OS: Mengerti System Call - Revision history

Onnowpurbo: /* Pranala Menarik */

2013-04-07T06:44:15Z

Pranala Menarik

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 * [[Linux]]
 * [[Ubuntu]]
 * [[Linux: CLI untuk Survival]]
-* [[Sistem Operasi]]
+* [[Linux: Skema Partisi di Linux]]
 * [[Linux: Instalasi Sistem Operasi]]
-* [[Linux: Skema Partisi di Linux]]
 * [[Kernel]]
 * [[Compile Kernel]]
 * [[Compile Kernel: Konfigurasi Kernel]]
-* [[Kernel: Anatomi Kernel Source]]
-* [[OS: Linux Kernel]]
+===Remaster Linux===
 * [[OS: Parameter Kernel Default]]
 * [[OS: Kernel Scheduler]]
 * [[OS: Complete Teori Tuning Kernel Scheduler]]
 * [[OS: Complete Teori Tuning I/O Performance]]
 * [[OS: Tuning Manajemen Memory]]
-* [[OS: Tuning Kernel Scheduler]]
-* [[OS: Tuning Completely Fair Queueing CFQ I/O scheduler]]
+===Android===
-* [[OS: Tuning Completely Fair scheduler CFS]]
 * [[OS: Build in Monitoring Tool]]
 * [[Linux Benchmarking]]
 * [[OS: Benchmarking menggunakan UnixBench]]
 * [[OS: Benchmarking menggunakan LLCBench]]

Onnowpurbo: /* Pranala Menarik */

2013-04-03T06:04:41Z

Pranala Menarik

← Older revision		Revision as of 06:04, 3 April 2013
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	* [[Linux]]		* [[Linux]]
	* [[Ubuntu]]		* [[Ubuntu]]
			* [[Linux: CLI untuk Survival]]
	* [[Sistem Operasi]]		* [[Sistem Operasi]]
			* [[Linux: Instalasi Sistem Operasi]]
			* [[Linux: Skema Partisi di Linux]]
	* [[Kernel]]		* [[Kernel]]
	* [[Compile Kernel]]		* [[Compile Kernel]]
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	* [[OS: Complete Teori Tuning Kernel Scheduler]]		* [[OS: Complete Teori Tuning Kernel Scheduler]]
	* [[OS: Complete Teori Tuning I/O Performance]]		* [[OS: Complete Teori Tuning I/O Performance]]
			* [[OS: Tuning Manajemen Memory]]
	* [[OS: Tuning Kernel Scheduler]]		* [[OS: Tuning Kernel Scheduler]]
	* [[OS: Tuning Completely Fair Queueing CFQ I/O scheduler]]		* [[OS: Tuning Completely Fair Queueing CFQ I/O scheduler]]
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	* [[OS: Mengerti System Call]]		* [[OS: Mengerti System Call]]
	* [[OS: Membuat Kernel Modul]]		* [[OS: Membuat Kernel Modul]]
			* [[OS: Android - Download]]

Onnowpurbo: /* Contoh System Call */

2013-04-02T04:07:51Z

Contoh System Call

← Older revision		Revision as of 04:07, 2 April 2013
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	'''fs/read_write.c'''		'''fs/read_write.c'''

	~~This function finds the file~~ struct ~~associated with the~~ fd ~~number you passed to the~~ read() ~~function~~. ~~That structure contains a~~ pointer ~~to the~~ function ~~that should be used to read~~ data ~~from that particular kind of~~ file. ~~After doing some checks~~, ~~it calls that file-specific read~~ function ~~in order to actually~~ read ~~the~~ data ~~from the~~ file, ~~and then returns~~. ~~This~~ file~~-specific function is defined somewhere else - the~~ socket code, ~~filesystem~~ code, or device driver code, ~~for example. This is one of the points at which a specific~~ kernel ~~subsystem finally interfaces with the rest of the~~ kernel. ~~After our~~ read ~~function finishes~~, ~~we return from the~~ sys_read(), ~~back to~~ DoSyscall(), ~~which switches~~ control to ret_from_except, ~~which is in defined in~~:		Function ini akan mengambil fice struct yang berhubungan dengan nomor fd yang kita kirim ke function read(). Struct ini berisi pointer ke function yang harusnya digunakan untuk membaca data dari file tertentu. Setelah melakukan beberapa check, dia akan call function read untuk file tertentu untuk membaca data dari file, dan kemudian return. Function file spesifik ini di definisikan di tempat lain, contohnya,socket code, file system code, atau device driver code. Di titik ini, sebuah subsystem kernel yang spesifik akan berinteraksi dengan kernel secara keseluruhan. Setelah function read kita selesai, kita akan kembali dari sys_read(), kembali ke DoSyscall(), akan akan men-switch control ret_from_except, yang di definisikan di:

