Dear seL4 developers,
first, I'd like to thank you for publishing seL4 under GPL. I am very
happy that I can finally get my hands dirty with working with the kernel
of your group. :-) Currently, I am taking the first baby steps to bring
the Genode OS framework (http://genode.org) to seL4. For reference, I am
using the experimental branch.
The first smallish issue I stumbled upon stems from the fact that Genode
is written in C++. By compiling the seL4 syscall bindings with a C++
compiler, I got the following error:
error: inconsistent operand constraints in an ‘asm’
It can be reproduced by putting the following code snippet into a cc
file and compiling it with 'g++ -m32 -c' (tested with the Genode tool
chain as well as with GCC 4.8.1):
typedef enum {
seL4_SysDebugPutChar = -9,
_enum_pad_seL4_Syscall_ID = (1U << ((sizeof(int)*8) - 1))
} seL4_Syscall_ID;
void
seL4_DebugPutChar(char c)
{
asm volatile (
"pushl %%ebp \n"
"movl %%esp, %%ecx \n"
"leal 1f, %%edx \n"
"1: \n"
"sysenter \n"
"popl %%ebp \n"
:
: "a" (seL4_SysDebugPutChar),
"b" (c)
: "%ecx", "%edx", "%esi", "%edi", "memory"
);
}
When compiling the same code snippet with 'gcc' instead of 'g++',
everything is fine. It turns out that the C++ compiler does not like the
enum value to be specified as input argument. I found the following ways
to circumvent this problem:
* Changing the enum value 'SysDebugPutChar' to a positive value,
* Removing the definition of '_enum_pad_seL4_Syscall_ID',
* Casting 'seL4_SysDebugPutChar' to an integer:
: "a" ((int)seL4_SysDebugPutChar),
In any case, I seem to have to change the bindings. Do you see a way
around it? If not, would you consider one of the solutions above for the
seL4 headers?
On another note, I noticed that the bindings use the EBX register.
Unfortunately, this makes it impossible to compile seL4 userland
software as position-independent code (PIC). E.g., when compiling the
above code snippet via 'g++ -m32 -fPIC -c', the following error occurs:
error: inconsistent operand constraints in an ‘asm’
However, PIC is required in order to use shared libraries. The solution
would be to not use EBX to pass arguments to the 'asm' statements, save
EBX on the stack prior moving the respective kernel argument to the
register, and, of course, restoring it after sysenter returns.
Before I start changing the bindings, I'd like to know: is there anyone
else working on the same problem? Would you be open to accept a change
of the bindings to become PIC compliant on the costs of a few added
instructions? Or do you have another suggestion how I should go about it?
Best regards
Norman
--
Dr.-Ing. Norman Feske
Genode Labs
http://www.genode-labs.com · http://genode.org
Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden
Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth
I just noticed the web page says
"we have Haskell sort-of running on seL4 (thanks or
friends from Galois for their help), should be released
in the near future"
This is great news. Are you able to share any details
such as when any of this will be public, what the
porting strategy was (is this similar to HalVM?),
what dependencies haskell compiled code requires,
if there are sel4 bindings, etc?
Tim
Introducing seL4 2.0.0
======================
Version 2.0.0 introduces more consistent terminology to manual and code,
as well as API and performance improvements, including to seL4's
formally verified ARMv6 version.
We clarified the notion of signals and notifications vs IPC, and added a
new feature to the seL4 API that allows user programs to receive
notifications while waiting for IPC messages. You can now also poll
notification objects. Both of these changes are aimed at simplifying
user-level interaction with interrupts.
In addition to the new features, seL4 has become even faster than it was
before, esp. in scheduling threads.
The new features and performance improvements are available on all
supported platforms, and are formally verified to full sel4 standards.
We have also switched our release process to semantic versioning, so
it's easy to tell which seL4 releases are binary-compatible,
source-compatible, or will require updates to user-level code.
Terminology Changes
===================
IPC vs Notifications
--------------------
The old terminology of "synchronous IPC" vs "asynchronous IPC" was
confusing and misleading. We changed this to reflect the fact that IPC
in seL4 is always synchronous and is simply referred to as "IPC", which
is enabled by "endpoint" objects. The receive operation is now more
appropriately called "receive".
What used to be called incorrectly "asynchronous IPC" is now called
Notifications, enabled by "notification" objects. Notifications are not
a form of message passing, but arrays of binary semaphores, and the new
terminology describes this better. The operations on them are
consequently called "signal" and "wait"
New Features
============
Notification binding
--------------------
A notification can be bound to a thread and is referred to as the
thread's bound notification object. This is a 1:1 relationship.
