Ensure that the timer does not handle timeouts again within 1000
microseconds after the last handling of timeouts. This makes denial of
service attacks harder. This commit does not limit the rate of timeout
signals handled inside the timer but it causes the timer to do it less
often. If a client continuously installs a very small timeout at the
timer it still causes a signal to be submitted to the timer each time
and some extra CPU time to be spent in the internal handling method. But
only every 1000 microseconds this internal handling causes user timeouts
to trigger.
If we would want to limit also the call of the internal handling method
to ensure that CPU time is spent beside the RPCs only every 1000
microseconds, things would get more complex. For instance, on NOVA
Time_source::schedule_timeout(0) must be called each time a new timeout
gets installed and becomes head of the scheduling queue. We cannot
simply overwrite the already running timeout with the new one.
Ref #2490
We update the alarm-scheduler time with results of
Timer::Connection::curr_time when we schedule new timeouts but when
handling the signal from the Timer server we updated the alarm-scheduler
time with the result of Timer::Connection::elapsed_us. Mixing times
like this could cause a non-monotone time value in the alarm scheduler.
The alarm scheduler then thought that the time value wrapped and
triggered all timeouts immediately. The problem was fixed by always
using Timer::Connection::curr_time as time source.
Ref #2490
If we add an absolute timeout to the back-end alarm-scheduler we must first
call 'handle' at the scheduler to update its internal time value.
Otherwise, it might happen that we add a timeout who's deadline is so big that
it normally belongs to the next time-counter period but the scheduler thinks
that it belongs to the current period as its time is older than the one used
to calculate the deadline.
Ref #2490
When we have two time values of an unsigned integer type and we create
the difference and want to know wether it is positive or negative within
the same value we loose at least one half of the value range for casting
to signed integers. This was the case in the alarm scheduler when
checking wether an alarm already triggered. Even worse, we casted from
'unsigned long' to 'signed int' which caused further loss on at least
x86_64. Thus, big timeouts like ~0UL falsely triggered directly.
Now, we use an extra boolean value to remember in which period of the
time counter we are and to which period of the time counter the deadline
of an alarm belongs. This boolean switches its value each time the time
counter wraps. This way, we can avoid any casting by checking wether the
current time is of the same period as the deadline of the alarm that we
inspect. If so, the alarm is pending if "current time >= alarm
deadline", otherwise it is pending if "current time < alarm deadline".
Ref #2490
When synchronizing with the remote time source, we have to take care that the
measured time difference cannot become null because its real value is smaller
than the measurement granularity. Since the granularity is one microsecond, we
simply go on polling timestamp and time until the microsecond has passed.
This busy waiting should be no problem for the system for two reasons. First,
it is limited to a relatively small amount of time and second, a busy lock
does not happen because the time source that is responsible for the limiting
factor is explicitely called on each poll.
Ref #2400
The VFS library can be used in single-threaded or multi-threaded
environments and depending on that, signals are handled by the same thread
which uses the VFS library or possibly by a different thread. If a VFS
plugin needs to block to wait for a signal, there is currently no way
which works reliably in both environments.
For this reason, this commit makes the interface of the VFS library
nonblocking, similar to the File_system session interface.
The most important changes are:
- Directories are created and opened with the 'opendir()' function and the
directory entries are read with the recently introduced 'queue_read()'
and 'complete_read()' functions.
- Symbolic links are created and opened with the 'openlink()' function and
the link target is read with the 'queue_read()' and 'complete_read()'
functions and written with the 'write()' function.
- The 'write()' function does not wait for signals anymore. This can have
the effect that data written by a VFS library user has not been
processed by a file system server yet when the library user asks for the
size of the file or closes it (both done with RPC functions at the file
system server). For this reason, a user of the VFS library should
request synchronization before calling 'stat()' or 'close()'. To make
sure that a file system server has processed all write request packets
which a client submitted before the synchronization request,
synchronization is now requested at the file system server with a
synchronization packet instead of an RPC function. Because of this
change, the synchronization interface of the VFS library is now split
into 'queue_sync()' and 'complete_sync()' functions.
Fixes#2399
The calibration of the interpolation parameters was previously only done
periodically every 500 ms. Together with the fact that the parameters
had to be stable for at least 3 calibration steps to enable
interpolation, it took at least 1.5 seconds after establishing a
connection to get microseconds-precise time values.
This is a problem for some drivers that directly start to poll time.
Thus, the timer connection now does a calibration burst as soon as it
switches to the modern mode (the mode with microseconds precision).
During this phase it does several (currently 9) calibration steps
without a delay inbetween. It is assumed that this is fast enough to not
get interrupted by scheduling. Thus, despite being small, the measured
values should be very stable which is why the burst should in most cases
be sufficient to get the interpolation initialized.
Ref #2400
When in modern mode (with local time interpolation), the timer
connection used to maximize the left shifting of its
timestamp-to-microseconds factor. The higher the shift the more precise
is the translation from timestamps to microseconds. If the timestamp
values used for determining the best shift were small - i.e. the delay
between the calibration steps were small - we may got a pretty big
shift. If we then used the shift with bigger timestamp values - i.e.
called curr_time seldom or raised calibration delays - the big shift
value became a problem. The framework had to scale down all measured
timestamps and time values temporarily to stay operative until the next
calibration step.
Thus, we now raise the shift only that much that the resulting factor
fullfills a given minimum. This keeps it as low as possible according
to the precision requirement. Currently, this requirement is set to 8
meaning that the shifted factor shall be at least 2^8 = 256.