	'''arch/ppc/kernel/entry.S'''		'''arch/ppc/kernel/entry.S'''

	~~This checks for tasks that might need to be done before switching back to~~ user mode. ~~If nothing else needs to be done~~, ~~we fall through to the~~ restore ~~function~~, ~~which restores the~~ user ~~process's state and returns~~ control ~~back to the~~ user program. ~~There! Your~~ read() ~~call is done! If you're lucky~~, ~~you even got your~~ data ~~back~~.		Di tempat sini akan di cek task yang perlu diselesaikan sebelum switch kembali ke user mode. Jika tidak ada lagi yang perlu dilakukan, kita akan kembali ke function restore, yang akan me-restore state user proses dan mengembalikan control ke user program. Selesai sudah call ke read(). Jika kita beruntung, kita akan memperoleh data kita kembali.

	~~You can explore syscalls further by putting printks at strategic places~~. ~~Be sure to limit the amount of~~ output ~~from these printks. For example~~, ~~if you add a~~ printk to sys_read() ~~syscall~~, ~~you should do something like this~~:		Kita dapat mengeksplorasi syscall lebih dalam lagi dengan menempatkan printk pada berbagai tempat yang strategis. Pastikan untuk memberi batasan jumlah output dari printk, Contoh, kita dapat menambahkan printk ke syscall sys_read(), kita dapat menambahkan sebagai berikut:

	static int mycount = 0;		static int mycount = 0;
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	}		}

	~~Have fun~~!		Selamat menikmati!

	==Referensi==		==Referensi==

Onnowpurbo: /* Contoh System Call */

2013-04-02T03:55:40Z

Contoh System Call

← Older revision		Revision as of 03:55, 2 April 2013
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	Tabel syscall berisi address dari function yang mengimplementasikan setiap system call. Contoh, function system call read() bernama sys_read. Nomor system call read() adalah 3, oleh karenanya address dari sys_read() adalah entry ke 4 di tabel system call (karena nomor pertama system call adalah 0). Kita membaca data dari address sys_call_table + (3 * word_size) dan kita akan memperoleh address dari sys_read().		Tabel syscall berisi address dari function yang mengimplementasikan setiap system call. Contoh, function system call read() bernama sys_read. Nomor system call read() adalah 3, oleh karenanya address dari sys_read() adalah entry ke 4 di tabel system call (karena nomor pertama system call adalah 0). Kita membaca data dari address sys_call_table + (3 * word_size) dan kita akan memperoleh address dari sys_read().

	~~After~~ DoSyscall ~~has looked up the correct~~ system call ~~address~~, ~~it transfers control to that~~ system call. ~~Let's look at where~~ sys_read() ~~is defined~~, ~~in the~~ file:		Setelah DoSyscall diperoleh address system call yang benar, dia akan mentransfer kontrol ke system call tersebut. Mari kita lihat dimana sys_read() di definisikan, dalam file:

	'''fs/read_write.c'''		'''fs/read_write.c'''

Onnowpurbo: /* Contoh System Call */

2013-04-02T03:36:16Z

Contoh System Call

← Older revision		Revision as of 03:36, 2 April 2013
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	'''arch/ppc/kernel/misc.S'''		'''arch/ppc/kernel/misc.S'''

	~~The~~ syscall ~~table contains the addresses of the functions that implement each~~ system call. ~~For example~~, ~~the~~ read() system call ~~function is named sys_read. The~~ read() ~~system call number is~~ 3, ~~so the~~ address of sys_read() ~~is in the 4th~~ entry ~~of the~~ system call ~~table~~ (~~since we start numbering the~~ system ~~calls with~~ 0). ~~We read the~~ data ~~from the~~ address sys_call_table + (3 * word_size) ~~and we get the~~ address of sys_read().		Tabel syscall berisi address dari function yang mengimplementasikan setiap system call. Contoh, function system call read() bernama sys_read. Nomor system call read() adalah 3, oleh karenanya address dari sys_read() adalah entry ke 4 di tabel system call (karena nomor pertama system call adalah 0). Kita membaca data dari address sys_call_table + (3 * word_size) dan kita akan memperoleh address dari sys_read().

