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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
OK, fair enough. As the bug is really in my copy of glibc anyway, I'll
withdraw my patch.
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE