binutils-gdb/gdb/aarch32-tdep.h
Thiago Jung Bauermann bbb12eb9c8 gdb/arm: Remove tpidruro register from non-FreeBSD target descriptions
Commit 92d48a1e4e ("Add an arm-tls feature which includes the tpidruro
register from CP15.") introduced the org.gnu.gdb.arm.tls feature, which
adds the tpidruro register, and unconditionally enabled it in
aarch32_create_target_description.

In Linux, the tpidruro register isn't available via ptrace in the 32-bit
kernel but it is available for an aarch32 program running under an arm64
kernel via the ptrace compat interface.  This isn't currently implemented
however, which causes GDB on arm-linux with 64-bit kernel to list the
register but show it as unavailable, as reported by Tom de Vries:

  $ gdb -q -batch a.out -ex start -ex 'p $tpidruro'
  Temporary breakpoint 1 at 0x512

  Temporary breakpoint 1, 0xaaaaa512 in main ()
  $1 = <unavailable>

Simon Marchi then clarified:

> The only time we should be seeing some "unavailable" registers or memory
> is in the context of tracepoints, for things that are not collected.
> Seeing an unavailable register here is a sign that something is not
> right.

Therefore, disable the TLS feature in aarch32 target descriptions for Linux
and NetBSD targets (the latter also doesn't seem to support accessing
tpidruro either, based on a quick look at arm-netbsd-nat.c).

This patch fixes the following tests:

Running gdb.base/inline-frame-cycle-unwind.exp ...
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 3: backtrace when the unwind is broken at frame 3
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 5: backtrace when the unwind is broken at frame 5
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 1: backtrace when the unwind is broken at frame 1

Tested with Ubuntu 22.04.3 on armv8l-linux-gnueabihf in native,
native-gdbserver and native-extended-gdbserver targets with no regressions.

PR tdep/31418
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31418

Approved-By: John Baldwin <jhb@FreeBSD.org>
2024-02-29 12:27:27 -03:00

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/* Copyright (C) 2019-2024 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef AARCH32_TDEP_H
#define AARCH32_TDEP_H
struct target_desc;
/* Get the AArch32 target description. */
const target_desc *aarch32_read_description (bool tls);
#endif /* aarch32-tdep.h. */