Tracing only write page-faults

Adam Lackorzynski adam at
Sun Apr 8 21:03:29 CEST 2012


On Thu Apr 05, 2012 at 16:32:22 +0400, Ivan Bludov wrote:
> I want to trace all write page-faults from an application. I use the
> pager that wait for page-fault and maps the fpage to thread calling
> l4_ipc_send_and_wait setting L4_ITEM_MAP. For tracing only write
> page-faults I map fpage as L4_FPAGE_RO if it was read-pf and then I
> map the same fpage with L4_FPAGE_RW if the next write-pf occurs. (I
> mean I map the same fpage with the different flags twice). But an
> application doesn't continue run. Also I have tried to
> l4_task_unmap(L4_FP_OTHER_SPACES) this fpage before mapping it as
> L4_FPAGE_RW. It doesn't work. What should I use to change fpage's
> rights to L4_FPAGE_RW for fpage that is already mapped as L4_FPAGE_RO
> for an application?

The approach you're doing looks perfectly ok. Mapping with more rights
should just work as you describe it. The source of the mapping is
available as rw I suppose?

Adam                 adam at

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