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Merge tag 'sound-4.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai...
[linux-2.6-block.git] / Documentation / magic-number.txt
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LT		 1This file is a registry of magic numbers which are in use. When you
2add a magic number to a structure, you should also add it to this
3file, since it is best if the magic numbers used by various structures
4are unique.
5
6It is a *very* good idea to protect kernel data structures with magic
7numbers. This allows you to check at run time whether (a) a structure
8has been clobbered, or (b) you've passed the wrong structure to a
9routine. This last is especially useful --- particularly when you are
10passing pointers to structures via a void * pointer. The tty code,
11for example, does this frequently to pass driver-specific and line
12discipline-specific structures back and forth.
13
14The way to use magic numbers is to declare then at the beginning of
15the structure, like so:
16
17struct tty_ldisc {
18 int magic;
19 ...
20};
21
22Please follow this discipline when you are adding future enhancements
23to the kernel! It has saved me countless hours of debugging,
24especially in the screwy cases where an array has been overrun and
25structures following the array have been overwritten. Using this
26discipline, these cases get detected quickly and safely.
27
28 Theodore Ts'o
29 31 Mar 94
30
31The magic table is current to Linux 2.1.55.
32
33 Michael Chastain
34 <mailto:mec@shout.net>
35 22 Sep 1997
36
37Now it should be up to date with Linux 2.1.112. Because
38we are in feature freeze time it is very unlikely that
39something will change before 2.2.x. The entries are
40sorted by number field.
41
42 Krzysztof G. Baranowski
43 <mailto: kgb@knm.org.pl>
44 29 Jul 1998
45
46Updated the magic table to Linux 2.5.45. Right over the feature freeze,
47but it is possible that some new magic numbers will sneak into the
48kernel before 2.6.x yet.
49
50 Petr Baudis
51 <pasky@ucw.cz>
52 03 Nov 2002
53
54Updated the magic table to Linux 2.5.74.
55
56 Fabian Frederick
57 <ffrederick@users.sourceforge.net>
58 09 Jul 2003
59
60
61Magic Name Number Structure File
62===========================================================================
63PG_MAGIC 'P' pg_{read,write}_hdr include/linux/pg.h
64CMAGIC 0x0111 user include/linux/a.out.h
65MKISS_DRIVER_MAGIC 0x04bf mkiss_channel drivers/net/mkiss.h
1da177e4 66HDLC_MAGIC 0x239e n_hdlc drivers/char/n_hdlc.c
25eb650a 67APM_BIOS_MAGIC 0x4101 apm_user arch/x86/kernel/apm_32.c
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LT		 68CYCLADES_MAGIC 0x4359 cyclades_port include/linux/cyclades.h
69DB_MAGIC 0x4442 fc_info drivers/net/iph5526_novram.c
70DL_MAGIC 0x444d fc_info drivers/net/iph5526_novram.c
71FASYNC_MAGIC 0x4601 fasync_struct include/linux/fs.h
72FF_MAGIC 0x4646 fc_info drivers/net/iph5526_novram.c
73ISICOM_MAGIC 0x4d54 isi_port include/linux/isicom.h
74PTY_MAGIC 0x5001 drivers/char/pty.c
75PPP_MAGIC 0x5002 ppp include/linux/if_pppvar.h
76SERIAL_MAGIC 0x5301 async_struct include/linux/serial.h
77SSTATE_MAGIC 0x5302 serial_state include/linux/serial.h
78SLIP_MAGIC 0x5302 slip drivers/net/slip.h
79STRIP_MAGIC 0x5303 strip drivers/net/strip.c
80X25_ASY_MAGIC 0x5303 x25_asy drivers/net/x25_asy.h
81SIXPACK_MAGIC 0x5304 sixpack drivers/net/hamradio/6pack.h
82AX25_MAGIC 0x5316 ax_disp drivers/net/mkiss.h
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LT		 83TTY_MAGIC 0x5401 tty_struct include/linux/tty.h
84MGSL_MAGIC 0x5401 mgsl_info drivers/char/synclink.c
85TTY_DRIVER_MAGIC 0x5402 tty_driver include/linux/tty_driver.h
86MGSLPC_MAGIC 0x5402 mgslpc_info drivers/char/pcmcia/synclink_cs.c
87TTY_LDISC_MAGIC 0x5403 tty_ldisc include/linux/tty_ldisc.h
88USB_SERIAL_MAGIC 0x6702 usb_serial drivers/usb/serial/usb-serial.h
3396c782 89FULL_DUPLEX_MAGIC 0x6969 drivers/net/ethernet/dec/tulip/de2104x.c
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LT		 90USB_BLUETOOTH_MAGIC 0x6d02 usb_bluetooth drivers/usb/class/bluetty.c
91RFCOMM_TTY_MAGIC 0x6d02 net/bluetooth/rfcomm/tty.c
92USB_SERIAL_PORT_MAGIC 0x7301 usb_serial_port drivers/usb/serial/usb-serial.h
93CG_MAGIC 0x00090255 ufs_cylinder_group include/linux/ufs_fs.h
