1Linux magic numbers
2===================
3
4This file is a registry of magic numbers which are in use.  When you
5add a magic number to a structure, you should also add it to this
6file, since it is best if the magic numbers used by various structures
7are unique.
8
9It is a **very** good idea to protect kernel data structures with magic
10numbers.  This allows you to check at run time whether (a) a structure
11has been clobbered, or (b) you've passed the wrong structure to a
12routine.  This last is especially useful --- particularly when you are
13passing pointers to structures via a void * pointer.  The tty code,
14for example, does this frequently to pass driver-specific and line
15discipline-specific structures back and forth.
16
17The way to use magic numbers is to declare then at the beginning of
18the structure, like so::
19
20	struct tty_ldisc {
21		int	magic;
22		...
23	};
24
25Please follow this discipline when you are adding future enhancements
26to the kernel!  It has saved me countless hours of debugging,
27especially in the screwy cases where an array has been overrun and
28structures following the array have been overwritten.  Using this
29discipline, these cases get detected quickly and safely.
30
31Changelog::
32
33					Theodore Ts'o
34					31 Mar 94
35
36  The magic table is current to Linux 2.1.55.
37
38					Michael Chastain
39					<mailto:mec@shout.net>
40					22 Sep 1997
41
42  Now it should be up to date with Linux 2.1.112. Because
43  we are in feature freeze time it is very unlikely that
44  something will change before 2.2.x. The entries are
45  sorted by number field.
46
47					Krzysztof G. Baranowski
48					<mailto: kgb@knm.org.pl>
49					29 Jul 1998
50
51  Updated the magic table to Linux 2.5.45. Right over the feature freeze,
52  but it is possible that some new magic numbers will sneak into the
53  kernel before 2.6.x yet.
54
55					Petr Baudis
56					<pasky@ucw.cz>
57					03 Nov 2002
58
59  Updated the magic table to Linux 2.5.74.
60
61					Fabian Frederick
62					<ffrederick@users.sourceforge.net>
63					09 Jul 2003
64
65
66===================== ================ ======================== ==========================================
67Magic Name            Number           Structure                File
68===================== ================ ======================== ==========================================
69PG_MAGIC              'P'              pg_{read,write}_hdr      ``include/linux/pg.h``
70CMAGIC                0x0111           user                     ``include/linux/a.out.h``
71MKISS_DRIVER_MAGIC    0x04bf           mkiss_channel            ``drivers/net/mkiss.h``
72HDLC_MAGIC            0x239e           n_hdlc                   ``drivers/char/n_hdlc.c``
73APM_BIOS_MAGIC        0x4101           apm_user                 ``arch/x86/kernel/apm_32.c``
74CYCLADES_MAGIC        0x4359           cyclades_port            ``include/linux/cyclades.h``
75DB_MAGIC              0x4442           fc_info                  ``drivers/net/iph5526_novram.c``
76DL_MAGIC              0x444d           fc_info                  ``drivers/net/iph5526_novram.c``
77FASYNC_MAGIC          0x4601           fasync_struct            ``include/linux/fs.h``
78FF_MAGIC              0x4646           fc_info                  ``drivers/net/iph5526_novram.c``
79ISICOM_MAGIC          0x4d54           isi_port                 ``include/linux/isicom.h``
80PTY_MAGIC             0x5001                                    ``drivers/char/pty.c``
81PPP_MAGIC             0x5002           ppp                      ``include/linux/if_pppvar.h``
