Session_requester inherits from Dynamic_rom_session::Content_producer
which specifies the Buffer_capacity_exceeded exception which is thrown
on insufficient buffer space.
In the timeout framework, we maintain a translation factor value to
translate between time and timestamps. To raise precision we scale-up
the factor when we calculate it and scale-down the result of its
appliance later again. This up and down scaling is achieved through
left and right shifting. Until now, the shift width was statically
choosen. However, some platforms need a big shift width and others a
smaller one. The one static shift width couldn't cover all platforms
which caused overflows or precision problems.
Now, the shift width is choosen optimally for the actual translation
factor each time it gets re-calculated. This way, we can take care that
the shift always renders the best precision level without the risk for
overflows.
Ref #2400
Apparently this construct leads to a compiler errors like
error: second operand to the conditional operator is of type ‘void’, but
the third operand is neither a throw-expression nor of type ‘void’
With the capability-quota mechanism, the terminal-session won't always
be constructed completely on the first try (we may run out of caps in
the middle of the construction). Therefore, all members of the object
must be properly destructable. Furthermore, the patch replaces the
sliced heap by a heap to avoid allocating a new dataspace for each line
of the cell array.
Previously, the Genode::Timer::curr_time always used the
Timer_session::elapsed_ms RPC as back end. Now, Genode::Timer reads
this remote time only in a periodic fashion independently from the calls
to Genode::Timer::curr_time. If now one calls Genode::Timer::curr_time,
the function takes the last read remote time value and adapts it using
the timestamp difference since the remote-time read. The conversion
factor from timestamps to time is estimated on every remote-time read
using the last read remote-time value and the timestamp difference since
the last remote time read.
This commit also re-works the timeout test. The test now has two stages.
In the first stage, it tests fast polling of the
Genode::Timer::curr_time. This stage checks the error between locally
interpolated and timer-driver time as well as wether the locally
interpolated time is monotone and sufficiently homogeneous. In the
second stage several periodic and one-shot timeouts are scheduled at
once. This stage checks if the timeouts trigger sufficiently precise.
This commit adds the new Kernel::time syscall to base-hw. The syscall is
solely used by the Genode::Timer on base-hw as substitute for the
timestamp. This is because on ARM, the timestamp function uses the ARM
performance counter that stops counting when the WFI (wait for
interrupt) instruction is active. This instruction, however is used by
the base-hw idle contexts that get active when no user thread needs to
be scheduled. Thus, the ARM performance counter is not a good choice for
time interpolation and we use the kernel internal time instead.
With this commit, the timeout library becomes a basic library. That means
that it is linked against the LDSO which then provides it to the program it
serves. Furthermore, you can't use the timeout library anymore without the
LDSO because through the kernel-dependent LDSO make-files we can achieve a
kernel-dependent timeout implementation.
This commit introduces a structured Duration type that shall successively
replace the use of Microseconds, Milliseconds, and integer types for duration
values.
Open issues:
* The timeout test fails on Raspberry PI because of precision errors in the
first stage. However, this does not render the framework unusable in general
on the RPI but merely is an issue when speaking of microseconds precision.
* If we run on ARM with another Kernel than HW the timestamp speed may
continuously vary from almost 0 up to CPU speed. The Timer, however,
only uses interpolation if the timestamp speed remained stable (12.5%
tolerance) for at least 3 observation periods. Currently, one period is
100ms, so its 300ms. As long as this is not the case,
Timer_session::elapsed_ms is called instead.
Anyway, it might happen that the CPU load was stable for some time so
interpolation becomes active and now the timestamp speed drops. In the
worst case, we would now have 100ms of slowed down time. The bad thing
about it would be, that this also affects the timeout of the period.
Thus, it might "freeze" the local time for more than 100ms.
On the other hand, if the timestamp speed suddenly raises after some
stable time, interpolated time can get too fast. This would shorten the
period but nonetheless may result in drifting away into the far future.
Now we would have the problem that we can't deliver the real time
anymore until it has caught up because the output of Timer::curr_time
shall be monotone. So, effectively local time might "freeze" again for
more than 100ms.
It would be a solution to not use the Trace::timestamp on ARM w/o HW but
a function whose return value causes the Timer to never use
interpolation because of its stability policy.
