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Re: [rfc] Handle broken CFI for signal trampolines in libc on amd64-linux
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: mark dot kettenis at xs4all dot nl (Mark Kettenis)
- Cc: gdb-patches at sourceware dot org
- Date: Sat, 22 Nov 2008 16:30:36 +0100 (CET)
- Subject: Re: [rfc] Handle broken CFI for signal trampolines in libc on amd64-linux
Mark Kettenis wrote:
> > On Fri, Nov 21, 2008 at 02:33:29AM +0100, Ulrich Weigand wrote:
> > > Anyway, while it is certainly good that this is fixed, I'm still
> > > wondering why we should rely on that when we have a hard-coded
> > > sigtramp detector that should be working just fine under any
> > > circumstances.
> >
> > I think that one reason was the extra work of the signal handler
> > sniffer. The amd64 one doesn't do much for named functions, though,
> > and functions with CFI are likely to be named. I suggest asking
> > Mark Kettenis's opinion.
>
> My memory is a bit hazy on this, but I think the idea was that the signal
> frame unwinder would only be used for older versions of linux/glibc that
> don't provide the necessary CFI, and that newer versions would provide
> correct CFI which would give the kernel/glibc people complete freedom on
> how to implement signal frames. As such, I'm inclined to say "no" to your
> diff.
OK, fair enough. As the bug is really in my copy of glibc anyway, I'll
withdraw my patch.
Bye,
Ulrich
--
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE
Ulrich.Weigand@de.ibm.com