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Re: mips64 sigaction changes

On Fri, Mar 14, 2003 at 12:34:50PM -0300, Alexandre Oliva wrote:
> On Mar 14, 2003, Daniel Jacobowitz <drow at mvista dot com> wrote:
> > Well, I'd rather not.  If you follow linux-mips, Ralf has been talking
> > about removing sa_restorer while there are still no uses of it.
> My understanding is that he's not doing it for rt signals.  Or maybe
> he's just not dropping rt_sigreturn like it seemed like he planned to,
> and getting the kernel to set up the restorer in the stack (which is
> bad, since it involves flushing instruction caches or so).  Anyway,
> it's not like we're exporting sa_restorer, we're just using this
> feature like we must to ensure that, if the kernel does require
> sa_restorer, we do the right thing.  If it doesn't use sa_restorer,
> it's ok, we'll still work, and then we can drop this field at some
> point.

Er, OK, I think.  He was planning on moving the restorer off of the
stack and onto a static kernel page, when I spoke to him.  And
eliminating sa_restorer from the sigaction struct entirely.

> >> +/* NOTE: Please think twice before making any changes to the bits of
> >> +   code below.  GDB needs some intimate knowledge about it to
> >> +   recognize them as signal trampolines, and make backtraces through
> >> +   signal handlers work right.  Important are both the names
> >> +   (__restore_rt) and the exact instruction sequence.
> >> +   If you ever feel the need to make any changes, please notify the
> >> +   appropriate GDB maintainer.  */
> > This comment's also inappropriate.  GDB won't handle __restore or
> > __restore_rt at all.
> It should.  Otherwise, how can it get a stack trace from within a
> signal handler?

By recognizing the code, not by recognizing the names.  Only the i386
GDB port does this to my knowledge.

Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

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