[Bug server/30453] New: gdbserver cannot set breakpoints when /proc/pid/mem is not writable

["manojgupta at google dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30453

            Bug ID: 30453
           Summary: gdbserver cannot set breakpoints when  /proc/pid/mem
                    is not writable
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: server
          Assignee: unassigned at sourceware dot org
          Reporter: manojgupta at google dot com
  Target Milestone: ---

In ChromeOS, we upgraded recently to gdb 13.1. Users are now reporting that
remote debugging using gdbserver now does not work as breakpoints can not be
set.

the error looks like:

# gdb
GNU gdb (Chromium OS 13.1 vanilla) 13.1
(gdb) target remote :1234
Remote debugging using :1234

0x0000007ff7fda920 in _start () from target:/lib/ld-linux-aarch64.so.1
(gdb) b main
Breakpoint 1 at 0x5555550770: file hello.c, line 4.
(gdb) n
Single stepping until exit from function _dl_start,
which has no line number information.
Warning:
Cannot insert breakpoint 1.
Cannot access memory at address 0x5555550770

Command aborted.

The debugging used to work in gdb 11.2 and 12.1.
I bisected  the problem to the following commit:
commit 421490af33bfbfe8a8429f0e43fb3e9f8727476e
Author: Pedro Alves <pedro@palves.net>
Date:   Mon Mar 28 18:35:34 2022 +0100

    gdbserver/linux: Access memory even if threads are running


Looks like it needs a fix up when /proc/pid/mem is not writable similar to
local debugging  patch:

commit dd09fe0d53242a5f6a86d2822b0cfdeb3f5baa8f
Author: Keith Seitz <keiths@redhat.com>
Date:   Tue Jul 26 19:11:04 2022 +0100

    gdb/linux_nat: Write memory using ptrace if /proc/pid/mem is not writable

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