?? ????? (Kernel Programming)

1
?? ?????(Kernel Programming)

• Lecture 9

2
? ?

• 1. Kernel Programming ???
• (1) Kernel Programming?
• (2) Kernel vs Application
• (3) Kernel programming ?? ??
• (4) Kernel Interface ??
• 2. System call ????
• (1) System call???
• (2) POSIX API? System calls
• (3) System call ?? ??
• (4) System call ????
• (5) System call ??

3
1. ?? ?????
4
Kernel Programming ???

• Linux kernel core ?? ??
• Linux kernel ???? ??
• Linux kernel ?? ?????

5
Kernel vs. Application (1)

• ?? ??
• Application Program ???? ????? ??
• Kernel ??????? ?? system call?? ???? ???? ????
  ?? ?????? ??

6
Kernel vs. Application (2)

• Library ??
• Application Program ?? library(C ?? ????? ?? ???
  ????? ?)? link ?? ??? ? ??.
• Kernel kernel ???? export ?? ???? ??? ? ??.
• Kernel mode vs User mode
• Application Program
• CPU? user mode?? ??
• ????? ?? ???? ?? ???? ?? ???? ?? ??? ????.
• Kernel
• CPU? kernel mode?? ??
• ?? ??? ??? ????.

7
Kernel vs. Application (3)

• Address Space
• Application Program? Kernel Program? ?? ?? ???
  ???? ??? ???, ???? ??? ?? ?? address space? ???
  ??.

8
Kernel vs. Application (4)

• Namespace pollution
• Application Program ?? ???? ??????? ? ??? ???
  ??? ???? ?? ??.
• Kernel Program ?? ???? ?? ??? ?? ????? ??? ???
  ??? ???? ??? ??? ??.

9
Kernel programming ?? ?? (1)

• Library
• stdio.h ? ?? ?? ?????? ???? ?? ??? include???
  ???.
• ?? /usr/include/linux ? /usr/include/asm ??? ???
  ???? ?? include ??.
• Namespace pollution
• ?? ??? link?? ?? ?? ??? static?? ?? ?? ?? ???
  link? symbol? symbol table ??
• EXPORT_NO_SYMBOLS
• EXPORT_SYMBOL(name)
• ?? ??? ? ??? prefix? ?? ??.
• Ex sys_open()

10
Kernel programming ?? ?? (2)

• Fault handling
• Kernel? ???? ??? ?? ??? ??? ?? ??? ????? ??? ????
  ???? ??? ?????.
• ?? ?? ?? ?? ? ?? ?? ??? ???? ???? ??.
• Address space
• ??? ???? stack? ??? ???? ??, ???? ???? ??? ???
  ????? ? ??? ?????, recursion? ?? ???? ??? ????
  ??.
• Application? data? ?? ?? ?? ??? ??(call by
  reference) ? ????? ??.

11
Kernel programming ?? ?? (3)

• ??
• ???? ?? MMX ??? ??? ? ??.

12
Kernel Interface ?? (1)

• ?? ??
• Kernel program? ???? library? ???? ??? kernel??
  export ?? ??? ?? ??? ? ??.
• Kernel interface ?? ??
• Kernel ?? ???? ?? ? kernel programming? ?? ????
  ??? ??? ?? ??? ? ??.
• Port I/O
• Interrupt
• Memory
• Synchronization
• Kernel message ??
• Device Driver registration

13
Kernel Interface ?? (2)

• I/O device ? data? ?? ?? ?? ??
• unsigned inb(unsigned port)
• Port?? 1byte? ???.
• unsigned inw(unsigned port)
• Port?? 2byte? ???.
• unsigned inl(unsigned port)
• Port?? 4byte? ???.
• unsigned outb(char value, unsigned port)
• Port? 1byte value? ??.
• unsigned outw(short int value, unsigned port)
• Port? 2byte value? ??.
• unsigned outl(long int value, unsigned port)
• Port? 4byte value? ??.

14
Kernel Interface ?? (3)

• I/O device ? data? ?? ?? ?? ?? (??)
• void insb(unsigned port, void addr, unsigned
  long count)
• Port?? count bytes? ??? ???? addr ???? ??
• void insw(unsigned port, void addr, unsigned
  long count)
• Port?? 16bit count ?? ??? ???? addr ???? ??
• void insl(unsigned port, void addr, unsigned
  long count)
• Port?? 32bit count ?? ??? ???? addr ???? ??

15
Kernel Interface ?? (4)

• I/O device ? data? ?? ?? ?? ?? (??)
• void outsb(unsigned port, void addr, unsigned
  long count)
• Memory? addr?? ???? count bytes? ??? port? ??.
• void outsw(unsigned port, void addr, unsigned
  long count)
• Memory? addr?? ???? count 16bit? ??? port? ??.
• void outsl(unsigned port, void addr, unsigned
  long count)
• Memory? addr?? ???? count 32bit? ??? port? ??.

