0001 .. _magicnumbers:
0002
0003 Linux magic numbers
0004 ===================
0005
0006 This file is a registry of magic numbers which are in use. When you
0007 add a magic number to a structure, you should also add it to this
0008 file, since it is best if the magic numbers used by various structures
0009 are unique.
0010
0011 It is a **very** good idea to protect kernel data structures with magic
0012 numbers. This allows you to check at run time whether (a) a structure
0013 has been clobbered, or (b) you've passed the wrong structure to a
0014 routine. This last is especially useful --- particularly when you are
0015 passing pointers to structures via a void * pointer. The tty code,
0016 for example, does this frequently to pass driver-specific and line
0017 discipline-specific structures back and forth.
0018
0019 The way to use magic numbers is to declare them at the beginning of
0020 the structure, like so::
0021
0022 struct tty_ldisc {
0023 int magic;
0024 ...
0025 };
0026
0027 Please follow this discipline when you are adding future enhancements
0028 to the kernel! It has saved me countless hours of debugging,
0029 especially in the screwy cases where an array has been overrun and
0030 structures following the array have been overwritten. Using this
0031 discipline, these cases get detected quickly and safely.
0032
0033 Changelog::
0034
0035 Theodore Ts'o
0036 31 Mar 94
0037
0038 The magic table is current to Linux 2.1.55.
0039
0040 Michael Chastain
0041 <mailto:mec@shout.net>
0042 22 Sep 1997
0043
0044 Now it should be up to date with Linux 2.1.112. Because
0045 we are in feature freeze time it is very unlikely that
0046 something will change before 2.2.x. The entries are
0047 sorted by number field.
0048
0049 Krzysztof G. Baranowski
0050 <mailto: kgb@knm.org.pl>
0051 29 Jul 1998
0052
0053 Updated the magic table to Linux 2.5.45. Right over the feature freeze,
0054 but it is possible that some new magic numbers will sneak into the
0055 kernel before 2.6.x yet.
0056
0057 Petr Baudis
0058 <pasky@ucw.cz>
0059 03 Nov 2002
0060
0061 Updated the magic table to Linux 2.5.74.
0062
0063 Fabian Frederick
0064 <ffrederick@users.sourceforge.net>
0065 09 Jul 2003
0066
0067
0068 ===================== ================ ======================== ==========================================
0069 Magic Name Number Structure File
0070 ===================== ================ ======================== ==========================================
0071 PG_MAGIC 'P' pg_{read,write}_hdr ``include/linux/pg.h``
0072 CMAGIC 0x0111 user ``include/linux/a.out.h``
0073 MKISS_DRIVER_MAGIC 0x04bf mkiss_channel ``drivers/net/mkiss.h``
0074 HDLC_MAGIC 0x239e n_hdlc ``drivers/char/n_hdlc.c``
0075 APM_BIOS_MAGIC 0x4101 apm_user ``arch/x86/kernel/apm_32.c``
0076 DB_MAGIC 0x4442 fc_info ``drivers/net/iph5526_novram.c``
0077 DL_MAGIC 0x444d fc_info ``drivers/net/iph5526_novram.c``
0078 FASYNC_MAGIC 0x4601 fasync_struct ``include/linux/fs.h``
0079 FF_MAGIC 0x4646 fc_info ``drivers/net/iph5526_novram.c``
0080 PTY_MAGIC 0x5001 ``drivers/char/pty.c``
0081 PPP_MAGIC 0x5002 ppp ``include/linux/if_pppvar.h``
0082 SSTATE_MAGIC 0x5302 serial_state ``include/linux/serial.h``
0083 SLIP_MAGIC 0x5302 slip ``drivers/net/slip.h``
0084 STRIP_MAGIC 0x5303 strip ``drivers/net/strip.c``
0085 SIXPACK_MAGIC 0x5304 sixpack ``drivers/net/hamradio/6pack.h``
0086 AX25_MAGIC 0x5316 ax_disp ``drivers/net/mkiss.h``
0087 TTY_MAGIC 0x5401 tty_struct ``include/linux/tty.h``
0088 MGSL_MAGIC 0x5401 mgsl_info ``drivers/char/synclink.c``
0089 TTY_DRIVER_MAGIC 0x5402 tty_driver ``include/linux/tty_driver.h``
0090 MGSLPC_MAGIC 0x5402 mgslpc_info ``drivers/char/pcmcia/synclink_cs.c``
0091 USB_SERIAL_MAGIC 0x6702 usb_serial ``drivers/usb/serial/usb-serial.h``
0092 FULL_DUPLEX_MAGIC 0x6969 ``drivers/net/ethernet/dec/tulip/de2104x.c``
0093 USB_BLUETOOTH_MAGIC 0x6d02 usb_bluetooth ``drivers/usb/class/bluetty.c``
0094 RFCOMM_TTY_MAGIC 0x6d02 ``net/bluetooth/rfcomm/tty.c``
