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1 | .. _magicnumbers: |
2 | ||
9a11e153 MCC |
3 | Linux magic numbers |
4 | =================== | |
5 | ||
1da177e4 LT |
6 | This file is a registry of magic numbers which are in use. When you |
7 | add a magic number to a structure, you should also add it to this | |
8 | file, since it is best if the magic numbers used by various structures | |
9 | are unique. | |
10 | ||
9a11e153 | 11 | It is a **very** good idea to protect kernel data structures with magic |
1da177e4 LT |
12 | numbers. This allows you to check at run time whether (a) a structure |
13 | has been clobbered, or (b) you've passed the wrong structure to a | |
14 | routine. This last is especially useful --- particularly when you are | |
15 | passing pointers to structures via a void * pointer. The tty code, | |
16 | for example, does this frequently to pass driver-specific and line | |
17 | discipline-specific structures back and forth. | |
18 | ||
738947f0 | 19 | The way to use magic numbers is to declare them at the beginning of |
9a11e153 | 20 | the structure, like so:: |
1da177e4 | 21 | |
9a11e153 MCC |
22 | struct tty_ldisc { |
23 | int magic; | |
24 | ... | |
25 | }; | |
1da177e4 LT |
26 | |
27 | Please follow this discipline when you are adding future enhancements | |
28 | to the kernel! It has saved me countless hours of debugging, | |
29 | especially in the screwy cases where an array has been overrun and | |
30 | structures following the array have been overwritten. Using this | |
31 | discipline, these cases get detected quickly and safely. | |
32 | ||
9a11e153 MCC |
33 | Changelog:: |
34 | ||
1da177e4 LT |
35 | Theodore Ts'o |
36 | 31 Mar 94 | |
37 | ||
9a11e153 | 38 | The magic table is current to Linux 2.1.55. |
1da177e4 LT |
39 | |
40 | Michael Chastain | |
41 | <mailto:mec@shout.net> | |
42 | 22 Sep 1997 | |
43 | ||
9a11e153 MCC |
44 | Now it should be up to date with Linux 2.1.112. Because |
45 | we are in feature freeze time it is very unlikely that | |
46 | something will change before 2.2.x. The entries are | |
47 | sorted by number field. | |
1da177e4 LT |
48 | |
49 | Krzysztof G. Baranowski | |
50 | <mailto: kgb@knm.org.pl> | |
51 | 29 Jul 1998 | |
52 | ||
9a11e153 MCC |
53 | Updated the magic table to Linux 2.5.45. Right over the feature freeze, |
54 | but it is possible that some new magic numbers will sneak into the | |
55 | kernel before 2.6.x yet. | |
1da177e4 LT |
56 | |
57 | Petr Baudis | |
58 | <pasky@ucw.cz> | |
59 | 03 Nov 2002 | |
60 | ||
9a11e153 | 61 | Updated the magic table to Linux 2.5.74. |
1da177e4 LT |
62 | |
63 | Fabian Frederick | |
64 | <ffrederick@users.sourceforge.net> | |
65 | 09 Jul 2003 | |
66 | ||
67 | ||
9a11e153 MCC |
68 | ===================== ================ ======================== ========================================== |
69 | Magic Name Number Structure File | |
70 | ===================== ================ ======================== ========================================== | |
71 | PG_MAGIC 'P' pg_{read,write}_hdr ``include/linux/pg.h`` | |
72 | CMAGIC 0x0111 user ``include/linux/a.out.h`` | |
73 | MKISS_DRIVER_MAGIC 0x04bf mkiss_channel ``drivers/net/mkiss.h`` | |