	After DoSyscall has looked up the correct system call address, it transfers control to that system call. Let's look at where sys_read() is defined, in the file:		After DoSyscall has looked up the correct system call address, it transfers control to that system call. Let's look at where sys_read() is defined, in the file:

Onnowpurbo: /* Contoh System Call */

2013-04-02T03:30:34Z

Contoh System Call

← Older revision		Revision as of 03:30, 2 April 2013
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	'''arch/ppc/kernel/entry.S'''		'''arch/ppc/kernel/entry.S'''

	~~Eventually~~, ~~this~~ function ~~loads up the~~ address ~~of the~~ syscall ~~table and indexes into it using the~~ system call ~~number~~. ~~The~~ syscall ~~table is what the~~ OS ~~uses to translate from a~~ system call ~~number to a particular~~ system call. ~~The~~ system call ~~table is named~~ sys_call_table ~~and defined in~~:		Pada saatnya, function ini akan me-load address dari tabel syscall dan index ke address tersebut menggunakan nomor system call . Tabel syscall adalah apa yang digunakan oleh sistem operasi (OS) untuk menterjemahkan nomor system call ke system call tertentu. Tabel system call bernama sys_call_table didefinisikan di:

	'''arch/ppc/kernel/misc.S'''		'''arch/ppc/kernel/misc.S'''

Onnowpurbo: /* Lebih detail tentang System call */

2013-04-02T03:25:21Z

Lebih detail tentang System call

← Older revision		Revision as of 03:25, 2 April 2013
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	Instruksi di alamat yang baru akan menyimpan state user program, menentukan sistem call apa yang kita inginkan, kemudian call fuction tersebut di kernel yang mengimplementasikan system call, setelah selesai maka mengembalikan program state, dan kembali ke user program. Sebuah system call adalah salah satu cara agar function yang di definisikan dalam device driver untuk bisa di panggil.		Instruksi di alamat yang baru akan menyimpan state user program, menentukan sistem call apa yang kita inginkan, kemudian call fuction tersebut di kernel yang mengimplementasikan system call, setelah selesai maka mengembalikan program state, dan kembali ke user program. Sebuah system call adalah salah satu cara agar function yang di definisikan dalam device driver untuk bisa di panggil.

			Bagi yang ingin mendalami lebih lanjut, di persilahkan untuk membaca selanjutnya.

	==Contoh System Call==		==Contoh System Call==

Onnowpurbo at 03:16, 2 April 2013

2013-04-02T03:16:35Z

← Older revision		Revision as of 03:16, 2 April 2013
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	.long ret		.long ret

	li ~~stands for~~ "load immediate", ~~which means that a constant value known at~~ compile ~~time is stored in a~~ register. ~~First~~, trap ~~is loaded into the~~ register r10. ~~On the next line~~, ~~that value is stored on the~~ address ~~given by~~ TRAP(r11). TRAP(r11) ~~and the next two lines do some hardware specific~~ bit ~~manipulation. After that we call the tfer function (i.e. the transfer_to_handler function)~~, ~~which does yet more~~ housekeeping, ~~and then transfers control to hdlr (i.e. DoSyscall). Note that transfer_to_handler loads the address of the handler from the link~~ register, ~~which is why you see~~ .long DoSyscall ~~instead of~~ bl DoSyscall.		li singkatan dari "load immediate", yang berarti nilai kontanta yang diketahui saat waktu compile di simpan di register. Pertama kali, trap di load ke register r10. Di kalimat selanjutnya, nilai tersebut di simpan ke address yang diberikan oleh TRAP(r11). TRAP(r11) dan dua kalimat selanjutnya melakukan manipulasi bit spesifik, yang pada dasarnya melakukan housekeeping, dan kemudian men-transfer kontrol ke register, oleh karenanya kita akan melihat .long DoSyscall bukan bl DoSyscall.