0095 USB_SERIAL_PORT_MAGIC 0x7301 usb_serial_port ``drivers/usb/serial/usb-serial.h``
0096 CG_MAGIC 0x00090255 ufs_cylinder_group ``include/linux/ufs_fs.h``
0097 LSEMAGIC 0x05091998 lse ``drivers/fc4/fc.c``
0098 RIEBL_MAGIC 0x09051990 ``drivers/net/atarilance.c``
0099 NBD_REQUEST_MAGIC 0x12560953 nbd_request ``include/linux/nbd.h``
0100 RED_MAGIC2 0x170fc2a5 (any) ``mm/slab.c``
0101 BAYCOM_MAGIC 0x19730510 baycom_state ``drivers/net/baycom_epp.c``
0102 ISDN_X25IFACE_MAGIC 0x1e75a2b9 isdn_x25iface_proto_data ``drivers/isdn/isdn_x25iface.h``
0103 ECP_MAGIC 0x21504345 cdkecpsig ``include/linux/cdk.h``
0104 LSOMAGIC 0x27091997 lso ``drivers/fc4/fc.c``
0105 LSMAGIC 0x2a3b4d2a ls ``drivers/fc4/fc.c``
0106 WANPIPE_MAGIC 0x414C4453 sdla_{dump,exec} ``include/linux/wanpipe.h``
0107 CS_CARD_MAGIC 0x43525553 cs_card ``sound/oss/cs46xx.c``
0108 LABELCL_MAGIC 0x4857434c labelcl_info_s ``include/asm/ia64/sn/labelcl.h``
0109 ISDN_ASYNC_MAGIC 0x49344C01 modem_info ``include/linux/isdn.h``
0110 CTC_ASYNC_MAGIC 0x49344C01 ctc_tty_info ``drivers/s390/net/ctctty.c``
0111 ISDN_NET_MAGIC 0x49344C02 isdn_net_local_s ``drivers/isdn/i4l/isdn_net_lib.h``
0112 SAVEKMSG_MAGIC2 0x4B4D5347 savekmsg ``arch/*/amiga/config.c``
0113 CS_STATE_MAGIC 0x4c4f4749 cs_state ``sound/oss/cs46xx.c``
0114 SLAB_C_MAGIC 0x4f17a36d kmem_cache ``mm/slab.c``
0115 COW_MAGIC 0x4f4f4f4d cow_header_v1 ``arch/um/drivers/ubd_user.c``
0116 I810_CARD_MAGIC 0x5072696E i810_card ``sound/oss/i810_audio.c``
0117 TRIDENT_CARD_MAGIC 0x5072696E trident_card ``sound/oss/trident.c``
0118 ROUTER_MAGIC 0x524d4157 wan_device [in ``wanrouter.h`` pre 3.9]
0119 SAVEKMSG_MAGIC1 0x53415645 savekmsg ``arch/*/amiga/config.c``
0120 GDA_MAGIC 0x58464552 gda ``arch/mips/include/asm/sn/gda.h``
0121 RED_MAGIC1 0x5a2cf071 (any) ``mm/slab.c``
0122 EEPROM_MAGIC_VALUE 0x5ab478d2 lanai_dev ``drivers/atm/lanai.c``
0123 HDLCDRV_MAGIC 0x5ac6e778 hdlcdrv_state ``include/linux/hdlcdrv.h``
0124 PCXX_MAGIC 0x5c6df104 channel ``drivers/char/pcxx.h``
0125 KV_MAGIC 0x5f4b565f kernel_vars_s ``arch/mips/include/asm/sn/klkernvars.h``
0126 I810_STATE_MAGIC 0x63657373 i810_state ``sound/oss/i810_audio.c``
0127 TRIDENT_STATE_MAGIC 0x63657373 trient_state ``sound/oss/trident.c``
0128 M3_CARD_MAGIC 0x646e6f50 m3_card ``sound/oss/maestro3.c``
0129 FW_HEADER_MAGIC 0x65726F66 fw_header ``drivers/atm/fore200e.h``
0130 SLOT_MAGIC 0x67267321 slot ``drivers/hotplug/cpqphp.h``
0131 SLOT_MAGIC 0x67267322 slot ``drivers/hotplug/acpiphp.h``
0132 LO_MAGIC 0x68797548 nbd_device ``include/linux/nbd.h``
0133 M3_STATE_MAGIC 0x734d724d m3_state ``sound/oss/maestro3.c``
0134 VMALLOC_MAGIC 0x87654320 snd_alloc_track ``sound/core/memory.c``
0135 KMALLOC_MAGIC 0x87654321 snd_alloc_track ``sound/core/memory.c``
0136 PWC_MAGIC 0x89DC10AB pwc_device ``drivers/usb/media/pwc.h``
0137 NBD_REPLY_MAGIC 0x96744668 nbd_reply ``include/linux/nbd.h``
0138 ENI155_MAGIC 0xa54b872d midway_eprom ``drivers/atm/eni.h``
0139 CODA_MAGIC 0xC0DAC0DA coda_file_info ``fs/coda/coda_fs_i.h``
0140 YAM_MAGIC 0xF10A7654 yam_port ``drivers/net/hamradio/yam.c``
0141 CCB_MAGIC 0xf2691ad2 ccb ``drivers/scsi/ncr53c8xx.c``
0142 QUEUE_MAGIC_FREE 0xf7e1c9a3 queue_entry ``drivers/scsi/arm/queue.c``
0143 QUEUE_MAGIC_USED 0xf7e1cc33 queue_entry ``drivers/scsi/arm/queue.c``
0144 HTB_CMAGIC 0xFEFAFEF1 htb_class ``net/sched/sch_htb.c``
0145 NMI_MAGIC 0x48414d4d455201 nmi_s ``arch/mips/include/asm/sn/nmi.h``
0146 ===================== ================ ======================== ==========================================
0147
0148 Note that there are also defined special per-driver magic numbers in sound
0149 memory management. See ``include/sound/sndmagic.h`` for complete list of them. Many
0150 OSS sound drivers have their magic numbers constructed from the soundcard PCI
0151 ID - these are not listed here as well.
0152
0153 HFS is another larger user of magic numbers - you can find them in
0154 ``fs/hfs/hfs.h``.
