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From: "ahmedsayeed1982 at yahoo dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug tdep/27015] ARC: "eret" value is collected from the wrong data
 in register cache
Date: Sun, 27 Jun 2021 17:52:24 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D27015

Ahmed Sayeed <ahmedsayeed1982 at yahoo dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ahmedsayeed1982 at yahoo d=
ot com

--- Comment #2 from Ahmed Sayeed <ahmedsayeed1982 at yahoo dot com> ---
--------------8<--------------
  if (regnum =3D=3D gdbarch_pc_regnum (gdbarch))
    regnum =3D ARC_ERET_REGNUM;
  regcache->raw_collect (regnum, buf + arc_linux_core_reg_offsets[regnum]);
-------------->8--------------

Root cause:
Although this is using the correct offset (ERET register's), it is also
changing the REGNUM itself.  Therefore, raw_collect (regnum, ...) is
not reading from "pc" anymore.

Consequence:
This bug affects the "native ARC gdb" badly and causes kernel code to jump
to addresses after the breakpoint and not executing the "breakpoint"ed
instructions at all.  That "native ARC gdb" feature is not upstream yet and
is in review at the time of writing [1].  http://michielleunens.tech/

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