mkosi: Changes to allow booting with sanitizers in mkosi

- Extra memory because ASAN needs it
- The environment variables to make the sanitizers more useful
- LD_PRELOAD because the ASAN DSO needs to be the first in the list
- The sanitizer library packages
- Disable syscall filters because they interfere with ASAN
- Disable systemd-hwdb-update because it's super slow when systemd-hwdb
  is built with sanitizers
- Take the value for meson's b_sanitize option from the SANITIZERS
  environment variable

docs/HACKING.md

@@ -140,6 +140,11 @@ enabled that are suitable when hacking on systemd (such as internal
 documentation consistency checks). Those are not useful when compiling for
 distribution and can be disabled by setting `-Dmode=release`.
 
+## Sanitizers in mkosi
+
+See [Testing systemd using sanitizers](TESTING_WITH_SANITIZERS.md) for more information
+on how to build with sanitizers enabled in mkosi.
+
 ## Fuzzers
 
 systemd includes fuzzers in `src/fuzz/` that use libFuzzer and are automatically

docs/TESTING_WITH_SANITIZERS.md

@@ -13,6 +13,22 @@ This is mostly done automagically by various CI systems for each PR, but you may
 want to do it locally as well. The process slightly varies depending on the
 compiler you want to use and which part of the test suite you want to run.
 
+## mkosi
+
+To build with sanitizers in mkosi, create a file 20-local.conf in mkosi.default.d/ and add the following
+contents:
+
+```
+[Content]
+Environment=SANITIZERS=address,undefined
+```
+
+The value of `SANITIZERS` is passed directly to meson's `b_sanitize` option, See
+https://mesonbuild.com/Builtin-options.html#base-options for the format expected by the option. Currently,
+only the sanitizers supported by gcc can be used, which are `address` and `undefined`.
+
+Note that this will only work with a recent version of mkosi (>= 14 or by running mkosi directly from source).
+
 ## gcc
 gcc compiles in sanitizer libraries dynamically by default, so you need to get
 the shared libraries first - on Fedora these are shipped as a separate packages

mkosi.build

@@ -5,6 +5,9 @@ set -e
 # This is a build script for OS image generation using mkosi (https://github.com/systemd/mkosi).
 # Simply invoke "mkosi" in the project directory to build an OS image.
 
+ASAN_OPTIONS=strict_string_checks=1:detect_stack_use_after_return=1:check_initialization_order=1:strict_init_order=1:disable_coredump=0:use_madv_dontdump=1
+UBSAN_OPTIONS=print_stacktrace=1:print_summary=1:halt_on_error=1
+
 # On Fedora "ld" is (unfortunately — if you ask me) managed via
 # "alternatives". Since we'd like to support building images in environments
 # with only /usr/ around (e.g. mkosi's UsrOnly=1 option), we have the problem
@@ -61,7 +64,8 @@ if [ ! -f "$BUILDDIR"/build.ninja ] ; then
                 -D man=false \
                 -D translations=false \
                 -D version-tag="${VERSION_TAG}" \
-                -D mode=developer
+                -D mode=developer \
+                -D b_sanitize="${SANITIZERS:-none}"
 fi
 
 cd "$BUILDDIR"
@@ -71,7 +75,15 @@ if [ "$WITH_TESTS" = 1 ] ; then
                 getent group $id >/dev/null || groupadd -g $id testgroup$id
         done
 
-        ninja test
+        if [ -n "$SANITIZERS" ]; then
+                export ASAN_OPTIONS="$ASAN_OPTIONS"
+                export UBSAN_OPTIONS="$UBSAN_OPTIONS"
+                TIMEOUT_MULTIPLIER=3
+        else
+                TIMEOUT_MULTIPLIER=1
+        fi
+
+        meson test --timeout-multiplier=$TIMEOUT_MULTIPLIER
 fi
 cd "$SRCDIR"
 
@@ -120,3 +132,42 @@ if [ -n "$CI_BUILD" ]; then
         cp -v "$SRCDIR/test/mkosi-check-and-shutdown.sh" "$DESTDIR/usr/lib/systemd/mkosi-check-and-shutdown.sh"
         chmod +x "$DESTDIR/usr/lib/systemd/mkosi-check-and-shutdown.sh"
 fi
+
+if [ -n "$SANITIZERS" ]; then
+        LD_PRELOAD=$(ldd $BUILDDIR/systemd | grep libasan.so | awk '{print $3}')
+
+        mkdir -p "$DESTDIR/etc/systemd/system.conf.d"
+
+        cat > "$DESTDIR/etc/systemd/system.conf.d/10-asan.conf" <<EOF
+[Manager]
+ManagerEnvironment=ASAN_OPTIONS=$ASAN_OPTIONS\\
+                   UBSAN_OPTIONS=$UBSAN_OPTIONS\\
+                   LD_PRELOAD=$LD_PRELOAD
+DefaultEnvironment=ASAN_OPTIONS=$ASAN_OPTIONS\\
+                   UBSAN_OPTIONS=$UBSAN_OPTIONS\\
+                   LD_PRELOAD=$LD_PRELOAD
+EOF
+
+        # ASAN logs to stderr by default. However, journald's stderr is connected to /dev/null, so we lose
+        # all the ASAN logs. To rectify that, let's connect journald's stdout to the console so that any
+        # sanitizer failures appear directly on the user's console.
+        mkdir -p "$DESTDIR/etc/systemd/system/systemd-journald.service.d"
+
+        cat > "$DESTDIR/etc/systemd/system/systemd-journald.service.d/10-stdout-tty.conf" <<EOF
+[Service]
+StandardOutput=tty
+EOF
+
+        # Both systemd and util-linux's login call vhangup() on /dev/console which disconnects all users.
+        # This means systemd-journald can't log to /dev/console even if we configure `StandardOutput=tty`. As
+        # a workaround, we modify console-getty.service to disable systemd's vhangup() and disallow login
+        # from calling vhangup() so that journald's ASAN logs correctly end up in the console.
+
+        mkdir -p "$DESTDIR/etc/systemd/system/console-getty.service.d"
+
+        cat > "$DESTDIR/etc/systemd/system/console-getty.service.d/10-no-vhangup.conf" <<EOF
+[Service]
+TTYVHangup=no
+CapabilityBoundingSet=~CAP_SYS_TTY_CONFIG
+EOF
+fi

mkosi.default.d/10-systemd.conf

@@ -6,6 +6,8 @@
 Format=gpt_btrfs
 Bootable=yes
 HostonlyInitrd=yes
+# Prevent ASAN warnings when building the image
+Environment=ASAN_OPTIONS=verify_asan_link_order=false
 
 [Packages]
 BuildDirectory=mkosi.builddir
@@ -16,6 +18,7 @@ SourceFileTransferFinal=copy-git-others
 [Host]
 QemuHeadless=yes
 NetworkVeth=yes
+QemuMem=2G
 
 [Validation]
 Password=

mkosi.default.d/centos_epel/10-mkosi.centos_epel

@@ -78,6 +78,8 @@ Packages=
         e2fsprogs
         # xxd is provided by the vim-common package
         vim-common
+        libasan
+        libubsan
         # Required to run systemd-networkd-tests.py
         python3
         iproute

mkosi.default.d/debian/10-mkosi.debian

@@ -74,6 +74,8 @@ Packages=
         nano
         strace
         xxd
+        # Provides libasan/libubsan
+        gcc
         # Required to run systemd-networkd-tests.py
         python3
         iproute2

mkosi.default.d/fedora/10-mkosi.fedora

@@ -77,6 +77,9 @@ Packages=
         compsize
         # xxd is provided by the vim-common package
         vim-common
+        # Sanitizers
+        libasan
+        libubsan
         # Required to run systemd-networkd-tests.py
         python
         iproute

mkosi.default.d/opensuse/10-mkosi.opensuse

@@ -75,3 +75,5 @@ Packages=
         util-linux
         # xxd is provided by the vim package
         vim
+        # Provides libasan/libubsan
+        gcc

mkosi.default.d/ubuntu/10-mkosi.ubuntu

@@ -72,6 +72,8 @@ Packages=
         nano
         strace
         xxd
+        # Provides libasan/libubsan
+        gcc
         # Required to run systemd-networkd-tests.py
         python3
         iproute2

mkosi.postinst

@@ -1,8 +1,18 @@
 #!/bin/sh
 # SPDX-License-Identifier: LGPL-2.1-or-later
 
-if [ "$1" = "final" ] && command -v bootctl > /dev/null && [ -d "/efi" ]; then
-    bootctl install
+if [ "$1" = "final" ]; then
+    if command -v bootctl > /dev/null && [ -d "/efi" ]; then
+        bootctl install
+    fi
+
+    if [ -n "$SANITIZERS" ]; then
+        # ASAN and syscall filters aren't compatible with each other.
+        find / -name '*.service' -type f -exec sed -i 's/^\(MemoryDeny\|SystemCall\)/# \1/' {} +
+
+        # `systemd-hwdb update` takes > 50s when built with sanitizers so let's not run it by default.
+        systemctl mask systemd-hwdb-update.service
+    fi
 fi
 
 # Temporary workaround until https://github.com/openSUSE/suse-module-tools/commit/158643414ddb8d8208016a5f03a4484d58944d7a