Teaches systemd-stub how to load additional initrds from addon files.
This is very similar to the support for .ucode sections in addon files,
but with different ordering. Initrds from addons have a chance to
overwrite files from the base initrd in the UKI.
These variables closely mirror the existing
LoaderDevicePartUUID/LoaderImageIdentifier variables. But the Stub…
variables indicate the location of the stub/UKI (i.e. of systemd-stub),
while the Loader… variables indicate the location of the boot loader
(i.e. of systemd-boot). (Except of course, there is no boot loader used,
in which case both sets point to the stub/UKI, as a special case).
This actually matters, as we support that sd-boot runs off the ESP,
while a UKI then runs off XBOOTLDR, i.e. two distinct partitions.
This adds a ability to add alternative sections of a specific type in
the same UKI. The primary usecase is for supporting multiple different
kernel cmdlines that are baked into a UKI.
The mechanism is relatively simple (I think), in order to make it robust.
1. A new PE section ".profile" is introduced, that is a lot like
".osrel", but contains information about a specific "profile" to
boot. The ".profile" section can appear multiple times in the same
PE, and acts as delimiter indicating where a new profile starts.
Everything before the first ".profile" is called the "base profile",
and is shared among all other profiles, which can then override or
add addition PE sections on top.
2. An UKI's command line can be prefixed with an argument such as "@0" or
"@1" or "@2" which indicates the "profile" to boot. If no argument is
specified the default is profile 0. Also, a UKI that lacks any
.profile section is treated like one with only a profile 0, but with
no data in that profile section.
3. The stub will first search for its usual set of PE sections
(hereafter called "base sections"), and stop at the first .profile PE
section if any. It will then find the .profile matching the selected
profile by its index, and any sections found as part of that profile
on top of the base sections.
And that's already it.
Example: let's say a distro wants to provide a single UKI that can be
invoked in one of three ways:
1. The regular profile that just boots the system
2. A profile that boots into storagetm
3. A profile that initiates factory reset and reboots.
For this it would define a classic UKI with sections .linux, .initrd,
.cmdline, and whatever else it needs. The .cmdline section would contain
the kernel command line for the regular profile.
It would then insert one ".profile" section, with a contents like the
following:
ID=regular
This is the profile for profile 0. It would immediately afterwards add
another ".profile" section:
ID=storagetm
TITLE=Boot into Storage Target Mode
This would then followed with a .cmdline section that is just like the
basic one, but with "rd.systemd.unit=storage-target-mode.target"
suffixed. Then, another .profile section would be added:
ID=factory-reset
TITLE=Factory Reset
Which is then followed by one last PE section: a .cmdline one with
"systemd.unit=factory-reset.target" suffixed to te regular command line.
i.e. expressed in tabular form the above would be:
The base profile:
.linux
.initrd
.cmdline
.osrel
The regular boot profile:
.profile
The storagetm profile:
.profile
.cmdline
The factory reset profile:
.profile
.cmdline
You might wonder why the first .cmdline in the list above is placed in
the base profile rather than in the regular boot profile, given that it
is overriden in all other profiles anyway. And you are right. The only
reason I'd place it in the base profile is that it makes the UKI more
nicely extensible if later profiles are added that want to replace
something else instead of the .cmdline, for example .ucode or so. But it
really doesn't matter much.
While the primary usecase is of course multiple alternative command
lines, the concept is more powerful than that: for various usecases it
might be valuable to offer multiple choices of devicetree, ucode or
initrds.
The .profile contents is also passed to the invoked kernel as a file in
/.extra/profile (via a synthetic initrd). Thus, this functionality can
even be useful without overriding any section at all, simply by means of
reading that file from userspace.
Design choices:
1. On purposes I used a special command line marker (i.e. the "@" thing,
which maybe we should call the "profile selector"), that doesn't look
like a regular kernel command line option. This is because this is
really not a regular kernel command line option – we process it in
the stub, then remove it as prefix, and measure the unprefixed
command line only after that. The kernel will not see the profile
selector either. I think these special semantics are best
communicated by making it look substantially different from regular
options.
