packages: add the Debugging packages section

src/SUMMARY.md

@@ -24,6 +24,7 @@
   - [Limitations of packages](packages/limitations.md)
   - [Missing packages](packages/missing.md)
   - [Upgrading packages](packages/upgrading.md)
+  - [Debugging packages](packages/debugging.md)
   - [Useful commands](packages/commands.md)
 - [Compiling "Hello World"](helloworld/README.md)
 - [Benchmarking guidance](benchmarking/README.md)

src/packages/debugging.md

@@ -0,0 +1,68 @@
+# Debugging packages
+
+Similarly to the FreeBSD Project, CheriBSD packages are built with CheriBSD
+ports that are based on FreeBSD ports.
+By default, the packages are built with optimisation levels defined in CheriBSD
+ports or upstream third-party software projects.
+Unfortunately, the FreeBSD ports build system does not allow to build ports with
+optimisations and debug symbols at the same time.
+As a consequence of that, you might discover that debug symbols are missing when
+debugging a program with the GDB debugger.
+
+In order to allow users to use optimised and debug CheriABI packages, CheriBSD
+provides two package repositories with them: the default repository with
+optimisations and without debug symbols called `CheriBSD`, and the debug
+repository without optimisations and with debug symbols called `CheriBSD-debug`.
+Note that we do not provide debug packages for the hybrid and benchmark ABIs.
+
+You can enable the debug repository by first creating a directory for custom
+package repository configuration files:
+```
+mkdir -p /usr/local/etc/pkg/repos
+```
+and then creating a configuration file that enables `CheriBSD-debug`:
+```
+echo "CheriBSD-debug: { enabled: yes }" >/usr/local/etc/pkg/repos/CheriBSD-debug.conf
+```
+
+You can reinstall all previously installed default packages to replace them with
+debug packages:
+
+```
+pkg64c upgrade -fr CheriBSD-debug
+```
+
+Alternatively, you can selectively reinstall a package:
+
+```
+pkg64c upgrade -r CheriBSD-debug <pkg-name>
+```
+
+However, keep in mind that in such case only the package you list is
+reinstalled, leaving its dependencies intact.
+
+Once you enable the `CheriBSD-debug` repository, the `CheriBSD` repository is
+used by default.
+You have to use the `-r` flag to switch to `CheriBSD-debug` in a `pkg64c`
+command, e.g.:
+
+```
+pkg64c install -r CheriBSD-debug <pkg-name>
+```
+
+If you want to use only the `CheriBSD-debug` repository, you can create a
+configuration file that disables the `CheriBSD` repository:
+
+```
+echo "CheriBSD: { enabled: no }" > /usr/local/etc/pkg/repos/CheriBSD.conf
+```
+
+You can also check if an installed package was fetched from the default or debug
+package repository:
+
+```
+pkg64c query '%n %R' <pkg-name>
+```
+
+You can omit `<pkg-name>` in the above command to list all packages with their
+repositories.