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LT		 94RPORT_MAGIC 0x00525001 r_port drivers/char/rocket_int.h
95LSEMAGIC 0x05091998 lse drivers/fc4/fc.c
96GDTIOCTL_MAGIC 0x06030f07 gdth_iowr_str drivers/scsi/gdth_ioctl.h
97RIEBL_MAGIC 0x09051990 drivers/net/atarilance.c
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LT		 98NBD_REQUEST_MAGIC 0x12560953 nbd_request include/linux/nbd.h
99RED_MAGIC2 0x170fc2a5 (any) mm/slab.c
100BAYCOM_MAGIC 0x19730510 baycom_state drivers/net/baycom_epp.c
101ISDN_X25IFACE_MAGIC 0x1e75a2b9 isdn_x25iface_proto_data
102 drivers/isdn/isdn_x25iface.h
103ECP_MAGIC 0x21504345 cdkecpsig include/linux/cdk.h
104LSOMAGIC 0x27091997 lso drivers/fc4/fc.c
105LSMAGIC 0x2a3b4d2a ls drivers/fc4/fc.c
106WANPIPE_MAGIC 0x414C4453 sdla_{dump,exec} include/linux/wanpipe.h
107CS_CARD_MAGIC 0x43525553 cs_card sound/oss/cs46xx.c
108LABELCL_MAGIC 0x4857434c labelcl_info_s include/asm/ia64/sn/labelcl.h
109ISDN_ASYNC_MAGIC 0x49344C01 modem_info include/linux/isdn.h
110CTC_ASYNC_MAGIC 0x49344C01 ctc_tty_info drivers/s390/net/ctctty.c
111ISDN_NET_MAGIC 0x49344C02 isdn_net_local_s drivers/isdn/i4l/isdn_net_lib.h
112SAVEKMSG_MAGIC2 0x4B4D5347 savekmsg arch/*/amiga/config.c
1da177e4 113CS_STATE_MAGIC 0x4c4f4749 cs_state sound/oss/cs46xx.c
2109a2d1 114SLAB_C_MAGIC 0x4f17a36d kmem_cache mm/slab.c
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LT		 115COW_MAGIC 0x4f4f4f4d cow_header_v1 arch/um/drivers/ubd_user.c
116I810_CARD_MAGIC 0x5072696E i810_card sound/oss/i810_audio.c
117TRIDENT_CARD_MAGIC 0x5072696E trident_card sound/oss/trident.c
a786a7c0 118ROUTER_MAGIC 0x524d4157 wan_device [in wanrouter.h pre 3.9]
1da177e4 119SAVEKMSG_MAGIC1 0x53415645 savekmsg arch/*/amiga/config.c
07983f0e 120GDA_MAGIC 0x58464552 gda arch/mips/include/asm/sn/gda.h
1da177e4 121RED_MAGIC1 0x5a2cf071 (any) mm/slab.c
b9668776 122EEPROM_MAGIC_VALUE 0x5ab478d2 lanai_dev drivers/atm/lanai.c
1da177e4 123HDLCDRV_MAGIC 0x5ac6e778 hdlcdrv_state include/linux/hdlcdrv.h
1da177e4 124PCXX_MAGIC 0x5c6df104 channel drivers/char/pcxx.h
07983f0e 125KV_MAGIC 0x5f4b565f kernel_vars_s arch/mips/include/asm/sn/klkernvars.h
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LT		 126I810_STATE_MAGIC 0x63657373 i810_state sound/oss/i810_audio.c
127TRIDENT_STATE_MAGIC 0x63657373 trient_state sound/oss/trident.c
128M3_CARD_MAGIC 0x646e6f50 m3_card sound/oss/maestro3.c
129FW_HEADER_MAGIC 0x65726F66 fw_header drivers/atm/fore200e.h
130SLOT_MAGIC 0x67267321 slot drivers/hotplug/cpqphp.h
131SLOT_MAGIC 0x67267322 slot drivers/hotplug/acpiphp.h
132LO_MAGIC 0x68797548 nbd_device include/linux/nbd.h
133OPROFILE_MAGIC 0x6f70726f super_block drivers/oprofile/oprofilefs.h
134M3_STATE_MAGIC 0x734d724d m3_state sound/oss/maestro3.c
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LT		 135VMALLOC_MAGIC 0x87654320 snd_alloc_track sound/core/memory.c
136KMALLOC_MAGIC 0x87654321 snd_alloc_track sound/core/memory.c
137PWC_MAGIC 0x89DC10AB pwc_device drivers/usb/media/pwc.h
138NBD_REPLY_MAGIC 0x96744668 nbd_reply include/linux/nbd.h
1da177e4 139ENI155_MAGIC 0xa54b872d midway_eprom drivers/atm/eni.h
31a203df 140CODA_MAGIC 0xC0DAC0DA coda_file_info fs/coda/coda_fs_i.h
1da177e4 141DPMEM_MAGIC 0xc0ffee11 gdt_pci_sram drivers/scsi/gdth.h
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LT		 142YAM_MAGIC 0xF10A7654 yam_port drivers/net/hamradio/yam.c
143CCB_MAGIC 0xf2691ad2 ccb drivers/scsi/ncr53c8xx.c
144QUEUE_MAGIC_FREE 0xf7e1c9a3 queue_entry drivers/scsi/arm/queue.c
145QUEUE_MAGIC_USED 0xf7e1cc33 queue_entry drivers/scsi/arm/queue.c
146HTB_CMAGIC 0xFEFAFEF1 htb_class net/sched/sch_htb.c
07983f0e 147NMI_MAGIC 0x48414d4d455201 nmi_s arch/mips/include/asm/sn/nmi.h
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LT		 148
149Note that there are also defined special per-driver magic numbers in sound
150memory management. See include/sound/sndmagic.h for complete list of them. Many
151OSS sound drivers have their magic numbers constructed from the soundcard PCI
152ID - these are not listed here as well.
153
154IrDA subsystem also uses large number of own magic numbers, see
155include/net/irda/irda.h for a complete list of them.
156
157HFS is another larger user of magic numbers - you can find them in
158fs/hfs/hfs.h.
Linux 6.x block layer and io_uring tree(s)