Messages in this thread | | | Date | Sun, 14 Aug 2005 07:50:22 -0700 | From | "Martin J. Bligh" <> | Subject | Re: [PATCH] Fix mmap_kmem (was: [question] What's the difference between /dev/kmem and /dev/mem) |
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--Arjan van de Ven <arjan@infradead.org> wrote (on Saturday, August 13, 2005 18:50:10 +0200):
> On Fri, 2005-08-12 at 09:35 -0700, Linus Torvalds wrote: >> >> On Thu, 11 Aug 2005, Steven Rostedt wrote: >> > >> > Found the problem. It is a bug with mmap_kmem. The order of checks is >> > wrong, so here's the patch. Attached is a little program that reads the >> > System map looking for the variable modprobe_path. If it finds it, then >> > it opens /dev/kmem for read only and mmaping it to read the contents of >> > modprobe_path. >> >> I'm actually more inclined to try to deprecate /dev/kmem.. I don't think >> anybody has ever really used it except for some rootkits. It only exists >> in the first place because it's historical. >> >> We do need to support /dev/mem for X, but even that might go away some >> day. >> >> So I'd be perfectly happy to fix this, but I'd be even happier if we made >> the whole kmem thing a config variable (maybe even default it to "off"). > > attached is a simple patch that does exactly this...
Whilst there's no normal legitimite usage for it, it is useful for debugging. One thing I often do is create a circular log buffer, then fish it back out by mmaping /dev/mem or /dev/kmem, and going by system.map offsets. No, nobody could claim it was clean or elegant, but it *is* useful. M.
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