F9 Microkernel Code reading based on https://github.com/f9micro/f9-kernel

1. Part
1
:
Code
Reading
of
F9
Microkernel
ben6
2013-­‐10-­‐16

2. F9
Agenda
• Overview
of
F9-­‐Microkernel
• Code
reading
(cscope,
ctags)
• Code
trace

3. F9
Agenda
• Overview
of
F9-­‐Microkernel
• Code
reading
(cscope,
ctags)
• Code
trace

4. F9
Microkernel
Overview
• an
experimental
microkernel
used
to
construct
flexible
embedded
systems
inspired
by
famous
L4
microkernel.
• The
moMvaMon
of
F9
microkernel
is
to
deploy
modern
kernel
techniques
to
support
– running
real-­‐Mme
and
Mme-­‐sharing
applicaMons
(ex:
wireless
communicaMons)
for
ARM
Cortex-­‐M
series
microprocessors
with
efficiency
(performance
+
power
consumpMon)
– security
(memory
protecMon
+
isolated
execuMon)

5. CharacterisMcs
• F9
follows
the
fundamental
principles
of
microkernels
in
that
it
implements
address
spaces,
thread
management,
and
IPC
only
in
the
privileged
kernel.
• Designed
and
customized
for
ARM
Cortex-­‐M,
supporMng
NVIC
(Nested
Vectored
Interrupt
Controller),
Bit
Banding,
MPU
(Memory
ProtecMon
Unit)
• Energy
efficient
scheduling
and
Mckless
Mmer
• KProbes
• Independent
TCB
(Thread
Control
Block)
for
each
thread
with
its
global
ID

6. CharacterisMcs
(Cont.)
• Memory
management
– Memory
pool,
Flexible
page,
Address
space
• System
calls:
– Grant,
Map,
Flush
• UTCB
concept
–
a
small
thread-­‐specific
region
in
the
thread's
virtual
address
space,
which
is
always
mapped
• Synchronous
IPC
• Debugging
and
profiling
mechanisms

7. F9
Agenda
• Overview
of
F9-­‐Microkernel
• Code
reading
(cscope,
ctags)
• Code
trace

8. Kernel
Line
of
code
Kernel
C
code
line:
2661
Git
head:
7ae6e15bdf4d67740ef9fa2a0c6a2a194df9553b

9. cscope
• CTRL-­‐D
to
quit
• Use
arrow
key
<up>,
<down>
to
select
• Type
symbol
name
your
want
to
search

10. Use
case
of
cscope
1.
2.
3.
4.
5.
Get
f9-­‐kernel
source
code
git
clone
h=ps://github.com/f9micro/f9-­‐kernel
Generate
cscope.files
to
be
scanned
– cd
f9-­‐kernel;
find
.
-­‐name
"*.c"
-­‐o
-­‐name
"*.h"
>
cscope.files
Generate
Cscope
database
cscope
-­‐b
-­‐q
-­‐k
Using
the
database
– default
Cscope
browser
cscope
-­‐d
(be
able
to
use
vim
or
other
editor
support
cscope
database)
RegeneraHng
database
when
source
code
changes
–
Use
same
command
step
4.
Reference:
hhp://cscope.sourceforge.net/large_projects.html

11. vim
+
ctags
• sudo
apt-­‐get
install
ctags
• Generate
tags
ctags
–R
*
• key
definiMon
at
vim
CTRL
+
]
è
goto
the
funcMon
definiMon
CTRL
+
t
è
back
to
previous
funcMon
call

12. PART
1
F9
KERNEL
ENTRY

13. F9-­‐kernel
Entry
• plamorm/f9.ld
è
F9
ldscript
__l4_start

14. F9-­‐kernel
Entry
• plamorm/f9.ld
Header
of
f9.bin
is
isr_vector
table
for
Cortex-­‐M
MCU

15. f9-­‐kernel:
__l4_start
kernel/init.c
• Be
reset
handler
• F9
startup
entry

16. __l4_start
• IniMal
hooks
• Copy
data
segment
for
1st
iniMalizaMon
• Clear
segments
• IniMalize
system
clock
• Call
main()
entry

17. start.c
:
main.c
• IniMal
for
level
plamorm
hooks
• Irq
iniMal
and
disable
interrupt
• Setup
FloaMng
Point
Unit
• Show
banner
• IniMal
for
Level
kernel
hooks
• Create
and
idle
and
root
thread
• Create
Mmer
64
Mcks
for
delivering
ipc
• Init
LAST
stage
hooks
• Switch
to
iniMal
kernel
thread

18. Enable/disable
irq
inline
assembly
Syntax:
__asm__
__volaMle__("InstrucMon
List");
• __volaMle__
Tell
gcc
don’t
change
my
intrusMon
list
• cpsid,
cpsie
reference:
Implemented
interrupt
enabling
delay
in
the
Cortex-­‐M3
and
Cortex-­‐M4
processors

19. kMmer_event_create
• kMmer.c
• Create
new
event
entry
• add
to
linked
list
of
event
table
• Add
entry
for
event
scheduling

20. Switch
to
kernel
• Create
kernel
thread
and
enable
running
by
context
switch

21. F9
Agenda
• Overview
of
F9-­‐Microkernel
• Code
reading
(cscope,
ctags)
• Code
trace

22. Console
setup
before
code
trace
Pl2303
console
with
STM32F4
• USB2TTL
RX
(white)
-­‐-­‐-­‐>
PA0
• USB2TTL
TX
(green)
-­‐-­‐-­‐>
PA1
USB-­‐Serial
Controller
Prolific
2303

23. Toolchain
for
Cortex-­‐M4
• Sourcery
CodeBench
– ARM
Processors:
EABI
Release
– Verified
versions:
arm-­‐2012.03,
arm-­‐2013.05
• GNU
Tools
for
ARM
Embedded
Processors

24. stlink
Project
for
tools
we
used:
st-­‐
flash,
st-­‐uMl
hhps://github.com/texane/stlink

25. Code
trace:
st-­‐uMl
Remote
debug
port
for
gdb

26. Code
trace:
gdb
remote
target
remote
:4242

27. Code
trace
issue
• Debug
Panic
Git
HEAD:
7ae6e15bdf4d67740ef9fa2a0c6a2a194df9553b

28. Discussions
F9
?

29. References
• F9
Microkernel
source
code
and
introducMon
• Using
Cscope
on
large
projects
(example:
the
Linux
kernel)
• Ctags
wiki
• __asm__
__volaMle__
GCC的内嵌汇编语法
AT&T汇编语⾔言语法（⼀一）
• Implemented
interrupt
enabling
delay
in
the
Cortex-­‐M3
and
Cortex-­‐M4
processors
• texane's
stlink
project
at
github