It is also easy to extend with other tests, e.g., provoking kernel >> hangs to test watchdogs and so on. >> > > Yes, it's the sort of thing which lots of people have written > throw-away ad-hoc versions of. It probably makes sense to do it once, > do it right to save people from having to rererereinvent that wheel. > > What do others think? I think it makes sense, and in fact we have already merged one attempt at doing this generically. drivers/misc/lkdtm.c I think Simon's patch adds some additional interesting failure modes. write_after_free, corrupt_stack_write, unaligned_load_store. Simon is there any chance you can change your patch to an enhancement of lkdtm? lkdtm actually digs into the interesting failure points with a jprobe to trigger the harder to reproduce scenarios. Like stack overflow in an interrupt handler. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Simon Kagstrom on 2 Feb 2010 03:20
On Mon, 01 Feb 2010 20:16:46 -0800 ebiederm(a)xmission.com (Eric W. Biederman) wrote: > Andrew Morton <akpm(a)linux-foundation.org> writes: > > Yes, it's the sort of thing which lots of people have written > > throw-away ad-hoc versions of. It probably makes sense to do it once, > > do it right to save people from having to rererereinvent that wheel. > > > > What do others think? > > I think it makes sense, and in fact we have already merged one attempt > at doing this generically. drivers/misc/lkdtm.c So this functionality was already there - it would appear that I didn't do my research good enough then (I did actually look for this kind of thing). If something, I guess it shows that the kernel source is getting big! To add to the irony, I work for a company that works on "DTM", although it's not related to this functionality :-) > I think Simon's patch adds some additional interesting failure modes. > write_after_free, corrupt_stack_write, unaligned_load_store. > > Simon is there any chance you can change your patch to an enhancement of lkdtm? > > lkdtm actually digs into the interesting failure points with a jprobe > to trigger the harder to reproduce scenarios. Like stack overflow in > an interrupt handler. Yes, this would be a better way of supporting the crash functionality. I'll take a look on integrating the extra tests into lkdtm. I think it would also be good to provide a debugfs interface to lkdtm similar to what provoke-crash has. Right now you have to set it up via module parameters, and for some tests (write_after_free) I think that's a limitation since it often doesn't crash immediately. // Simon -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |