Previously there was a weird asymmetry: initially we'd resolve the
specified prefix path when chasing symlinks together with the actual
path we were supposed to cover, except when we hit an absolute symlink
where we'd use the root as it was. Let's unify handling here: the prefix
path is never resolved, and always left as it is.
This in particular fixes issues with symlinks in the prefix path, as
that confused the check that made sure we never left the root directory.
Fixes: #14634
Replaces: #14635
```
ninja -C build
ninja: Entering directory `build'
[29/101] Generating systemd_boot.so with a custom command.
FAILED: src/boot/efi/systemd_boot.so
/usr/bin/ld -o src/boot/efi/systemd_boot.so -T /usr/lib64/gnuefi/elf_x64_efi.lds -shared -Bsymbolic -nostdlib -znocombreloc -L /usr/lib64 /usr/lib64/gnuefi/crt0-efi-x64.o src/boot/efi/disk.c.o src/boot/efi/graphics.c.o src/boot/efi/measure.c.o src/boot/efi/pe.c.o src/boot/efi/util.c.o src/boot/efi/boot.c.o src/boot/efi/console.c.o src/boot/efi/crc32.c.o src/boot/efi/random-seed.c.o src/boot/efi/sha256.c.o src/boot/efi/shim.c.o -lefi -lgnuefi /usr/lib/gcc/x86_64-redhat-linux/10/libgcc.a
/usr/bin/ld: src/boot/efi/graphics.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: multiple definition of `loader_guid'; src/boot/efi/disk.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: first defined here
/usr/bin/ld: src/boot/efi/pe.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: multiple definition of `loader_guid'; src/boot/efi/disk.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: first defined here
/usr/bin/ld: src/boot/efi/util.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: multiple definition of `loader_guid'; src/boot/efi/disk.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: first defined here
/usr/bin/ld: src/boot/efi/boot.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: multiple definition of `loader_guid'; src/boot/efi/disk.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: first defined here
/usr/bin/ld: src/boot/efi/console.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: multiple definition of `loader_guid'; src/boot/efi/disk.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: first defined here
/usr/bin/ld: src/boot/efi/random-seed.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: multiple definition of `loader_guid'; src/boot/efi/disk.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: first defined here
/usr/bin/ld: src/boot/efi/shim.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: multiple definition of `loader_guid'; src/boot/efi/disk.c.o:/home/sus/tt/systemd/build/../src/boot/efi/util.h:58: first defined here
[31/101] Generating stub.c.o with a custom command.
ninja: build stopped: subcommand failed.
make: *** [Makefile:2: all] Error 1
```
Let's lock this down a bit. Effectively nothing much changes, since the
default PK policy will allow users on the VT to change VT. Only users
with no local VT session won't be able to switch VTs.
This way we shuld be able to order mounts properly against their backing
services in case complex storage is used (i.e. LUKS), even if the device
path used for mounting the devices is different from the expected device
node of the backing service.
Specifically, if we have a LUKS device /dev/mapper/foo that is mounted
by this name all is trivial as the relationship can be established a
priori easily. But if it is mounted via a /dev/disk/by-uuid/ symlink or
similar we only can relate the device node generated to the one mounted
at the moment the device is actually established. That's because the
UUID of the fs is stored inside the encrypted volume and thus not
knowable until the volume is set up. This patch tries to improve on this
situation: a implicit After=blockdev@.target dependency is generated for
all mounts, based on the data from /proc/self/mountinfo, which should be
the actual device node, with all symlinks resolved. This means that as
soon as the mount is established the ordering via blockdev@.target will
work, and that means during shutdown it is honoured, which is what we
are looking for.
Note that specifying /etc/fstab entries via UUID= for LUKS devices still
sucks and shouldn't be done, because it means we cannot know which LUKS
device to activate to make an fs appear, and that means unless the
volume is set up at boot anyway we can't really handle things
automatically when putting together transactions that need the mount.
This catches up with 9d06297e26 and adapts
the change made to swap units. We generally don't want to react
a-posteriori to swap devices disappearing, bad things will happen
anyway.
Lennart Poettering
Franck Bui
Zbigniew Jędrzejewski-Szmek
sangelovic
Yu Watanabe
Susant Sahani
Kevin Kuehler
Anita Zhang