<br><font size=2><tt>Benjamin Herrenschmidt <benh@kernel.crashing.org>
wrote on 05/29/2007 09:24:15 AM:<br>
<br>
> Specifically, are everybody using the uc_regs pointer to get to the<br>
> mcontext or are some people likely to expect the mcontext to always
be<br>
> at the same offset from the beginning of the signal frame ?</tt></font>
<br>
<br><font size=2><tt>As far as I can see, both GDB and the GCC unwind-from-signal
code</tt></font>
<br><font size=2><tt>always read the uc_regs pointer. (Or the sigcontext.regs
pointer for</tt></font>
<br><font size=2><tt>old-style signal frames.)</tt></font>
<br><font size=2><tt><br>
> There are a few other issues... one is, the pad fields aren't cleared.<br>
> Thus how can userland or rt_sigreturn differenciate between a valid<br>
> highregs pointers and ramdom junk ? Is there a trick one of you can
come<br>
> up with that I could do to let userland/gdb/rt_sigreturn know that<br>
> there's something there ?</tt></font>
<br>
<br><font size=2><tt>One idea we had about this was to use a bit in uc_flags.
Those are</tt></font>
<br><font size=2><tt>completely unused today, but should always have been
initialized to 0.</tt></font>
<br><font size=2><tt><br>
</tt></font><font size=2 face="sans-serif"><br>
Mit freundlichen Gruessen / Best Regards<br>
<br>
Ulrich Weigand<br>
<br>
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