Fixes#2400
This patch reduces the number of exception types by facilitating
globally defined exceptions for common usage patterns shared by most
services. In particular, RPC functions that demand a session-resource
upgrade not longer reflect this condition via a session-specific
exception but via the 'Out_of_ram' or 'Out_of_caps' types.
Furthermore, the 'Parent::Service_denied', 'Parent::Unavailable',
'Root::Invalid_args', 'Root::Unavailable', 'Service::Invalid_args',
'Service::Unavailable', and 'Local_service::Factory::Denied' types have
been replaced by the single 'Service_denied' exception type defined in
'session/session.h'.
This consolidation eases the error handling (there are fewer exceptions
to handle), alleviates the need to convert exceptions along the
session-creation call chain, and avoids possible aliasing problems
(catching the wrong type with the same name but living in a different
scope).
This patch mirrors the accounting and trading scheme that Genode employs
for physical memory to the accounting of capability allocations.
Capability quotas must now be explicitly assigned to subsystems by
specifying a 'caps=<amount>' attribute to init's start nodes.
Analogously to RAM quotas, cap quotas can be traded between clients and
servers as part of the session protocol. The capability budget of each
component is maintained by the component's corresponding PD session at
core.
At the current stage, the accounting is applied to RPC capabilities,
signal-context capabilities, and dataspace capabilities. Capabilities
that are dynamically allocated via core's CPU and TRACE service are not
yet covered. Also, the capabilities allocated by resource multiplexers
outside of core (like nitpicker) must be accounted by the respective
servers, which is not covered yet.
If a component runs out of capabilities, core's PD service prints a
warning to the log. To observe the consumption of capabilities per
component in detail, the PD service is equipped with a diagnostic
mode, which can be enabled via the 'diag' attribute in the target
node of init's routing rules. E.g., the following route enables the
diagnostic mode for the PD session of the "timer" component:
<default-route>
<service name="PD" unscoped_label="timer">
<parent diag="yes"/>
</service>
...
</default-route>
For subsystems based on a sub-init instance, init can be configured
to report the capability-quota information of its subsystems by
adding the attribute 'child_caps="yes"' to init's '<report>'
config node. Init's own capability quota can be reported by adding
the attribute 'init_caps="yes"'.
Fixes#2398
This patch reworks the implementation of core's RAM service to make use
of the 'Session_object' and to remove the distinction between the
"metadata" quota and the managed RAM quota. With the new implementation,
the session implicitly allocates its metadata from its own account. So
there is not need to handle 'Out_of_metadata' and 'Quota_exceeded' via
different exceptions. Instead, the new version solely uses the
'Out_of_ram' exception.
Furthermore, the 'Allocator::Out_of_memory' exception has become an alias
for 'Out_of_ram', which simplifies the error handling.
Issue #2398
This patch makes use of the new 'Quota_transfer::Account' by the service
types in base/service.h and uses 'Quota_transfer' objects in
base/child.cc and init/server.cc.
Furthermore, it decouples the notion of an 'Async_service' from
'Child_service'. Init's 'Routed_service' is no longer a 'Child_service'
but is based on the new 'Async_service' instead.
With this patch in place, quota transfers do no longer implicitly use
'Ram_session_client' objects. So transfers can in principle originate
from component-local 'Ram_session_component' objects, e.g., as used by
noux. Therefore, this patch removes a strumbling block for turning noux
into a single threaded component in the future.
Issue #2398
This patch replaces the 'Parent::Quota_exceeded',
'Service::Quota_exceeded', and 'Root::Quota_exceeded' exceptions
by the single 'Insufficient_ram_quota' exception type.
Furthermore, the 'Parent' interface distinguished now between
'Out_of_ram' (the child's RAM is exhausted) from
'Insufficient_ram_quota' (the child's RAM donation does not suffice to
establish the session).
This eliminates ambiguities and removes the need to convert exception
types along the path of the session creation.
Issue #2398
This patch replaces the former use of size_t with the use of the
'Ram_quota' type to improve type safety (in particular to avoid
accidentally mixing up RAM quotas with cap quotas).
Issue #2398
The 'Ram_allocator' interface contains the subset of the RAM session
interface that is needed to satisfy the needs of the 'Heap' and
'Sliced_heap'. Its small size makes it ideal for intercepting memory
allocations as done by the new 'Constrained_ram_allocator' wrapper
class, which is meant to replace the existing 'base/allocator_guard.h'
and 'os/ram_session_guard.h'.