74 | HDLC_MAGIC 0x239e n_hdlc ``drivers/char/n_hdlc.c`` | |
75 | APM_BIOS_MAGIC 0x4101 apm_user ``arch/x86/kernel/apm_32.c`` | |
76 | CYCLADES_MAGIC 0x4359 cyclades_port ``include/linux/cyclades.h`` | |
77 | DB_MAGIC 0x4442 fc_info ``drivers/net/iph5526_novram.c`` | |
78 | DL_MAGIC 0x444d fc_info ``drivers/net/iph5526_novram.c`` | |
79 | FASYNC_MAGIC 0x4601 fasync_struct ``include/linux/fs.h`` | |
80 | FF_MAGIC 0x4646 fc_info ``drivers/net/iph5526_novram.c`` | |
81 | ISICOM_MAGIC 0x4d54 isi_port ``include/linux/isicom.h`` | |
82 | PTY_MAGIC 0x5001 ``drivers/char/pty.c`` | |
83 | PPP_MAGIC 0x5002 ppp ``include/linux/if_pppvar.h`` | |
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84 | SSTATE_MAGIC 0x5302 serial_state ``include/linux/serial.h`` |
85 | SLIP_MAGIC 0x5302 slip ``drivers/net/slip.h`` | |
86 | STRIP_MAGIC 0x5303 strip ``drivers/net/strip.c`` | |
87 | X25_ASY_MAGIC 0x5303 x25_asy ``drivers/net/x25_asy.h`` | |
88 | SIXPACK_MAGIC 0x5304 sixpack ``drivers/net/hamradio/6pack.h`` | |
89 | AX25_MAGIC 0x5316 ax_disp ``drivers/net/mkiss.h`` | |
90 | TTY_MAGIC 0x5401 tty_struct ``include/linux/tty.h`` | |
91 | MGSL_MAGIC 0x5401 mgsl_info ``drivers/char/synclink.c`` | |
92 | TTY_DRIVER_MAGIC 0x5402 tty_driver ``include/linux/tty_driver.h`` | |
93 | MGSLPC_MAGIC 0x5402 mgslpc_info ``drivers/char/pcmcia/synclink_cs.c`` | |
94 | TTY_LDISC_MAGIC 0x5403 tty_ldisc ``include/linux/tty_ldisc.h`` | |
95 | USB_SERIAL_MAGIC 0x6702 usb_serial ``drivers/usb/serial/usb-serial.h`` | |
96 | FULL_DUPLEX_MAGIC 0x6969 ``drivers/net/ethernet/dec/tulip/de2104x.c`` | |
97 | USB_BLUETOOTH_MAGIC 0x6d02 usb_bluetooth ``drivers/usb/class/bluetty.c`` | |
98 | RFCOMM_TTY_MAGIC 0x6d02 ``net/bluetooth/rfcomm/tty.c`` | |
99 | USB_SERIAL_PORT_MAGIC 0x7301 usb_serial_port ``drivers/usb/serial/usb-serial.h`` | |
100 | CG_MAGIC 0x00090255 ufs_cylinder_group ``include/linux/ufs_fs.h`` | |
101 | RPORT_MAGIC 0x00525001 r_port ``drivers/char/rocket_int.h`` | |
102 | LSEMAGIC 0x05091998 lse ``drivers/fc4/fc.c`` | |
103 | GDTIOCTL_MAGIC 0x06030f07 gdth_iowr_str ``drivers/scsi/gdth_ioctl.h`` | |
104 | RIEBL_MAGIC 0x09051990 ``drivers/net/atarilance.c`` | |
105 | NBD_REQUEST_MAGIC 0x12560953 nbd_request ``include/linux/nbd.h`` | |
106 | RED_MAGIC2 0x170fc2a5 (any) ``mm/slab.c`` | |
107 | BAYCOM_MAGIC 0x19730510 baycom_state ``drivers/net/baycom_epp.c`` | |
108 | ISDN_X25IFACE_MAGIC 0x1e75a2b9 isdn_x25iface_proto_data ``drivers/isdn/isdn_x25iface.h`` | |
109 | ECP_MAGIC 0x21504345 cdkecpsig ``include/linux/cdk.h`` | |
110 | LSOMAGIC 0x27091997 lso ``drivers/fc4/fc.c`` | |
111 | LSMAGIC 0x2a3b4d2a ls ``drivers/fc4/fc.c`` | |
112 | WANPIPE_MAGIC 0x414C4453 sdla_{dump,exec} ``include/linux/wanpipe.h`` | |
113 | CS_CARD_MAGIC 0x43525553 cs_card ``sound/oss/cs46xx.c`` | |
114 | LABELCL_MAGIC 0x4857434c labelcl_info_s ``include/asm/ia64/sn/labelcl.h`` | |
115 | ISDN_ASYNC_MAGIC 0x49344C01 modem_info ``include/linux/isdn.h`` | |
116 | CTC_ASYNC_MAGIC 0x49344C01 ctc_tty_info ``drivers/s390/net/ctctty.c`` | |
117 | ISDN_NET_MAGIC 0x49344C02 isdn_net_local_s ``drivers/isdn/i4l/isdn_net_lib.h`` | |
