This adds sch_act_target/schActTarget accessor names for the
switch_thread/SwitchToThread constructor of the scheduler_action
datatype at the aspec and Haskell level, respectively
Signed-off-by: Michael McInerney <michael.mcinerney@proofcraft.systems>
This includes replacing previous ASpec names for such constants with
the names used in Haskell/ExecSpec to avoid duplication. This also
makes some of the proofs slightly more generic.
Signed-off-by: Gerwin Klein <gerwin.klein@proofcraft.systems>
Introduce Kernel_Config theory for storage of non-architecture-specific
seL4 configuration variables that are shared by the abstract and design
specs.
Remove `num_domains`, in lieu of `numDomains` that is now defined only
in `Kernel_Config.thy`. The definition is hidden and must be referred to
as Kernel_Config.numDomains_def when avoiding unfolding is not possible.
Include required properties of `numDomains` as lemmas.
Signed-off-by: Rafal Kolanski <rafal.kolanski@proofcraft.systems>
Session-qualified imports will be required for Isabelle2018 and help clarify
the structure of sessions in the build tree.
This commit mainly adds a new set of sessions for lib/, including a Lib
session that includes most theories in lib/ and a few separate sessions for
parts that have dependencies beyond CParser or are separate AFP sessions.
The group "lib" collects all lib/ sessions.
As a consequence, other theories should use lib/ theories by session name,
not by path, which in turns means spec and proof sessions should also refer
to each other by session name, not path, to avoid duplicate theory errors in
theory merges later.
Colloquially known as "invert-fastpath".
Update verification efforts on ARM for the following seL4 changes:
- scheduling decisions done in possibleSwitchTo are moved to the
scheduler
- possibleSwitchTo only checks whether the candidate is valid for a
fast switch, not its priority, accepting possible candidates
immmediately as a switch-to scheduler action
- the scheduler checks the candidate against the current thread and
against the bitmaps before making a decision
- attemptSwitchTo and switchIfRequiredTo are gone
- scheduler is now more complicated, and numerous proofs related to it
are rewritten from scratch
- fast path now checks ready queues via the scheduler bitmaps
- L2 scheduler bitmap order reversed for better cache locality
Many iterations between the kernel and verification teams were needed
to get this right.
This reverts:
- a67b443ca5
"SELFOUR-242: update goal number based indentation in Fastpath_C"
- f704cf0404
"SELFOUR-242: invert bitfield scheduler and optimise fast path"
Verification confirmed functional correctness and refinement of the
system in this case. However, guarantees on thread scheduling and
fairness are not modeled in the current verification. Once this issue is
addressed, SELFOUR-242 will be re-examined.
* Reverse the level 2 of the bitmap scheduler to move the highest priority
threads' level 2 entries into the same cache line as the level 1.
* Use the bitfield scheduler to make the fast path a more common occurrence.
* Change possibleSwitchTo to not invoke scheduler when the fast path would not
invoke it either (using implicit assumptions about the current thread being
the highest priority schedulable thread)
These changes to the automatons are required by:
SELFOUR-242: invert bitfield scheduler and optimise fast path
Details:
When we enter the kernel, the domain time left (ksDomainTime) is never zero.
If we entered on a timer interrupt, we may decrement it to zero before the
scheduler runs. If we do so, we set the scheduler state to choose_new_thread.
When choosing a new thread, the scheduler switches to a new domain if the
present one is required, and sets the new domain time left from domain_list
(ksDomSchedule).
When entering the kernel on a non-interrupt event, we never touch the domain
time left, which trivially preserves the new constraints.
To prove these, we had to ban a transition from kernel entry to kernel being
preempted when handling an interrupt event in InfoFlow. This is fine, as by
design handling interrupts is not meant to be preempted by interrupts.
To finish the proof of refinement to C, the specification for checkPrio
needed strengthening: the checkPrio spec now takes a machine word
argument. In the spec, priorities are still stored as 8-bit quantities,
however. Once the spec was strenthened, it was possible to remove some
redundant checks and mask operations from the C code.
A thread's maximum controlled priority (MCP) determines the maximum
thread priority or MCP it can assign to another thread (or itself).
Gerwin Klein
Michael McInerney
Rafal Kolanski
Gerwin Klein
Matthew Brecknell
Rafal Kolanski
Alejandro Gomez-Londono
Joel Beeren
Sophie Taylor
Gerwin Klein
Gao Xin
Daniel Matichuk