| .. _magicnumbers: |
| |
| Linux magic numbers |
| =================== |
| |
| This file is a registry of magic numbers which are in use. When you |
| add a magic number to a structure, you should also add it to this |
| file, since it is best if the magic numbers used by various structures |
| are unique. |
| |
| It is a **very** good idea to protect kernel data structures with magic |
| numbers. This allows you to check at run time whether (a) a structure |
| has been clobbered, or (b) you've passed the wrong structure to a |
| routine. This last is especially useful --- particularly when you are |
| passing pointers to structures via a void * pointer. The tty code, |
| for example, does this frequently to pass driver-specific and line |
| discipline-specific structures back and forth. |
| |
| The way to use magic numbers is to declare them at the beginning of |
| the structure, like so:: |
| |
| struct tty_ldisc { |
| int magic; |
| ... |
| }; |
| |
| Please follow this discipline when you are adding future enhancements |
| to the kernel! It has saved me countless hours of debugging, |
| especially in the screwy cases where an array has been overrun and |
| structures following the array have been overwritten. Using this |
| discipline, these cases get detected quickly and safely. |
| |
| Changelog:: |
| |
| Theodore Ts'o |
| 31 Mar 94 |
| |
| The magic table is current to Linux 2.1.55. |
| |
| Michael Chastain |
| <mailto:mec@shout.net> |
| 22 Sep 1997 |
| |
| Now it should be up to date with Linux 2.1.112. Because |
| we are in feature freeze time it is very unlikely that |
| something will change before 2.2.x. The entries are |
| sorted by number field. |
| |
| Krzysztof G. Baranowski |
| <mailto: kgb@knm.org.pl> |
| 29 Jul 1998 |
| |
| Updated the magic table to Linux 2.5.45. Right over the feature freeze, |
| but it is possible that some new magic numbers will sneak into the |
| kernel before 2.6.x yet. |
| |
| Petr Baudis |
| <pasky@ucw.cz> |
| 03 Nov 2002 |
| |
| Updated the magic table to Linux 2.5.74. |
| |
| Fabian Frederick |
| <ffrederick@users.sourceforge.net> |
| 09 Jul 2003 |
| |
| |
| ===================== ================ ======================== ========================================== |
| Magic Name Number Structure File |
| ===================== ================ ======================== ========================================== |
| PG_MAGIC 'P' pg_{read,write}_hdr ``include/linux/pg.h`` |
| CMAGIC 0x0111 user ``include/linux/a.out.h`` |
| MKISS_DRIVER_MAGIC 0x04bf mkiss_channel ``drivers/net/mkiss.h`` |
| HDLC_MAGIC 0x239e n_hdlc ``drivers/char/n_hdlc.c`` |
| APM_BIOS_MAGIC 0x4101 apm_user ``arch/x86/kernel/apm_32.c`` |
| DB_MAGIC 0x4442 fc_info ``drivers/net/iph5526_novram.c`` |
| DL_MAGIC 0x444d fc_info ``drivers/net/iph5526_novram.c`` |
