[Bug external/31520] New: [gdb/external] Handle kernel.yama.ptrace_scope != 0

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

https://sourceware.org/bugzilla/show_bug.cgi?id=31520

            Bug ID: 31520
           Summary: [gdb/external] Handle kernel.yama.ptrace_scope != 0
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: external
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

openSUSE Tumbleweed recently changed the default of the
kernel.yama.ptrace_scope setting from 0 to 1.

This causes attach-type test-cases to fail.

For me, it's easily fixable by manually overriding the default in say
/etc/sysctl.conf or /etc/sysctl.d/10-ptrace.conf.

But there may be users who either don't want to do this, or are not allowed to
do this on the system at hand.

Using sudo should still work, but that may also be considered unacceptable, or
an inconvenience because the user really wants to be debugging as user $USER,
not as root.

I found this link (  https://wiki.archlinux.org/title/Capabilities ) which
advertises a way to still run as user, while having increased priviliges:
...
$ sudo -E capsh --caps="cap_setpcap,cap_setuid,cap_setgid+ep
cap_sys_ptrace+eip" --keep=1 --user="$USER" --addamb="cap_sys_ptrace"
--shell=/usr/bin/gdb -- -p <pid>
...

This does not yet work for me on openSUSE Leap 15.4, I need to debug this
further.

But it occurred to me that:
- this setting and problem is unmentioned in our docs, and
- that a script that supports allowing ptrace capabilities that would work on
  any linux system (or indicate why not) would be useful.

Whether this script should be part of the gdb contrib scripts (there are other
tools than gdb who would need the same script), and delivered to users or not,
I'm not sure.  But it would be good to have it somewhere, and to be able to
point to its location in the docs.

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