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SubjectRe: [RFC] [PATCH 0/2] Futex fault injection

* Sripathi Kodi <sripathik@in.ibm.com> wrote:

> Hi,
>
> This patch set adds fault injection for futex subsystem. It adds
> faults at places where reading/writing from user space can return
> EFAULT. This will be useful in testing any significant change to futex
> subsystem.

Instead of this unacceptably ugly and special-purpose debugfs interface,
please extend perf events to allow event injection. Some other places in
the kernel (which deal with rare events) want/need this capability too.

A good way to do it would be to define tracepoints in these places via a
new kind of TRACE_EVENT(), which would also define an event_injected_*()
callback to use.

So, for example, instead of:

if (futex_should_fail(&fail_futex_efault, 1))
return -EFAULT;

if (unlikely(!access_ok(rw, uaddr, sizeof(u32)))) {
trace_get_futex_key_efault(uaddr);
return -EFAULT;
}

We'd have something like:

if (unlikely(!access_ok(rw, uaddr, sizeof(u32))) ||
event_injected_get_futex_key_efault()) {

trace_get_futex_key_efault(uaddr);
return -EFAULT;
}

And each separate event injection point could thus be triggered
individually.

To use this there would be a separate facility to inject events - via
the perf events ioctl for example.

Ingo


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