[Bug ports/16169] New: AArch64 clone.S is missing some CFI markup

["tromey at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=16169

            Bug ID: 16169
           Summary: AArch64 clone.S is missing some CFI markup
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ports
          Assignee: unassigned at sourceware dot org
          Reporter: tromey at redhat dot com
                CC: carlos at redhat dot com, roland at gnu dot org

Created attachment 7277
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7277&action=edit
untested patch

While debugging bug #16155 I noticed that the AArch64
clone.S does not properly note that the stack ends.
Other arches (I checked ARM and x86-64) do this with
CFI directives.

I'm attaching a completely untested (not even compiled)
patch that shows what I think ought to be done.  The
key bit is marking the link register as unavailable.


Also, I noticed that the AArch64 clone.S does not
implement this part of AAPCS64:

"The end of the frame record chain is indicated by the address zero in the
address for the previous frame."

This is in Section 5.2.3 The Frame Pointer.

At least based on my reading of the x86-64 clone.S, the
code run in the new clone ought to ensure this; but I am
not completely certain.

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