Messages in this thread | | | From | Roland McGrath <> | Subject | Re: [PATCH] x86: fix typo(?) in step.c | Date | Wed, 5 Mar 2008 23:52:23 -0800 (PST) |
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> Roland - i guess this means block-stepping (a new ptrace feature in .25) > is not particularly well-tested. Do you have any standalone testcases > that could be run?
I'm pretty sure that noone really uses it yet. The test I used when I originally wrote the feature is in the ptrace-tests suite. (See http://sourceware.org/systemtap/wiki/utrace/tests about that suite.) I haven't particularly tested it since then, if it got broken later.
http://sources.redhat.com/cgi-bin/cvsweb.cgi/tests/ptrace-tests/tests/block-step.c?cvsroot=systemtap
Be sure to compile with current kernel-headers, or hand-tweak to define PTRACE_SINGLEBLOCK. Use -std=gnu99 -D_GNU_SOURCE.
The bogon came in commit eee3af4a2c83a97fff107ddc445d9df6fded9ce4, the introduction of the ptrace BTS stuff. Sorry I did not scour and cite every problem in that patch, since I had NAK'd the entire thing as needing more careful review and incremental introduction after 2.6.25.
As I said then, one of my concerns was with the low-level tweaks not yet sufficiently baked, independent from my reservations about the ptrace feature. Your #if'ing out of the user ABI additions for 2.6.25 does nothing to remove the unknown new risks from all the tweaks with fingers in the low-level arch stuff. This is the sort of thing I was concerned about. (And this one is easy.)
The block-step test only tested that PTRACE_SINGLEBLOCK worked right. I just souped it up to also test that PTRACE_SINGLESTEP still works immediately afterwards. This still does not show any problem from this bug. The case that would be broken by it is rather more arcane. I haven't worked out the test case that fails with the bogon.
Thanks, Roland
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