Ref #2400
As the timer session now provides a method 'elapsed_us', there is no more need
for doing any internal calculations with values of milliseconds.
Ref #2400
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
We incorrectly used 'unsigned long' (which is 32 or 64 bit depending on
the CPU architecture) for a timestamp (which is always 64 bit) in the
timer-connection implementation.
Ref #2435
On ARM, we do not have a component-local hardware time-source. The ARM
performance counter has no reliable frequency as the ARM idle command
halts the counter. Thus, we do not do local time interpolation on ARM.
Except we're on the HW kernel. In this case we can read out the kernel
time instead.
Ref #2435
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).
Change metadata before submitting a packet. If the submitting thread is a
pthread, the metadata may be immediately change by the signal handler running
in the context of the entrypoint thread.
When a directory gets destructed it dissolves the handles of each contained file
but the acknowledgement might be still in-flight. If we finally receive it,
it leads to an Unknown_id exception on the Handles ID Space in 'handle_ack'.
Now we catch it, print a warning, and go on.
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().
The block file system wrongly modified the seek offset during a
read-modify-write operation that is required for sub-block-size
requests. This led to problems whenever such write requests spanned
multiple blocks and thereby were handled in multiple iterations.
Fixes#2262
This commit enables compile-time warnings displayed whenever a deprecated
API header is included, and adjusts the existing #include directives
accordingly.
Issue #1987
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
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
The log plugin can now be configured to request a log session with the
specified label like follows.
<log label="..."/>
Per default, no new log session is requested but the existing log
session of the component's environment is used.
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
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
It turns out that the name function does not have much use in practice
except for naming the thread of the component's initial entrypoint. For
dynamically linked components, this thread is created by the dynamic
linker. It is named "ep" in these cases. Considering that we will
eventually turn all regular components into dynamically linked
executables, the additional information provided by the
Component::name() function remains unused. So it is better to not bother
the component developers with adding boilerplate code.
The original 'Env' interface as returned by 'Genode::env()' has been
renamed to 'Env_deprecated' and moved to deprecated/env.h. The new version
of base/env.h contains the interface passed to modern components that
use the component API via base/component.h.
Issue #1832
This commit introduces the new `Component` interface in the form of the
headers base/component.h and base/entrypoint.h. The os/server.h API
has become merely a compatibilty wrapper and will eventually be removed.
The same holds true for os/signal_rpc_dispatcher.h. The mechanism has
moved to base/signal.h and is now called 'Signal_handler'.
Since the patch shuffles headers around, please do a 'make clean' in the
build directory.
Issue #1832
In scenarios where the config ROM is loaded from a report ROM or any
other non-static ROM, config might try to access an invalid dataspace
capability. This patch prevents the component from aborting in this
case.
Fixes#1914
Currently, when a signal arrives in the main thread, the signal dispatcher is
retrieved and called from the main thread, the dispatcher uses a proxy object
that in turn sends an RPC to the entry point. This becomes a problem when the
entry point destroys the dispatcher object, before the dispatch function has
been called by the main thread. Therefore, the main thread should simply send an
RPC to the entry point upon signal arrival and the dispatching should be handled
solely by the entry point.
Issue #1738
Instead of holding SPEC-variable dependent files and directories inline
within the repository structure, move them into 'spec' subdirectories
at the corresponding levels, e.g.:
repos/base/include/spec
repos/base/mk/spec
repos/base/lib/mk/spec
repos/base/src/core/spec
...
Moreover, this commit removes the 'platform' directories. That term was
used in an overloaded sense. All SPEC-relative 'platform' directories are
now named 'spec'. Other files, like for instance those related to the
kernel/architecture specific startup library, where moved from 'platform'
directories to explicit, more meaningful places like e.g.: 'src/lib/startup'.
Fix#1673
The alarm library failed to handle the case properly where an already
scheduled alarm gets rescheduled before it triggered. Even though the
attempt to reschedule the alarm (twice insertion into alarm queue) was
detected, this condition resulted in the mere modification of the
alarm's parameters while keeping the alarm's queue position unchanged.
This, in turn, may violate the invariant that all enqueued alarm objects
are strictly ordered by their deadlines. The patch handles the case by
dequeuing the alarm object before reinserting it into the queue at the
right position.
Fixes#1646
Move FS Node implementations from server/ram_fs to include/ram_fs.
Support embedded ram_fs instances in VFS configurations using <ram/>.
Add 'no space' handling to VFS symlink ops.
Fixes#1635
This patch moves the VFS file-system factory to a separate vfs library
that is independent from libc. This enables libc-less Genode programs to
easily use the VFS infrastructure.
Fixes#1561
This patch adds const qualifiers to the functions Allocator::consumed,
Allocator::overhead, Allocator::avail, and Range_allocator::valid_addr.
Fixes#1481
The way this function is currently used in dde_linux expects this
function to return. Since there is dde_kit_panic it should better
be used in such a case the output should block.
The alias is rather Linux-specific and also prevents particularly
tailored jiffies implementations. For the existing dde_linux ports (usb
and lxip) we just define jiffies to be dde_kit_timer_ticks with a
preprocessor macro.
The count value can be used to batch timeouts. I.e., if a periodic
timeout triggered multiple times before the timer had a chance to
process them, the count corresponds to the number of passed periods.
Depending on 'src_w' and 'dst_w', different lines of a block to copy may be
32-bit aligned or not, so the alignment of each line needs to get checked.
Fixes#1111.
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