2. This moves around measurements a bit. Previously we measured our UKI
sections right after finding them. Now we first parse the profile
number from the command line, then search for the profile's sections,
and only then measure the sections we actually end up using for this
profile. I think that this logic makes most sense: measure what we
are using, not what we are overriding. Or in other words, if you boot
profile @3, then we'll measure .cmdline (assuming it exists) of
profile 3, and *not* measure .cmdline of the base profile. Also note
that if the user passes in a custom kernel command line via command
line arguments we'll strip off the profile selector (i.e. the initial
"@X" thing) before we pass it on.
3. The .profile stuff is supposed to be generic and extensible. For
example we could use it in future to mark "dangerous" options such as
factory reset, so that boot menus can ask for confirmation before
booting into it. Or we could introduce match expressions against
SMBIOS or other system identifiers, to filter out profiles on
specific hw.
Note btw, that PE allows defining multiple sections that point to the
same offsets in the file. This allows sharing payload under different
names. For example, if profile @4 and @7 shall carry the same .ucode
section, they can define .ucode in each profile and then make it point to
the same offset.
Also note that that one can even "mask" a base section in a profile, by
inserting an empty section. For example, if the base .dtb section should
not be used for profile @4, then add a section .dtb right after the
fourth .profile with a zero size to the UKI, and you will get your wish
fulfilled.
This code only contains changes to sd-stub. A follow-up commit will
teach sd-boot to also find this profile PE sections to synthesize
additional menu entries from a single UKI.
A later commit will add support for gnerating this via ukify.
Fixes: #24539
This is the most basic preparatory work for supporting multi-profile
UKIs.
(This temporarily drops an assert_cc() check which we'll address in the
next commit)
The original CVM detection logic for TDX assumes that the guest can see
the standard TDX CPUID leaf. This was true in Azure when this code was
originally written, however, current Azure now blocks that leaf in the
paravisor. Instead it is required to use the same Azure specific CPUID
leaf that is used for SEV-SNP detection, which reports the VM isolation
type.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
The construct is a POSIX invention, but it's just so useful, let's also
define it in EFI mode, so that we can use similar constructs in EFI mode
and userspace.
This commit adds support for loading, measuring and handling a ".ucode"
UKI section. This section is functionally an initrd, intended for
microcode updates. As such it will always be passed to the kernel first.
Adds a util function to sha256 an open fd (moved from dissect). Also
adds functions to check if a string contains a valid sha256 hash, and
parse it into a sha256 array.
ADD_SAFE/SUB_SAFE/MUL_SAFE do addition/subtraction/multiplication
respectively with an overflow check. If an overflow occurs these return
false, otherwise true. Example: (c = a + b) would become ADD_SAFE(&c, a,
b)
INC_SAFE/DEC_SAFE/MUL_ASSIGN_SAFE are like above but they also reassign
the first argument. Example: (a += b) would become INC_SAFE(&a, b)
This does what we do for system extension also for configuration
extension.
This is complicated by the fact that we previously looked for
<uki-binary>.d/*.raw for system extensions. We want to measure sysexts
and confexts to different PCRs (13 vs. 12) hence we must distinguish
them, but *.raw would match both kinds.
This commit solves this via the following mechanism: we'll load confexts
from *.confext.raw and sysexts from *.raw but will then enclude
*.confext.raw from the latter. This preserves compatibility but allows
us to somewhat reasonable distinguish both types of images.
The documentation is updated not going into this detail though, and
instead now claims that sysexts shall be *.sysext.raw and confexts
*.confext.raw even though we actually are more lenient than this. This
is simply to push people towards using the longer, more descriptive
suffixes.
I added an XML comment (<!-- … -->) about this to the docs, so that
whenever somebody notices the difference between code and docs
understands why and leaves it that way.
Ultimately we want to be able to recognize these in userspace, hence
make them available in both UEFI mode and userspace.
While we are at it, let's rename the fields a bit, reflecting more what
they measure, not what the metadata is that we store about them.