Issue #2398
This commit moves the headers residing in `repos/base/include/spec/*/drivers`
to `repos/base/include/drivers/defs` or repos/base/include/drivers/uart`
respectively. The first one contains definitions about board-specific MMIO
iand RAM addresses, or IRQ lines. While the latter contains device driver
code for UART devices. Those definitions are used by driver implementations
in `repos/base-hw`, `repos/os`, and `repos/dde-linux`, which now need to
include them more explicitely.
This work is a step in the direction of reducing 'SPEC' identifiers overall.
Ref #2403
Since init no longer provides public headers, we have to adjust the
existing users of this headers. The 'init/child_config.h' is used only
by GDB monitor. So the patch moves the header there as an interim fix.
The 'init/child_policy.h' is still used by a few components, so we have
to keep a trimmed-down version of it for now.
This patch enables init to apply changes of any server's <provides>
declarations in a differential way. Servers can in principle be extended
by new services without re-starting them. Of course, changes of the
<provides> declarations may affect clients or would-be clients as this
information is taken into account for the session routing.
The optional 'version' attribute allows for the forced restart of a
child with an otherwise unmodified start node. The specified value is
also reflected in the state report.
This patch covers the resolution of the ROM route for child binaries
via the generic label-rewriting mechanics. Now, the <binary> node has
become merely sytactic sugar for a route like the following:
<start name="test"/>
<route>
<service name="ROM" unscoped_label="test">
<parent label="test-binary-name"/> </service>
...
</route>
...
</start>
A change of the binary name has an effect on the child's ROM route to
the binary and thereby implicitly triggers a child restart due to the
existing re-validation of the routing.
With this check in place, one can safely construct an 'Xml_generator'
even if the report is disabled. This relieves the user of the reporter
from the need to distinguish enabled from disabled reports.
This patch improves the accuracy of init's quota-saturation feature
(handing out all slack quota to a child by specifying an overly high RAM
quota for the child) and makes the RAM preserved by init configurable.
The preservation is specified as follows:
! <config>
! ...
! <resource name="RAM" preserve="1M"/>
! ...
! </config>
If not specified, init has a reasonable default of 160K (on 32 bit) and
320K (on 64 bit).
This patch lets init apply configuration changes to a running scenario
in a differential way. Children are restarted if any of their session
routes change, new children can be added to a running scenario, or
children can deliberately be removed.
Furthermore, the new version of init is able to propagate configuration
changes (modifications of <config> nodes) to its children without
restarting them.
This patch improves the accounting for the backing store of
session-state meta data. Originally, the session state used to be
allocated by a child-local heap partition fed from the child's RAM
session. However, whereas this approach was somehow practical from a
runtime's (parent's) point of view, the child component could not count
on the quota in its own RAM session. I.e., if the Child::heap grew at
the parent side, the child's RAM session would magically diminish. This
caused two problems. First, it violates assumptions of components like
init that carefully manage their RAM resources (and giving most of them
away their children). Second, if a child transfers most of its RAM
session quota to another RAM session (like init does), the child's RAM
session may actually not allow the parent's heap to grow, which is a
very difficult error condition to deal with.
In the new version, there is no Child::heap anymore. Instead, session
states are allocated from the runtime's RAM session. In order to let
children pay for these costs, the parent withdraws the local session
costs from the session quota donated from the child when the child
initiates a new session. Hence, in principle, all components on the
route of the session request take a small bite from the session quota to
pay for their local book keeping
Consequently, the session quota that ends up at the server may become
depleted more or less, depending on the route. In the case where the
remaining quota is insufficient for the server, the server responds with
'QUOTA_EXCEEDED'. Since this behavior must generally be expected, this
patch equips the client-side 'Env::session' implementation with the
ability to re-issue session requests with successively growing quota
donations.
For several of core's services (ROM, IO_MEM, IRQ), the default session
quota has now increased by 2 KiB, which should suffice for session
requests to up to 3 hops as is the common case for most run scripts. For
longer routes, the retry mechanism as described above comes into effect.
For the time being, we give a warning whenever the server-side quota
check triggers the retry mechanism. The warning may eventually be
removed at a later stage.
This patch equips init with the ability to report its internal state in
the form of a "state" report. This feature can be enabled by placing a
'<report>' node in init's configuration.