82SERIAL_MAGIC          0x5301           async_struct             ``include/linux/serial.h``
83SSTATE_MAGIC          0x5302           serial_state             ``include/linux/serial.h``
84SLIP_MAGIC            0x5302           slip                     ``drivers/net/slip.h``
85STRIP_MAGIC           0x5303           strip                    ``drivers/net/strip.c``
86X25_ASY_MAGIC         0x5303           x25_asy                  ``drivers/net/x25_asy.h``
87SIXPACK_MAGIC         0x5304           sixpack                  ``drivers/net/hamradio/6pack.h``
88AX25_MAGIC            0x5316           ax_disp                  ``drivers/net/mkiss.h``
89TTY_MAGIC             0x5401           tty_struct               ``include/linux/tty.h``
90MGSL_MAGIC            0x5401           mgsl_info                ``drivers/char/synclink.c``
91TTY_DRIVER_MAGIC      0x5402           tty_driver               ``include/linux/tty_driver.h``
92MGSLPC_MAGIC          0x5402           mgslpc_info              ``drivers/char/pcmcia/synclink_cs.c``
93TTY_LDISC_MAGIC       0x5403           tty_ldisc                ``include/linux/tty_ldisc.h``
94USB_SERIAL_MAGIC      0x6702           usb_serial               ``drivers/usb/serial/usb-serial.h``
95FULL_DUPLEX_MAGIC     0x6969                                    ``drivers/net/ethernet/dec/tulip/de2104x.c``
96USB_BLUETOOTH_MAGIC   0x6d02           usb_bluetooth            ``drivers/usb/class/bluetty.c``
97RFCOMM_TTY_MAGIC      0x6d02                                    ``net/bluetooth/rfcomm/tty.c``
98USB_SERIAL_PORT_MAGIC 0x7301           usb_serial_port          ``drivers/usb/serial/usb-serial.h``
99CG_MAGIC              0x00090255       ufs_cylinder_group       ``include/linux/ufs_fs.h``
100RPORT_MAGIC           0x00525001       r_port                   ``drivers/char/rocket_int.h``
101LSEMAGIC              0x05091998       lse                      ``drivers/fc4/fc.c``
102GDTIOCTL_MAGIC        0x06030f07       gdth_iowr_str            ``drivers/scsi/gdth_ioctl.h``
103RIEBL_MAGIC           0x09051990                                ``drivers/net/atarilance.c``
104NBD_REQUEST_MAGIC     0x12560953       nbd_request              ``include/linux/nbd.h``
105RED_MAGIC2            0x170fc2a5       (any)                    ``mm/slab.c``
106BAYCOM_MAGIC          0x19730510       baycom_state             ``drivers/net/baycom_epp.c``
107ISDN_X25IFACE_MAGIC   0x1e75a2b9       isdn_x25iface_proto_data ``drivers/isdn/isdn_x25iface.h``
108ECP_MAGIC             0x21504345       cdkecpsig                ``include/linux/cdk.h``
109LSOMAGIC              0x27091997       lso                      ``drivers/fc4/fc.c``
110LSMAGIC               0x2a3b4d2a       ls                       ``drivers/fc4/fc.c``
111WANPIPE_MAGIC         0x414C4453       sdla_{dump,exec}         ``include/linux/wanpipe.h``
112CS_CARD_MAGIC         0x43525553       cs_card                  ``sound/oss/cs46xx.c``
113LABELCL_MAGIC         0x4857434c       labelcl_info_s           ``include/asm/ia64/sn/labelcl.h``
114ISDN_ASYNC_MAGIC      0x49344C01       modem_info               ``include/linux/isdn.h``
115CTC_ASYNC_MAGIC       0x49344C01       ctc_tty_info             ``drivers/s390/net/ctctty.c``
116ISDN_NET_MAGIC        0x49344C02       isdn_net_local_s         ``drivers/isdn/i4l/isdn_net_lib.h``
117SAVEKMSG_MAGIC2       0x4B4D5347       savekmsg                 ``arch/*/amiga/config.c``
118CS_STATE_MAGIC        0x4c4f4749       cs_state                 ``sound/oss/cs46xx.c``
119SLAB_C_MAGIC          0x4f17a36d       kmem_cache               ``mm/slab.c``
120COW_MAGIC             0x4f4f4f4d       cow_header_v1            ``arch/um/drivers/ubd_user.c``