E.g. Consider the case ALIGN_TO(SIZE_MAX - 3, 4). The overflow check
passes as the condition
```
SIZE_MAX - 3 > SIZE_MAX - (4 - 1)
```
is false.
However, the value
```
l + ali - 1
```
may overflow as it is equivalent to
```
SIZE_MAX - 3 + 4 - 1
```
Currently we have a 100ms delay which allows for people to enter/show
the boot menu even when timeout is set to zero.
In a handful of cases, that may not be needed - both in terms of access
policy, as well as latency.
For example: the option to provide the boot menu may be hidden behind an
"expert only" UX in the OS, to avoid end users from accidentally
entering it.
In addition, the current 100ms input polling may cause unexpected
additional delays in the boot. Some example numbers from my SteamDeck:
- boot counting/rename/flush doubles 300us -> 600us
- seed/hash setup doubles 900us -> 1800us
- kernel/image load gets ~40% slower 107ms -> 167ms
It's not entirely clear why the UEFI calls gets slower, nevertheless the
information in itself proves useful.
This commit introduces a new option "menu-disabled", which omits the
100ms delay. The option is documented throughout the manual pages as
well as the Boot Loader Specification.
v2:
- use STR_IN_SET
v3:
- drop erroneous whitespace
v4:
- add a new LoaderFeature bit,
- don't change ABI keep TIMEOUT_* tokens the same
- move new token in the 64bit range, update API and storage for it
- change inc/dec behaviour to TIMEOUT_MIN : TIMEOUT_MENU_FORCE
- user cannot opt-in from sd-boot itself, add assert_not_reached()
v5:
- s/Menu disablement control/Menu can be disabled/
- rewrap comments to 109
- use SYNTHETIC_ERRNO(EOPNOTSUPP)
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
note that this slightly changes the semantic of assert when NDEBUG is
defined. if there's an extern function call (without attribute pure or
similar) then the compiler has to assume it has side effects and still
emit the function call.
whereas the old assert guaranteed that nothing will be evaluated on
NDEBUG.
Closes: https://github.com/systemd/systemd/issues/29408
This makes the special PE sections available again in our output EFI
images.
Since the compiler provides no way to mark a section as not allocated,
we use GNU assembler syntax to emit the sections instead. This ensures
the section data isn't emitted twice as load segments will only contain
allocating input sections.
The implementations are not 100% overlapping, so use different identifiers, so
that revocations can be done independently. e.g.: a bug that affects only
sd-boot won't necessarily cause old UKIs to be revoked.
The use of vcs_tag was dropped in #28567, which results in builds having
stale version information once new commit are made.
This also fixes a case where CI builds would have no version information
because they are checked out without any tags for git-describe to use.
Additionally, use `--git-dir` now, as that particular issues seems to
have been fixed by now.
I always found it confusing that most of our TPM related definitions are
in tpm2-util.h, but the PCR names in tpm-pcr.h, without the "2". Let's
fix that and make this systematic, in particular as the definitions in
the file all start with TPM2_ already.
No code flow changes, just some renaming.
We so far maintained two places for symboic names for PCRs. One in
tpm2-util.h and one in tpm-pcr.h.
Let's unify this into one, i.e. move the full list from tpm2-util.h into
tpm-pcr.h, replacing the short list placed so far there.
Systematically prefix the definitions with TPM2_ or tpm2_, to follow how
we do this for all other defines in this context.
No change in behaviour, just unification of tables.
We gained a bunch of new features that deserve reporting to userspace,
hence add matching flags for each.
This allows userspace to determine if installing addons in the ESP even
makes sense.
This is inspired by a similar changes in #28057
Yu Watanabe
anonymix007
Lennart Poettering
Tobias Fleig
Daniel P. Berrangé
Mike Yuan
Cristian Rodríguez
Adrian Vovk
Rose
Sam Leonard
Luca Boccassi
Emil Velikov
Zbigniew Jędrzejewski-Szmek
NRK
Jan Janssen