Whenever a thread waits for an IPC on an endpoint, it will receive any
signals sent to its bound notification object, with the signal flags
converted into a single-word message.
Threads can also explicitly wait for signals by waiting on the
notification object itself.
For more details, see the 2.0.0 manual
Implementation improvements
===========================
* introduces the bitfield scheduler: faster scheduler (Was linear in the
number of runnable threads, now log n)
* improved benchmarking macros: can now specify multiple benchmarking
tracepoints at once
added CONFIG_RELEASE_PRINTF in addition to CONFIG_DEBUG and
CONFIG_RELEASE, which enables printf in a release build
API Changes
===========
* seL4_Recv replaces seL4_Wait on endpoints
* seL4_Wait is now only used on notification objects
* Async endpoint -> notification object
* sync endpoint -> endpoint
* seL4_Recv on an endpoint may now return signals sent to a thread's
bound notification object.
API Additions
=============
* seL4_NotificationObject replaces deprecated seL4_AsyncEndpointObject
* seL4_NotificationBits size in bits of a notification object
* seL4_IRQHandler_SetNotification replaces deprecated
seL4_IRQHandler_SetEndpoint
* seL4_Recv replaces seL4_Wait for endpoints
* seL4_Wait used on notifications
* seL4_NBRecv non-blocking (polling) receive on an endpoint, which fails
if there is no message waiting. Opposite of NBSend (which silently fails
if there is no receiver waiting)
* seL4_Poll collects any signals from a notification objects, returns
zero if there are none
* seL4_Signal replaces deprecated seL4_Notify
* seL4_TCB_BindNotification bind a notification to a tcb
* seL4_TCB_UnbindNotification unbind a notification from a tcb
Deprecations
============
* seL4_AsyncEndpointObject
* seL4_Notify
* seL4_IRQHandler_SetEndpoint
Note on Syscall names
====================
Logically there are only two operations on capabilities, send and
receive, which can take opcodes specifying sup-operations. For example,
the Notification operations Signal and Wait are mapped to Send and
Receive, respectively. For efficiency reasons, many kernel objects use
separate kernel entry points for their operations. You must not rely on
either, as this can change at any time. Instead, always use the
object-specific wrapper functions.
User-level repositories
=======================
To simply repository management we have merged many of our user level
library repositories. To see the changes please compare 1.0.4.xml and
2.0.x.xml in https://github.com/seL4/seL4test-manifest
Upgrade notes
=============
Calls to seL4_Wait no longer return a seL4_MessageInfo_t as seL4_Wait is
intended to be used on notification objects. Calls to the prior version
of seL4_Wait need to be replaced with seL4_Recv.
If you don't want to upgrade yet - don't worry. Both the
sel4test-manifest and verification manifest repositories have manifests
titled 1.0.4.xml which point to the tips of the previously released
repositories before today. All library repositories have a branch called
'1.0.x-compatible' which are compatible with the 1.0.4 kernel.
Note that to use the new merged repositories, you must upgrade to 2.0.0.
Full changelog
==============
Use git log 1.0.4..2.0.0 in https://github.com/seL4/seL4
More details
============
See the 2.0.0 manual included in the release for detailed descriptions
of the new features. Or ask on this mailing list!
Enjoy!
________________________________
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Hi everyone,I have some questions about seL4's timer. I know seL4 is controlling the timer device. In the current release version, scheduling is tick-based, there's a periodic interrupt that feeds into the scheduler. I wanna know if seL4 support periodic thread. I want to implement a periodic process in Refos which is above seL4 kernel.And, if seL4 does not support periodic thread, could I modify the kernel scheduler? Does it influences formal verification? I find that Refos modifies _thread_state_t enumeration-type variables (kernel\include\object\structures.h ). Does it influences formal verification? Thank you so much!!
Hi,
I was trying to configure the CAmkES-vm to run the vmware configuration.
However, I get the following error.
[apps/vm] building...
/home/bryan/camkes-vm/tools/camkes/camkes.mk:125:
/home/bryan/camkes-vm/build/x86/pc99/vm/camkes-gen.mk: No such file or
directory
[GEN] camkes-gen.mk
While transforming AST: /home/bryan/camkes-vm/apps/vm/vm.camkes:4:
unresolved reference to VM
make[1]: *** [/home/bryan/camkes-vm/build/x86/pc99/vm/camkes-gen.mk] Error
255
make[1]: *** Deleting file `/home/bryan/camkes-vm/build/x86/pc99/vm/
camkes-gen.mk'
make: *** [vm] Error 2
I have seen this error before. This time, I used the "make menuconfig"
command. I go to Applications --> VMM Main Application --> Configuration. I
type in "vmware" to try and configure it. When I am back on the command
line, I type "make vmware_defconfig" and then "make silentoldconfig" and
finally "make". Where is the camkes-gen.mk file supposed to be located?
