Re: [1/2] 2.6.22-rc5: known regressions with patches

From: Ian McDonald
Date: Wed Jun 20 2007 - 19:02:57 EST


On 6/21/07, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
And yes, sometimes debugging *does* change what it debugs. In timing, if
nothing else, but also in the kinds of things you can do.

Totally agree.

For example, we
don't allow slab redzoning on data structures that have alignment
restrictions not compatible with the redzoning, and I'd argue that this is
more of the same: we just should not do DEBUG_RODATA if you expect to
change read-only data.


Well the description for DEBUG_RODATA is:
Mark the kernel read-only data as write-protected in the pagetables,
in order to catch accidental (and incorrect) writes to such const data.

What we are doing with kprobes is neither accidental, nor incorrect.

There's just no *point*.

Linus

I understand your philosophical viewpoint here. Anyway it's no biggie
as can keep the patch out of tree if I want it... Another option is to
be able to enable and disable protecting read only data via a sysctl
but that seems even uglier.

Anyway I'll stop wasting your time now.

Ian
--
Web: http://wand.net.nz/~iam4/
Blog: http://iansblog.jandi.co.nz
WAND Network Research Group
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