	~~Now~~, ~~let's look at~~ DoSyscall. ~~It's in the~~ file:		Selanjutnya, mari kita lihat DoSyscall. Ini ada di file:

	'''arch/ppc/kernel/entry.S'''		'''arch/ppc/kernel/entry.S'''

Onnowpurbo: /* A system call example */

2013-04-02T02:57:06Z

A system call example

← Older revision		Revision as of 02:57, 2 April 2013
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	Instruksi di alamat yang baru akan menyimpan state user program, menentukan sistem call apa yang kita inginkan, kemudian call fuction tersebut di kernel yang mengimplementasikan system call, setelah selesai maka mengembalikan program state, dan kembali ke user program. Sebuah system call adalah salah satu cara agar function yang di definisikan dalam device driver untuk bisa di panggil.		Instruksi di alamat yang baru akan menyimpan state user program, menentukan sistem call apa yang kita inginkan, kemudian call fuction tersebut di kernel yang mengimplementasikan system call, setelah selesai maka mengembalikan program state, dan kembali ke user program. Sebuah system call adalah salah satu cara agar function yang di definisikan dalam device driver untuk bisa di panggil.

	==~~A system call example~~==		==Contoh System Call==

	~~This is a good place to start showing~~ code ~~to go along with the theory~~. ~~We'll follow the progress of a~~ read() ~~system call~~, ~~starting from the moment the~~ system call ~~instruction is executed~~. ~~The~~ PowerPC ~~architecture will be used as an example for the architecture specific part of the~~ code. ~~On the~~ PowerPC, ~~when you execute a~~ system call, ~~the~~ processor ~~jumps to the~~ address 0xc00. ~~The code at that location is defined in the~~ file:		Berikut kita akan mulai memperlihatkan code beserta sedikit teorinya. Kita akan mengikuti gerakan dari system call read(), mulai dari instruksi system call di jalankan. Arsitektur PowerPC akan digunakan sebagai contoh dari code yang spesifik arsitektur. Di PowerPC, saat kita menjalankan system call, processor akan jump ke address 0xc00. Code pada lokasi ini di definisikan pada file:
	~~arch/ppc/kernel/head.S~~

	~~It looks something like this~~:		arch/ppc/kernel/head.S

			Ini akan tampak seperti:

	/* System call */		/* System call */
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	EXCEPTION(0xe00, Trap_0e, UnknownException, EXC_XFER_EE)		EXCEPTION(0xe00, Trap_0e, UnknownException, EXC_XFER_EE)

	~~What this~~ code ~~does is save some~~ state ~~and~~ call ~~another~~ function ~~called~~ DoSyscall. ~~Here's a more detailed explanation (feel free to skip this part)~~:		Yang akan dilakukan oleh code ini adalah menyimpan state program, dan call function DoSyscall. Berikut adalah penjelasan lebih detail:

			* EXCEPTION_PROLOG adalah sebuah macro yang akan menangani switch dari user ke kernel space, yang akan melakukan hal seperti menyimpan kondisi register dari proses user.

	~~EXCEPTION_PROLOG is a macro that handles the switch from user to kernel space, which requires things like saving the register state of the user process.~~ EXC_XFER_EE_LITE ~~is called with the~~ address ~~of this routine~~, ~~and the~~ address ~~of the~~ function DoSyscall. ~~Eventually~~, ~~some state will be saved and~~ DoSyscall ~~will be called~~. ~~The next two lines save two~~ exception ~~vectors on the addresses~~ 0xd00 ~~and~~ 0xe00.		* EXC_XFER_EE_LITE akan dipanggil menggunakan address dari route tersebut, dan address dari function DoSyscall. Pada suatu saat, register akan di simpan dan DoSyscall akan di panggil. Dua kalimat selanjutnya adalah exception vector pada address 0xd00 dan 0xe00.

	EXC_XFER_EE_LITE ~~looks like this~~:		EXC_XFER_EE_LITE akan tampak sebagai berikut:

	#define EXC_XFER_EE_LITE(n, hdlr) \		#define EXC_XFER_EE_LITE(n, hdlr) \
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	ret_from_except)		ret_from_except)

	EXC_XFER_TEMPLATE ~~is another~~ macro, ~~and the~~ code ~~looks like this~~:		EXC_XFER_TEMPLATE adalah macro, dan code akan tampak sebagai berikut:

	#define EXC_XFER_TEMPLATE(n, hdlr, trap, copyee, tfer, ret) \		#define EXC_XFER_TEMPLATE(n, hdlr, trap, copyee, tfer, ret) \
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	Now, let's look at DoSyscall. It's in the file:		Now, let's look at DoSyscall. It's in the file:

	arch/ppc/kernel/entry.S		'''arch/ppc/kernel/entry.S'''