Thanks,
Bryan
Hello,
I was wondering if I can safely destroy my application root thread after I have
setup the capabilities and memory mappings for all of my other threads in the
system?
Thanks,
Robbie VanVossen
DornerWorks
Hi,
I was just wondering for the CAmkES-vm, where is the Makefile to build it?
Also, to clone the github repository, do I use "repo" or can I use "git
clone"?
Thanks,
Bryan
Where does the seL4 microkernel actually get the timing information it
needs to enforce scheduling decisions?
I can imagine some sort of interrupt or I/O access is required to get it
from the raw hardware.
How does it get from the timing hardware to the scheduling code?
Hi,
I am following the tutorial for CAmkES and had a few questions.
There is a part in the tutorial that says to "create a dependency entry in
apps/helloworld/Kbuild for your application". How exactly do you go about
creating a dependency? Do you just add it to the first line of the Kconfig
file?
Also, for the Makefile, I needed to include the camkes.mk file. However, it
was not found in the specified directory. This is the command that I
included in the Makefile: include ${SOURCE_DIR}/../../tools/common/camkes.mk
Where could I get that file? Or if someone had the contents of that file,
I could create it myself.
Thanks,
Bryan
tl;dr 8–9 Feb, free event, travel subsidies for AU/NZ students
CALL FOR PARTICIPATION
=====================================
Fourth NICTA Software Systems Summer School
http://ssrg.nicta.com.au/Events/summer/16
=====================================
Supported by: ANU and UNSW
Over two days, this summer school will feature lectures by international leaders in computer systems from industry and academia, interspersed with short student talks and poster sessions. We will emphasise a friendly and informal setting where students can learn and obtain feedback from experts. Topics include operating systems, hypervisors, virtual machines, databases, compilers, language implementation, memory management and security.
Research students may apply for participation by submitting a summary (of no more than half a page) on their research interests, indicating how it overlaps with the topic of the summer school. They may also indicate that they would like to give a short talk, although the organisers will only select a small number of student presentations. All attending students will be able to present a poster, and are strongly encouraged to use this opportunity to get feedback from world leaders!.
We will also consider submissions from final-stage undergraduate students, post-docs or academic staff, provided they explain the benefits they expect from attendance.Supervisors of attending students are particularly welcome to attend.
All submitted material must fit on a single A4 page.
COST
Attendance is free, but subject to invitation based on the submitted abstract. We will rarely reject an application from a student. Registration includes free lunches and coffee breaks during the summer school, as well as a dinner on the evening of the first day.
A limited amount of travel support will be available for students from outside NSW and the ACT. Students requesting travel support must submit a brief justification with their application. Travel support will only be available for students from Australia and New Zealand, and will not exceed the cheapest airfare from their nearest major airport to Sydney. Funds for this are limited, and we will give priority to students likely to benefit most from the summer school, i.e. students whose research is most aligned with the topic.
LOCATION
The workshop and associated activities will be held in the Computer Science & Engineering building on the UNSW Kensington (main) campus in Sydney.
KEY DATES
Abstracts Due: Monday, 23 November, 2015, via the SSSS'16 submission site
Notification: Friday, 20 November, 2015
Early applications will be notified earlier to help you with planning.
ACCOMMODATION
For participants from outside Sydney we are holding a limited number of inexpensive rooms at a college on campus. These must be booked (and deposit paid) by the end of November. Latecomers will have to find their own accommodations (there are other colleges and backpacker hostels nearby).
ORGANISERS:
Gernot Heiser (NICTA and UNSW) <gernot(a)nicta.com.au>
Steve Blackburn (ANU and NICTA) <Steve.Blackburn(a)anu.edu.au>
PRESENTERS (tentative):
• Dr Andrew Baumann, Microsoft Research, Redmond
• Prof Steve Blackburn, ANU
• Prof Douglas Carmean, Oregon State University
• Prof Luis Ceze, University of Washington, Seattle
• Prof Kevin Elphinstone, NICTA and UNSW
• Prof Alan Fekete, NICTA and Sydney University
• Dr Tim Harris, Oracle Labs, Cambridge
• Prof Gernot Heiser FACM, NICTA and UNSW, Sydney, Australia
• Prof Tony Hosking, NICTA and ANU
• Prof Gabriele Keller, NICTA and UNSW • Prof Eliot Moss FACM, UMass Amherst
• Dr Karin Strauss, Microsoft Research, Redmond
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