The report node accepts the following arguments (with their default
values):
'delay_ms="100"': specifies the number of milliseconds to wait before
producing a new report. This way, many consecutive state changes -
like they occur during the startup - do not result in an overly
large number of reports but are merged into one final report.
'buffer="4K"': the maximum size of the report in bytes. The attribute
accepts the use of K/M/G as units.
'init_ram="no"': if enabled, the report will contain a '<ram>' node
with the memory stats of init.
'ids="no"': supplement the children in the report with unique IDs, which
may be used to infer the lifetime of children accross configuration
updates in the future;
'requested="no"': if enabled, the report will contain information about
all session requests initiated by the children.
'provided="no"': if enabled, the report will contain information about
all sessions provided by all servers.
'session_args="no"': level of detail of the session information
generated via 'requested' or 'provided'.
'child_ram="no"': if enabled, the report will contain a '<ram>' node
for each child based on the information obtained from the child's RAM
session.
Issue #2246
This patch enhances init with the support for rewriting session labels
in the target node of a matching session route. For example, a Noux
instance may have the following session route for the "home" file
system:
<route>
<service name="File_system" label="home">
<child name="rump_fs"/>
</service>
...
</route>
At the rump_fs file-system server, the label of the file-system session
will appear as "noux -> home". This information may be evaluated by
rump_fs's server-side policy. However, when renaming the noux instance,
we'd need to update this server-side policy.
With the new mechanism, the client's identity can be hidden from the
server. The label could instead represent the role of the client, or a
name of a physical resource. For example, the Noux route could be
changed to this:
<route>
<service name="File_system" label="home">
<child name="rump_fs" label="primary_user"/>
</service>
...
</route>
When the rump_fs receives the session request, it is presented with the
label "primary_user". The fact that the client is "noux" is not taken
into account for the server-side policy selection.
Issue #2248
This commit includes changes to the Nic::Session_component interface.
We now pass the entire env to the component instead of only ram, rm and
the ep because we need the env to open connections from within the
Session_component implemenation. So far only the cadence_gem driver
needs this, though.
Issue #2280.
This patch enhances init with the ability to route individual
environment sessions. Prior this patch, environment sessions could be
routed only by an all-encompassing '<service>' node that would match
both child-initiated and environment sessions.
In contrast to the existing 'label', 'label_prefix', and 'label_suffix'
attributes of '<service>' nodes, which are always scoped with ther name
of the corresponding child, the 'unscoped_label' allows the definition
of routing rules for all session requests, including init's requests for
the child's environment sessions. For example, to route the ROM session
requests for a child's dynamic linker, the following route would match:
<route>
<service name="ROM" unscoped_label="ld.lib.so"> ... </service>
</route>
Issue #2215
This patch adds the handling of 'CHARACTER' events as emitted by the
input-filter's character generator (<chargen>). To avoid interpreting
press/release events twice (at the input filter and by the terminal's
built-in scancode tracker), the terminal's scancode tracker can be
explicitly disabled via <config> <keyboard layout="none"/> </config>.
In the future, the terminal's built-in scancode tracker will be
removed.
The use of the terminal with the input filter is illustrated by the
'terminal_echo.run' script.
Issue #2264
Character events are created via a dedicated 'Event' constructor that
takes an 'Event:Utf8' object as argument. Internally, the character is
kept in the '_code' member. The 'Utf8' value can by retrieved by the
recipient via the new 'utf8' method.
Issue #2264
The read-ready packet informs the server that the client wants to be
notified if a handle becomes readable. When becoming readable, the
server acknowledges packet and the client may queue a read requests
accordingly.
This patch eliminates the need for a global allocator by passing the
parent-service registry as argument to the 'Slave::Policy' constructor.
Fixes#2269
The support has two parts. First, a VFS plugin now gets passed an
I/O-response handler callback on construction, which informs users of the
VFS that an I/O event occurred. This enables, for example, the libC to
check if blocking read can be completed. Further, the VFS file I/O
interface provides now functions for suspendable reads, i.e.,
queue_read() and complete_read().
Replacing the node lookup table with an Id_space removes the
limit on open handles per session and allows mutal associativity
between File_system handles and local VFS handles.