16
Kernel Interface ?? (5)

• I/O device ? data? ?? ?? ?? ?? (??)
• Pausing I/O
• ???? ?? ??? device?? ??? ? ?? ??? ??? ? ?? ???
  ??? ??? ? ?? ??? ? ? ??.
• ?? ??? ??? ?? ?? _p ? ?? ??? ??? ???? ??.
• ?) inb() ??? ?? inb_p()

17
Kernel Interface ?? (6)

• ????? ?? ? ??? ?? ??(or ???)
• cli()/sti()
• clear/set interrupt enable
• save_flags(unsigned long flag),
  restore_flags(unsigned long flag)
• status register? ??? ???? ???? ???
• ? ???? ?? ?? ??? ?? ??? ??.
• flag? ?? ??? pass??? ???.
• int requst_irq(unsigned int irq, void
  (handler)(int), unsigned long flags, const char
  device)
• ????? IRQ? ????, ? IRQ? ?? interrupt handler? ??
• void free_irq(unsigned int irq)
• request_irq()?? ??? irq? ???

18
Kernel Interface ?? (7)

• Kernel??? ?? ??? ?? ??
• void kmalloc(unsigned int len, int priority)
• ?? ??? ??. 128131056byte?? ??
• priorityGFP_BUFFER, GFP_ATOMIC, GFP_USER,
  GFP_KERNEL
• ????? ???? ???? ????.
• void kfree(void obj)
• kmalloc()?? ?? ?? ?? ???? ??

19
Kernel Interface ?? (8)

• Kernel??? ?? ??? ?? ?? (??)
• void vmalloc(unsigned int len)
• ?? ??? ??
• ?? ?? ??
• ?? ?? ???? ???? ??? ??? ??
• void vmfree(void addr)
• vmalloc()?? ?? ?? ?? ???? ??

20
Kernel Interface ?? (9)

• ??? ??? ?? ?? ??? ???? ???? ?? ??
• unsigned long copy_from_user(void to, const void
  from, unsigned long n)
• ??? ?????? ???????? n byte?? data ??.
• unsigned long copy_to_user(void to, const void
  from, unsigned long n)
• ???????? ??? ?? ??? n byte?? data ??
• void memset(void s, char c, sizt_t count)
• ??? s? c? count?? ??(??)
• put_user(datum, ptr) / get_user(ptr)
• ??? ??? datum? ????? ???? ?? ???

21
Kernel Interface ?? (10)

• ??? ??
• void sleep_on(struct wait_queue q)
• q? ??? event? sleep??, uninterruptible
• void sleep_in_interruptible(struct wait_queue
  q)
• q? ??? event? sleep??, interruptible
• void wake_up(struct wait_queue q)
• sleep_on(q)? ?? sleep? task? wakeup
• void wake_up_interruptible(struct wait_queuq q)
• sleep_on_interruptible(q)? ?? sleep? task? wakeup

22
Kernel Interface ?? (11)

• stdout?? ?? ???? ???? ?? ??
• printk(const char fmt, .)
• printf? ?? ??
• printk(LOG_LEVELmessage string)
• LOG_LEVEL KERN_EMERG, KERN_ALERT, KERN_ERR,
  KERN_WARNING, KER_INFO, KERN_DEBUG
• ?
• printk(lt1gtHello, World)
• printk(KERN_WARNINGwarning \n)

23
Kernel Interface ?? (12)

• ???? ???? ?? ??
• int register_xxxdev(unsigned int major, const
  char name,struct file_operations fops)
• character/block driver? xxxdevmajor? ??
• xxx blk/chr
• int unregister_xxxdev(unsigned int major, const
  char name)
• xxxdevsmajor? ??? ?? device driver? ??
• int register_netdev(const char name)
• int unregister_netdev(const char name)
• MAJOR(kdev_t dev)/MINOR(kdev_t dev)
• ????dev??? major/minor ??? ??

24
2. System Call
25
System Call (1)
26
System Call (2)

• user mode process? kernel ?? interface
• user mode process? ????? kernel ??? ????? ??? ?
  ??
• ? kernel? ???? ? hardware ? ?? ?? ??
• user mode process? kernel? ??? ?? ???? ?? ???
  ????? hardware? ???? hardware? ???? ???? kernel
  ?? communication channel? ??.