121I810_CARD_MAGIC       0x5072696E       i810_card                ``sound/oss/i810_audio.c``
122TRIDENT_CARD_MAGIC    0x5072696E       trident_card             ``sound/oss/trident.c``
123ROUTER_MAGIC          0x524d4157       wan_device               [in ``wanrouter.h`` pre 3.9]
124SAVEKMSG_MAGIC1       0x53415645       savekmsg                 ``arch/*/amiga/config.c``
125GDA_MAGIC             0x58464552       gda                      ``arch/mips/include/asm/sn/gda.h``
126RED_MAGIC1            0x5a2cf071       (any)                    ``mm/slab.c``
127EEPROM_MAGIC_VALUE    0x5ab478d2       lanai_dev                ``drivers/atm/lanai.c``
128HDLCDRV_MAGIC         0x5ac6e778       hdlcdrv_state            ``include/linux/hdlcdrv.h``
129PCXX_MAGIC            0x5c6df104       channel                  ``drivers/char/pcxx.h``
130KV_MAGIC              0x5f4b565f       kernel_vars_s            ``arch/mips/include/asm/sn/klkernvars.h``
131I810_STATE_MAGIC      0x63657373       i810_state               ``sound/oss/i810_audio.c``
132TRIDENT_STATE_MAGIC   0x63657373       trient_state             ``sound/oss/trident.c``
133M3_CARD_MAGIC         0x646e6f50       m3_card                  ``sound/oss/maestro3.c``
134FW_HEADER_MAGIC       0x65726F66       fw_header                ``drivers/atm/fore200e.h``
135SLOT_MAGIC            0x67267321       slot                     ``drivers/hotplug/cpqphp.h``
136SLOT_MAGIC            0x67267322       slot                     ``drivers/hotplug/acpiphp.h``
137LO_MAGIC              0x68797548       nbd_device               ``include/linux/nbd.h``
138OPROFILE_MAGIC        0x6f70726f       super_block              ``drivers/oprofile/oprofilefs.h``
139M3_STATE_MAGIC        0x734d724d       m3_state                 ``sound/oss/maestro3.c``
140VMALLOC_MAGIC         0x87654320       snd_alloc_track          ``sound/core/memory.c``
141KMALLOC_MAGIC         0x87654321       snd_alloc_track          ``sound/core/memory.c``
142PWC_MAGIC             0x89DC10AB       pwc_device               ``drivers/usb/media/pwc.h``
143NBD_REPLY_MAGIC       0x96744668       nbd_reply                ``include/linux/nbd.h``
144ENI155_MAGIC          0xa54b872d       midway_eprom	        ``drivers/atm/eni.h``
145CODA_MAGIC            0xC0DAC0DA       coda_file_info           ``fs/coda/coda_fs_i.h``
146DPMEM_MAGIC           0xc0ffee11       gdt_pci_sram             ``drivers/scsi/gdth.h``
147YAM_MAGIC             0xF10A7654       yam_port                 ``drivers/net/hamradio/yam.c``
148CCB_MAGIC             0xf2691ad2       ccb                      ``drivers/scsi/ncr53c8xx.c``
149QUEUE_MAGIC_FREE      0xf7e1c9a3       queue_entry              ``drivers/scsi/arm/queue.c``
150QUEUE_MAGIC_USED      0xf7e1cc33       queue_entry              ``drivers/scsi/arm/queue.c``
151HTB_CMAGIC            0xFEFAFEF1       htb_class                ``net/sched/sch_htb.c``
152NMI_MAGIC             0x48414d4d455201 nmi_s                    ``arch/mips/include/asm/sn/nmi.h``
153===================== ================ ======================== ==========================================
154
155Note that there are also defined special per-driver magic numbers in sound
156memory management. See ``include/sound/sndmagic.h`` for complete list of them. Many
157OSS sound drivers have their magic numbers constructed from the soundcard PCI
158ID - these are not listed here as well.
159
160IrDA subsystem also uses large number of own magic numbers, see
161``include/net/irda/irda.h`` for a complete list of them.
162
163HFS is another larger user of magic numbers - you can find them in
164``fs/hfs/hfs.h``.
165