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UBUNTU: Ubuntu-raspi2-4.10.0-1019.22
[mirror_ubuntu-zesty-kernel.git] / Documentation / process / magic-number.rst
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9a11e153
MCC		 1Linux magic numbers
2===================
3
1da177e4
LT		 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
9a11e153 9It is a **very** good idea to protect kernel data structures with magic
1da177e4
LT		 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
9a11e153 18the structure, like so::
1da177e4 19
9a11e153
MCC		 20 struct tty_ldisc {
21 int magic;
22 ...
23 };
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LT		 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
9a11e153
MCC		 31Changelog::
32
1da177e4
LT		 33 Theodore Ts'o
34 31 Mar 94
35
9a11e153 36 The magic table is current to Linux 2.1.55.
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LT		 37
38 Michael Chastain
39 <mailto:mec@shout.net>
40 22 Sep 1997
41
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MCC		 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.
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LT		 46
47 Krzysztof G. Baranowski
48 <mailto: kgb@knm.org.pl>
49 29 Jul 1998
50
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MCC		 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.
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LT		 54
55 Petr Baudis
56 <pasky@ucw.cz>
57 03 Nov 2002
58
9a11e153 59 Updated the magic table to Linux 2.5.74.
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LT		 60
61 Fabian Frederick
62 <ffrederick@users.sourceforge.net>
63 09 Jul 2003
64
65
9a11e153
MCC		 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===================== ================ ======================== ==========================================
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LT		 154
155Note that there are also defined special per-driver magic numbers in sound
9a11e153 156memory management. See ``include/sound/sndmagic.h`` for complete list of them. Many
1da177e4
LT		 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
9a11e153 161``include/net/irda/irda.h`` for a complete list of them.
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LT		 162
163HFS is another larger user of magic numbers - you can find them in
9a11e153 164``fs/hfs/hfs.h``.
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