27
POSIX API System calls (1)

• POSIX API (Application Programming Interface)
• ??? ????? ??? ?? ?? ??? ???? ????? ??
• application? ???? ? ???? ??? ?? ??? ??? ???? ???
  ??? ?
• ??? ?? ?? ?? ???? ?? ????? porting ?? ?? ?? ?? ??
  ?? ??
• open(), close(), read(), write() ?
• System Call
• ????? ????? ?? ??? ???? ???? ?
• Linux??? POSIX API? ???? system library ?? ???
  system call ??? ?????? ??? ?? ??? ????

28
POSIX API System calls (2)
29
System Call ?? ?? (1)

• Linux ??? system call ??
• Interrupt ?? ???? ??
• Interrupt
• ?? ??? ??? ???? ?? ? ??
• ?? ??? ???? ??? ???? ??? kerenl?? ??? ????

30
System Call ?? ?? (2)

• System call ??

31
System Call ???? (1)

• ??
• ?? kernel?? ???? ?? service? user application? ??
  ? ??? System Call ? ???
• ?? ??
• ?? ??
• System Call ?? ??
• System Call ?? ??? ??
• System Call ?? ?? ??
• Kernel ??? ? target board? ??
• user application ??
• ?? ??? System Call? ???? application ??
• library ??(??? ??? ?? ???) ? root filesystem? ??

32
System Call ???? (2)

• ? ?
• Target system? kernel source ????
• ? HOME/pxa255-pro3/kernel/linux-2.6.21
• ? ????? ???? ???? kernel? ????.

33
System Call ???? (3)

• System Call ?? ??
• Linux ??? ???? ?? ??? ??? ?? ??? ??? ??? ??.
• kernel/include/asm-arm/unistd.h ? ? ??? ??? ??
  ??? ?? ?? ??.
• ? ?? ??? system call? ???? ?? ??
• kernel/include/asm-arm/unistd.h ??? vi? ??.

34
System Call ???? (4)

• System Call ?? ?? (??)
• ??? ?? ??? System Call? ????? ??? ? ???? ???.
• unistd.h ??? ? ??? ?? ?? system call? 347?? ?? ??
  ??? ? ??. ???, ??? system call? ? ??? ?? 348???
  ????.
• __NR_? System Call ????? ???? ?????, ? ??
  mysyscall? ??? System Call ?? ???
  ????(sys_mysyscall ? ??? ?? ?? ? ??).

35
System Call ???? (5)

• System Call ???? System Call ?? ?? ??
• kernel/arch/arm/kernel/entry-common.S ?
  sys_call_table??? entry? ???? ??.
• sys_call_table?? system call ????? ?? ???? ???? ?
  ???? unistd.h? ?? ???? system call ??? ???? ??
  ????.
• ? sys_call_table? ??? System Call ???? ??
• entry-common.S ??? vi? ??.

36
System Call ???? (6)

• System Call ???? System Call ?? ?? ?? (??)
• entry-common.S ?? ??? ?? ??? ??? ? ??.
• ENTRY(sys_call_table) ??? calls.S? include?? ??.
• vi? ??? ?? calls.S? ?? ??.

37
System Call ???? (7)

• System Call ???? System Call ?? ?? ?? (??)
• calls.S ? ??? ??? ??.
• ??? ?? ??? System Call ????? ??? ? ?? ?? ???.

unistd.h? ??? ??? ??
38
System Call ???? (8)

• ?? ?? ????
• System Call ? ???? ? ??? ??? ????.
• kernel/kernel/mysyscall.c ? ??? ?? ???.

39
System Call ???? (9)

• Makefile ??
• ???? ????? ??? ??? ? ?? ?? ??? ? ? ???
  kernel/kernel/Makefile? ??? ?? ?? ??.

40
System Call ???? (10)

• Kernel ??? ?? ? ?? ??? ??
• ????? ??? ??? ?? ??? ????? ?? ??? ?? ???? ??????
  ?? ????
• cd /root/pxa255-pro3/kernel/linux-2.6.21
• make pro3_defconfig
• make oldcondig
• make uImage
• Kernel ??? ??
• U-boot bootloader? ?? ?? ??? ?? ???? ?? ???? ????
• PRO3gt run linuxf

41
System Call ??? (1)

• System Call ???? ?? user application ??
• library? ??? ?? user application? ??? ??
• ?? ???? /pxa255-pro3/test
• ??? ?? syscall_test.c

42
System Call ??? (2)

• System Call ???? ?? user application ?? (??)
• ??? ??? ?????
• ??? Header ?? ??? ???? ?????? ??

43
System Call ??? (3)

• ???
• ???? ??? ????? nfs ????? ??
• ?? ???? ???? nfs ?????? ???? ??, ??? ??? ????

44
System Call ?? ? ??? ??

• ????? ??? ???? ??? ??.

?? ??
??? ???? ??