The following patch adds a new functionality to ptrace:
system call notification to the current process.

It applies to the 2.6.26 vanilla kernel for the x86 and s390 architectures.

It provides the following:
---------------------------------
   - Activation and de-activation of the functionality through ptrace
     system call
   - When the functionality is activated, the system call is not done
     and the calling process receives a SIGSYS signal.

What is it good for?
--------------------------
   - Debugging : a tracing tool can be implemented inside the space
     of the current thread and access the thread data directly from
     inside reducing task switch and IPC overhead.
   - Virtualization : a system call interposition mechanism can be
     implemneted inside the space of the current thread reducing the
     overhead of task switch and IPC and access directly all syscall
     parameters

What is missing?
----------------------
   - Port to other architectures.

It follows the patch itself.

-- 
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Pierre Morel
RTOS and Embedded Linux