Re: [PATCH -v4 9/9] tracing: add function graph tracer support for MIPS

[David Daney <ddaney@caviumnetworks.com>]

Steven Rostedt wrote:
[...]
> We're not doing back traces. We need to modify the return of the
> function being called. Note, the above functions that end with ";" are
> leaf functions. Non leaf functions show "{" and end with "}".
> 
> The trick here is to find a reliable way to modify the return address.
> 

Well that's what I get for chiming in without fully understanding the 
context.

I think it is fine to search backwards from the ($ra - 8) of the call to 
_mcount until you encounter the adjustment of $sp.  If you encounter a 
store of $ra, you can assume that the function will use the stored value 
when returning, otherwise modify the value restored to $ra (passed in 
$at).  That is probably what you were doing to begin with.

David Daney