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[Bug tapsets/14325] for arm/s390x, the nd_syscall tapsets need improvement


http://sourceware.org/bugzilla/show_bug.cgi?id=14325

--- Comment #1 from David Smith <dsmith at redhat dot com> 2012-07-05 13:57:41 UTC ---
(In reply to comment #0)
> Possible solutions include:
> 
> - Have the *_arg() functions return a dummy value when asked for an argument it
> can't handle.
> 
> - Have each architecture provide a function, something like syscall_max_args(),
> that would provide the maximum argument that this architecture supports.  This
> function could be tested in each probe alias, like this:
> 
>   argstr = sprintf("%d %d %d %d %d", int_arg(1), int_arg(2), int_arg(3),
>            int_arg(4), (syscall_max_args() >= 5 ? int_arg(5) : -1))
> 
> - Continue like commit 65ddca0 and just do architecture checks everywhere
> needed.

Another solution would be to define variants of the *_arg() funtions that take
a default value (to be used when the argument isn't available).  It could look
something like this (where '0' is the default value for arg 4 and -1 is the
default value for arg 5):

  argstr = sprintf("%d %d %d %d %d", int_arg(1), int_arg(2), int_arg(3),
           int_arg_default(4, 0), int_arg(5, -1))

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