Fix#2221
The new utility at 'os/static_parent_services.h' allows the creation of
a registry of parent services at compile time and thereby eliminates the need
for dynamic memory allocations whenever the set of services is known at
compile time as is the case for most uses of 'Slave::Policy'. The commit
showcases the utility in the bomb test.
This commit enables compile-time warnings displayed whenever a deprecated
API header is included, and adjusts the existing #include directives
accordingly.
Issue #1987
The init component used to create the CPU/RAM/PD/ROM sessions (the child
environment) for its children by issuing session requests to its parent,
which is typically core. This policy was hard-wired. This patch enables
the routing of the environment sessions of the children of init
according to the configured routing policy.
Because there is no hard-wired policy regarding the environment sessions
anymore, routes to respective services must be explicitly declared in
the init configuration. For this reason, the patch adjusts several run
scripts in this respect.
This patch removes the outdated '<if-args>' special handling of session
labels. The '<if-args>' feature will eventually be removed completely
(ref #2250)
Issue #2197
Issue #2215
Issue #2233
Issue #2250
This patch changes the 'Xml_node_label_score' to regard an empty
label_prefix or label_suffix as a match instead of a conflict. Until
now, there was no use case for an empty label_prefix. But with init's
new ability to route environment sessions, an empty prefix denotes any
child-initiated session (as oposed to an parent-initiated environment
session).
Issue #2215
Issue #2233
To better support non-blocking terminal components, let the
'Terminal::Session::write()' function return the number of bytes
actually written.
Fixes#2240
This patch enables warnings if one of the deprecate functions that rely
in the implicit use of the global Genode::env() accessor are called.
For the time being, some places within the base framework continue
to rely on the global function while omitting the warning by calling
'env_deprecated' instead of 'env'.
Issue #1987
Most implementations use a Signal_handler now to acknowledge the packet
instead of waiting for the transfer completion. The exceptions to that are
the non-DMA implementations for RPI and PL180
Ref #2206
At least on foc_x86_64, nic_router refused to create sessions for the
test clients as the session object's size exceeds the old quota
donation.
Ref #2139
Both methods are now available for Ipv4_address as well as for
Ipv4_address_prefix. An IPv4 address is invalid if it contains zeros only.
An IPv4 address prefix is invalid if its address is invalid and its
prefix is 32.
Ref #2139
This patch unconditionally applies the labeling of sessions and thereby
removes the most common use case of 'Child_policy::filter_session_args'.
Furthermore, the patch removes an ambiguity of the session labels of
sessions created by the parent of behalf of its child, e.g., the PD
session created as part of 'Child' now has the label "<child-name>"
whereas an unlabeled PD-session request originating from the child
has the label "<child-name> -> ". This way, the routing-policy of
'Child_policy::resolve_session_request' can differentiate both cases.
As a consequence, the stricter labeling must now be considered wherever
a precise label was specified as a key for a session route or a server-
side policy selection. The simplest way to adapt those cases is to use a
'label_prefix' instead of the 'label' attribute. Alternatively, the
'label' attribute may used by appending " -> " (note the whitespace).
Fixes#2171
This patch adjusts the various users of the 'Child' API to the changes
on the account of the new non-blocking parent interface. It also removes
the use of the no-longer-available 'Connection::KEEP_OPEN' feature.
With the adjustment, we took the opportunity to redesign several
components to fit the non-blocking execution model much better, in
particular the demo applications.
Issue #2120
This is a redesign of the root and parent interfaces to eliminate
blocking RPC calls.
- New session representation at the parent (base/session_state.h)
- base-internal root proxy mechanism as migration path
- Redesign of base/service.h
- Removes ancient 'Connection::KEEP_OPEN' feature
- Interface change of 'Child', 'Child_policy', 'Slave', 'Slave_policy'
- New 'Slave::Connection'
- Changed child-construction procedure to be compatible with the
non-blocking parent interface and to be easier to use
- The child's initial LOG session, its binary ROM session, and the
linker ROM session have become part of the child's envirenment.
- Session upgrading must now be performed via 'env.upgrade' instead
of performing a sole RPC call the parent. To make RAM upgrades
easier, the 'Connection' provides a new 'upgrade_ram' method.