118 | SAVEKMSG_MAGIC2 0x4B4D5347 savekmsg ``arch/*/amiga/config.c`` | |
119 | CS_STATE_MAGIC 0x4c4f4749 cs_state ``sound/oss/cs46xx.c`` | |
120 | SLAB_C_MAGIC 0x4f17a36d kmem_cache ``mm/slab.c`` | |
121 | COW_MAGIC 0x4f4f4f4d cow_header_v1 ``arch/um/drivers/ubd_user.c`` | |
122 | I810_CARD_MAGIC 0x5072696E i810_card ``sound/oss/i810_audio.c`` | |
123 | TRIDENT_CARD_MAGIC 0x5072696E trident_card ``sound/oss/trident.c`` | |
124 | ROUTER_MAGIC 0x524d4157 wan_device [in ``wanrouter.h`` pre 3.9] | |
125 | SAVEKMSG_MAGIC1 0x53415645 savekmsg ``arch/*/amiga/config.c`` | |
126 | GDA_MAGIC 0x58464552 gda ``arch/mips/include/asm/sn/gda.h`` | |
127 | RED_MAGIC1 0x5a2cf071 (any) ``mm/slab.c`` | |
128 | EEPROM_MAGIC_VALUE 0x5ab478d2 lanai_dev ``drivers/atm/lanai.c`` | |
129 | HDLCDRV_MAGIC 0x5ac6e778 hdlcdrv_state ``include/linux/hdlcdrv.h`` | |
130 | PCXX_MAGIC 0x5c6df104 channel ``drivers/char/pcxx.h`` | |
131 | KV_MAGIC 0x5f4b565f kernel_vars_s ``arch/mips/include/asm/sn/klkernvars.h`` | |
132 | I810_STATE_MAGIC 0x63657373 i810_state ``sound/oss/i810_audio.c`` | |
133 | TRIDENT_STATE_MAGIC 0x63657373 trient_state ``sound/oss/trident.c`` | |
134 | M3_CARD_MAGIC 0x646e6f50 m3_card ``sound/oss/maestro3.c`` | |
135 | FW_HEADER_MAGIC 0x65726F66 fw_header ``drivers/atm/fore200e.h`` | |
136 | SLOT_MAGIC 0x67267321 slot ``drivers/hotplug/cpqphp.h`` | |
137 | SLOT_MAGIC 0x67267322 slot ``drivers/hotplug/acpiphp.h`` | |
138 | LO_MAGIC 0x68797548 nbd_device ``include/linux/nbd.h`` | |
139 | OPROFILE_MAGIC 0x6f70726f super_block ``drivers/oprofile/oprofilefs.h`` | |
140 | M3_STATE_MAGIC 0x734d724d m3_state ``sound/oss/maestro3.c`` | |
141 | VMALLOC_MAGIC 0x87654320 snd_alloc_track ``sound/core/memory.c`` | |
142 | KMALLOC_MAGIC 0x87654321 snd_alloc_track ``sound/core/memory.c`` | |
143 | PWC_MAGIC 0x89DC10AB pwc_device ``drivers/usb/media/pwc.h`` | |
144 | NBD_REPLY_MAGIC 0x96744668 nbd_reply ``include/linux/nbd.h`` | |
145 | ENI155_MAGIC 0xa54b872d midway_eprom ``drivers/atm/eni.h`` | |
146 | CODA_MAGIC 0xC0DAC0DA coda_file_info ``fs/coda/coda_fs_i.h`` | |
147 | DPMEM_MAGIC 0xc0ffee11 gdt_pci_sram ``drivers/scsi/gdth.h`` | |
148 | YAM_MAGIC 0xF10A7654 yam_port ``drivers/net/hamradio/yam.c`` | |
149 | CCB_MAGIC 0xf2691ad2 ccb ``drivers/scsi/ncr53c8xx.c`` | |
150 | QUEUE_MAGIC_FREE 0xf7e1c9a3 queue_entry ``drivers/scsi/arm/queue.c`` | |
151 | QUEUE_MAGIC_USED 0xf7e1cc33 queue_entry ``drivers/scsi/arm/queue.c`` | |
152 | HTB_CMAGIC 0xFEFAFEF1 htb_class ``net/sched/sch_htb.c`` | |
153 | NMI_MAGIC 0x48414d4d455201 nmi_s ``arch/mips/include/asm/sn/nmi.h`` | |
154 | ===================== ================ ======================== ========================================== | |
1da177e4 LT |
155 | |
156 | Note that there are also defined special per-driver magic numbers in sound | |
9a11e153 | 157 | memory management. See ``include/sound/sndmagic.h`` for complete list of them. Many |
1da177e4 LT |
158 | OSS sound drivers have their magic numbers constructed from the soundcard PCI |
159 | ID - these are not listed here as well. | |
160 | ||
1da177e4 | 161 | HFS is another larger user of magic numbers - you can find them in |
9a11e153 | 162 | ``fs/hfs/hfs.h``. |