	Eventually, this function loads up the address of the syscall table and indexes into it using the system call number. The syscall table is what the OS uses to translate from a system call number to a particular system call. The system call table is named sys_call_table and defined in:		Eventually, this function loads up the address of the syscall table and indexes into it using the system call number. The syscall table is what the OS uses to translate from a system call number to a particular system call. The system call table is named sys_call_table and defined in:

	arch/ppc/kernel/misc.S		'''arch/ppc/kernel/misc.S'''

	The syscall table contains the addresses of the functions that implement each system call. For example, the read() system call function is named sys_read. The read() system call number is 3, so the address of sys_read() is in the 4th entry of the system call table (since we start numbering the system calls with 0). We read the data from the address sys_call_table + (3 * word_size) and we get the address of sys_read().		The syscall table contains the addresses of the functions that implement each system call. For example, the read() system call function is named sys_read. The read() system call number is 3, so the address of sys_read() is in the 4th entry of the system call table (since we start numbering the system calls with 0). We read the data from the address sys_call_table + (3 * word_size) and we get the address of sys_read().

	After DoSyscall has looked up the correct system call address, it transfers control to that system call. Let's look at where sys_read() is defined, in the file:		After DoSyscall has looked up the correct system call address, it transfers control to that system call. Let's look at where sys_read() is defined, in the file:
	fs/read_write.c
			'''fs/read_write.c'''

	This function finds the file struct associated with the fd number you passed to the read() function. That structure contains a pointer to the function that should be used to read data from that particular kind of file. After doing some checks, it calls that file-specific read function in order to actually read the data from the file, and then returns. This file-specific function is defined somewhere else - the socket code, filesystem code, or device driver code, for example. This is one of the points at which a specific kernel subsystem finally interfaces with the rest of the kernel. After our read function finishes, we return from the sys_read(), back to DoSyscall(), which switches control to ret_from_except, which is in defined in:		This function finds the file struct associated with the fd number you passed to the read() function. That structure contains a pointer to the function that should be used to read data from that particular kind of file. After doing some checks, it calls that file-specific read function in order to actually read the data from the file, and then returns. This file-specific function is defined somewhere else - the socket code, filesystem code, or device driver code, for example. This is one of the points at which a specific kernel subsystem finally interfaces with the rest of the kernel. After our read function finishes, we return from the sys_read(), back to DoSyscall(), which switches control to ret_from_except, which is in defined in:

	arch/ppc/kernel/entry.S		'''arch/ppc/kernel/entry.S'''

	This checks for tasks that might need to be done before switching back to user mode. If nothing else needs to be done, we fall through to the restore function, which restores the user process's state and returns control back to the user program. There! Your read() call is done! If you're lucky, you even got your data back.		This checks for tasks that might need to be done before switching back to user mode. If nothing else needs to be done, we fall through to the restore function, which restores the user process's state and returns control back to the user program. There! Your read() call is done! If you're lucky, you even got your data back.
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	Have fun!		Have fun!


	==Referensi==		==Referensi==

Onnowpurbo: /* Lebih detail tentang System call */

2013-04-02T02:27:08Z

Lebih detail tentang System call

← Older revision		Revision as of 02:27, 2 April 2013
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	Instruksi di alamat yang baru akan menyimpan state user program, menentukan sistem call apa yang kita inginkan, kemudian call fuction tersebut di kernel yang mengimplementasikan system call, setelah selesai maka mengembalikan program state, dan kembali ke user program. Sebuah system call adalah salah satu cara agar function yang di definisikan dalam device driver untuk bisa di panggil.		Instruksi di alamat yang baru akan menyimpan state user program, menentukan sistem call apa yang kita inginkan, kemudian call fuction tersebut di kernel yang mengimplementasikan system call, setelah selesai maka mengembalikan program state, dan kembali ke user program. Sebuah system call adalah salah satu cara agar function yang di definisikan dalam device driver untuk bisa di panggil.


	That was the whirlwind tour of how a system call works. Next, we'll go into minute detail for those who are curious about exactly how the kernel does all this. Don't worry if you don't quite understand all of the details - just remember that this is one way that a function in the kernel can end up being called, and that no magic is involved. You can trace the control flow all the way through the kernel - with difficulty sometimes, but you can do it.

	==A system call example==		==A system call example==