Issue #2120
- use the correct memory free functions on errors
- report packet submit errors
- rename 'Usb::Packet_descriptor::transfer.timeout' as
'Usb::Packet_descriptor::transfer.polling_interval'
Fixes#2135
* Supply Env to Input::Session_component
* Attach input event dataspace at Input::Client
* Process input events by lambda rather than pointer
* Supply Env and a label to Input::Connection
* Wm serves valid input_session to decorator
* Per-source signal handling at input_merger
* Base API update for dummy_input_drv, test_input
* Input API update for launcher, menu_view, terminal,
mupdf, sdl, seoul, virtualbox
Ref #1987
In other contexts (IPv4) 'calc_checksum' merely returns a new checksum that is
then installed via 'checksum'. Thus, the UDP 'calc_checksum' that calculates AND
installs a new checksum is misleading.
Ref #114
* Unify uart drivers of different hardware drivers
* Remove deprecated IRQ activations
* Remove additional timer thread in Fiasco* KDB driver
* Move more generic UART definitions to specific supported
platforms (e.g.: pl011 -> pbxa9)
* Move internal definitions from global to local headers
Ref #1987Fix#2071
Use a seperate handle at each session.
Use SEEK_TAIL to append messages to files.
Increase packet buffer.
Refactor to component framework.
Fixes#1777
Issue #2060
Besides adapting the components to the use of base/log.h, the patch
cleans up a few base headers, i.e., it removes unused includes from
root/component.h, specifically base/heap.h and
ram_session/ram_session.h. Hence, components that relied on the implicit
inclusion of those headers have to manually include those headers now.
While adjusting the log messages, I repeatedly stumbled over the problem
that printing char * arguments is ambiguous. It is unclear whether to
print the argument as pointer or null-terminated string. To overcome
this problem, the patch introduces a new type 'Cstring' that allows the
caller to express that the argument should be handled as null-terminated
string. As a nice side effect, with this type in place, the optional len
argument of the 'String' class could be removed. Instead of supplying a
pair of (char const *, size_t), the constructor accepts a 'Cstring'.
This, in turn, clears the way let the 'String' constructor use the new
output mechanism to assemble a string from multiple arguments (and
thereby getting rid of snprintf within Genode in the near future).
To enforce the explicit resolution of the char * ambiguity, the 'char *'
overload of the 'print' function is marked as deleted.
Issue #1987
This patch adds the methods 'sigh_ack_avail()' and
'sigh_ready_to_submit()', which are needed to build asynchronously
operating file-system clients.
Fixes#2023
Conveying the ROM filename as the final label element simplifies
routing policy and session construction.
Annotations by nfeske:
This commit also changes the ROM session to use base/log.h instead of
base/printf.h, which produced build error of VirtualBox because the
vbox headers have a '#define Log', which collides with the content of
base/log.h. Hence, this commit has to take precautions to resolve this
conflict.
The commit alse refines the previous session-label change by adding a
new 'Session_label::prefix' method and removing the use of 'char const *'
from this part of the API.
Fixes#1787
Session_label constructor now takes a bare string rather than a
serialized argument buffer.
Replace all instances of previous constructor with 'label_from_args'
function.
Issue #1787
* remove all 'Genode::env()' calls
* use attached roms to read configuration
* use compoenent framework
* remove all PDBG, PINF, PWRN macros
Issue #1987Fixes#2019
* use Component::* instead of Server::*
* do not use old printf format anymore
* do not use old Genode::env()->heap() anymore
* avoid pointers where possible, and use references instead
* throw away the thread-safe variants of list and AVL tree,
nic_bridge became single-threaded in the past
* introduce Ram_session_guard instead of Allocator_guard
Issue #1987
Replace 'attribute(...).has_value("yes")`
with 'attribute_value(..., false)'.
This allows for boolean configuration to be set with values such as
"true", "false", "yes", "no", or "1", "0".
Fixes#2002
A configuration policy must match against a policy node label,
label_prefix, or label_suffix atttribute. A fallback to
<default-policy/> is provided as a label wildcard.
Fixes#1901
Allocating a packet in the packet stream without a payload is not
allowed. Therefore we have to allocate CTRL message packets, that do
not have a payload, with a bogus length instead.
This patch removes the outdates doc/architecture.txt since the
topics are covered by the book. We keep repos/os/doc/init.txt
because it contains a few details not present in the book (yet).
The patch streamlines the terminology a bit. Furthermore, it
slightly adjusts a few source-code comments to improve the book's
functional specification chapter.
