*GDB* can again dump memory protected by the "VM_DONTDUMP" flag
Previous changes to the GNU Debugger *GDB* made the behavior of the "gcore" command more similar to the behavior of the Linux kernel when dumping process memory to increase data security. Consequently, users of *GDB* could not dump memory protected by the "VM_DONTDUMP" flag. The new "set dump-excluded-mappings" setting has been added to *GDB* to enable dumping of memory with this flag. As a result, users can dump the whole process memory with *GDB* again.
Versions prior to gdb-7.6.1-83.el7, unconditionally included all memory regions when generating a dump file. Starting with this version, by default GDB will both inspect /proc/PID/coredump_filter, and unconditionally ignore memory regions marked with VM_DONTDUMP.
While it's possible requesting to GDB to ignore /proc/PID/coredump_filter by using the 'set use-coredump-filter' command, there's no way to request it to ignore the VM_DONTDUMP flag.
The change that altered the behavior is this one:
commit 38e1562bc360e0b89490b9b6903e1982a2f2f7fe
Author: Jan Kratochvil <jan.kratochvil>
Date: Fri Nov 27 20:43:41 2015 +0100
Support for /proc/PID/coredump_filter (Sergio Durigan Junior, RH
BZ 1265351).
Sergio Durigan Junior, RH BZ 1265351
7.6.1-83.el7
- Resolves: rhbz#1265351
I've posted a tentative fix for this upstream:
- https://sourceware.org/ml/gdb-patches/2017-11/msg00724.html
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2018:0701
Versions prior to gdb-7.6.1-83.el7, unconditionally included all memory regions when generating a dump file. Starting with this version, by default GDB will both inspect /proc/PID/coredump_filter, and unconditionally ignore memory regions marked with VM_DONTDUMP. While it's possible requesting to GDB to ignore /proc/PID/coredump_filter by using the 'set use-coredump-filter' command, there's no way to request it to ignore the VM_DONTDUMP flag. The change that altered the behavior is this one: commit 38e1562bc360e0b89490b9b6903e1982a2f2f7fe Author: Jan Kratochvil <jan.kratochvil> Date: Fri Nov 27 20:43:41 2015 +0100 Support for /proc/PID/coredump_filter (Sergio Durigan Junior, RH BZ 1265351). Sergio Durigan Junior, RH BZ 1265351 7.6.1-83.el7 - Resolves: rhbz#1265351 I've posted a tentative fix for this upstream: - https://sourceware.org/ml/gdb-patches/2017-11/msg00724.html