[Bug tdep/31418] [gdb/tdep, arm] $tpidruro unavailable

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

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

--- Comment #3 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Thiago Bauermann
<bauermann@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=bbb12eb9c84aa2b32480b7c022c494c2469ef717

commit bbb12eb9c84aa2b32480b7c022c494c2469ef717
Author: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Date:   Mon Feb 26 19:11:45 2024 -0300

    gdb/arm: Remove tpidruro register from non-FreeBSD target descriptions

    Commit 92d48a1e4eac ("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>

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