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SubjectRe: [PATCH] Kprobes: Add kprobes smoke tests that run on boot
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On Tue, 2008-01-08 at 22:00 +0100, Andi Kleen wrote:
> Ananth N Mavinakayanahalli <ananth@in.ibm.com> writes:
> > kernel/kprobes.c | 2
> > kernel/test_kprobes.c | 216 ++++++++++++++++++++++++++++++++++++++++++++++++
>
> Can you put this somewhere else please? I know there are already some
> test files in kernel/* but imho they all belong into some other directory.
>
> + if (!err)
> + init_test_probes();
> return err;
>
> Couldn't this be just a normal initcall? Perhaps even a module_init(),
> then it would be possible to use as a module too.
>
> -Andi

I have no problem with that, but if we want to make it buildable as a
module, the call to get_kprobe() needs to be replaced with some other
gcc-inline-defeating mechanism, or we need to export get_probe(). I
much prefer the former, since get_kprobe() is a kprobes-internal
function.

Anybody know an architecture-independent way (other than noinline, which
doesn't always work) of making gcc decide not to inline a function?
E.g., does taking (and using) the function's address do it?

Jim Keniston

>From Ananth's patch:
+static noinline u32 kprobe_target(u32 value)
+{
+ /*
+ * gcc ignores noinline on some architectures unless we stuff
+ * sufficient lard into the function. The get_kprobe() here is
+ * just for that.
+ *
+ * NOTE: We aren't concerned about the correctness of
get_kprobe()
+ * here; hence, this call is neither under !preempt nor with the
+ * kprobe_mutex held. This is fine(tm)
+ */
+ if (get_kprobe((void *)0xdeadbeef))
+ printk(KERN_INFO "Kprobe smoke test: probe on
0xdeadbeef!\n");
+
+ return (value / div_factor);
+}



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