| FASYNC_MAGIC 0x4601 fasync_struct ``include/linux/fs.h`` |
| FF_MAGIC 0x4646 fc_info ``drivers/net/iph5526_novram.c`` |
| PTY_MAGIC 0x5001 ``drivers/char/pty.c`` |
| PPP_MAGIC 0x5002 ppp ``include/linux/if_pppvar.h`` |
| SSTATE_MAGIC 0x5302 serial_state ``include/linux/serial.h`` |
| SLIP_MAGIC 0x5302 slip ``drivers/net/slip.h`` |
| STRIP_MAGIC 0x5303 strip ``drivers/net/strip.c`` |
| SIXPACK_MAGIC 0x5304 sixpack ``drivers/net/hamradio/6pack.h`` |
| AX25_MAGIC 0x5316 ax_disp ``drivers/net/mkiss.h`` |
| TTY_MAGIC 0x5401 tty_struct ``include/linux/tty.h`` |
| MGSL_MAGIC 0x5401 mgsl_info ``drivers/char/synclink.c`` |
| TTY_DRIVER_MAGIC 0x5402 tty_driver ``include/linux/tty_driver.h`` |
| MGSLPC_MAGIC 0x5402 mgslpc_info ``drivers/char/pcmcia/synclink_cs.c`` |
| USB_SERIAL_MAGIC 0x6702 usb_serial ``drivers/usb/serial/usb-serial.h`` |
| FULL_DUPLEX_MAGIC 0x6969 ``drivers/net/ethernet/dec/tulip/de2104x.c`` |
| USB_BLUETOOTH_MAGIC 0x6d02 usb_bluetooth ``drivers/usb/class/bluetty.c`` |
| RFCOMM_TTY_MAGIC 0x6d02 ``net/bluetooth/rfcomm/tty.c`` |
| USB_SERIAL_PORT_MAGIC 0x7301 usb_serial_port ``drivers/usb/serial/usb-serial.h`` |
| CG_MAGIC 0x00090255 ufs_cylinder_group ``include/linux/ufs_fs.h`` |
| LSEMAGIC 0x05091998 lse ``drivers/fc4/fc.c`` |
| RIEBL_MAGIC 0x09051990 ``drivers/net/atarilance.c`` |
| NBD_REQUEST_MAGIC 0x12560953 nbd_request ``include/linux/nbd.h`` |
| RED_MAGIC2 0x170fc2a5 (any) ``mm/slab.c`` |
| BAYCOM_MAGIC 0x19730510 baycom_state ``drivers/net/baycom_epp.c`` |
| ISDN_X25IFACE_MAGIC 0x1e75a2b9 isdn_x25iface_proto_data ``drivers/isdn/isdn_x25iface.h`` |
| ECP_MAGIC 0x21504345 cdkecpsig ``include/linux/cdk.h`` |
| LSOMAGIC 0x27091997 lso ``drivers/fc4/fc.c`` |
| LSMAGIC 0x2a3b4d2a ls ``drivers/fc4/fc.c`` |
| WANPIPE_MAGIC 0x414C4453 sdla_{dump,exec} ``include/linux/wanpipe.h`` |
| CS_CARD_MAGIC 0x43525553 cs_card ``sound/oss/cs46xx.c`` |
| LABELCL_MAGIC 0x4857434c labelcl_info_s ``include/asm/ia64/sn/labelcl.h`` |
| ISDN_ASYNC_MAGIC 0x49344C01 modem_info ``include/linux/isdn.h`` |
| CTC_ASYNC_MAGIC 0x49344C01 ctc_tty_info ``drivers/s390/net/ctctty.c`` |
| ISDN_NET_MAGIC 0x49344C02 isdn_net_local_s ``drivers/isdn/i4l/isdn_net_lib.h`` |
| SAVEKMSG_MAGIC2 0x4B4D5347 savekmsg ``arch/*/amiga/config.c`` |
| CS_STATE_MAGIC 0x4c4f4749 cs_state ``sound/oss/cs46xx.c`` |
| SLAB_C_MAGIC 0x4f17a36d kmem_cache ``mm/slab.c`` |
| COW_MAGIC 0x4f4f4f4d cow_header_v1 ``arch/um/drivers/ubd_user.c`` |
| I810_CARD_MAGIC 0x5072696E i810_card ``sound/oss/i810_audio.c`` |
| TRIDENT_CARD_MAGIC 0x5072696E trident_card ``sound/oss/trident.c`` |
| ROUTER_MAGIC 0x524d4157 wan_device [in ``wanrouter.h`` pre 3.9] |
| SAVEKMSG_MAGIC1 0x53415645 savekmsg ``arch/*/amiga/config.c`` |
| GDA_MAGIC 0x58464552 gda ``arch/mips/include/asm/sn/gda.h`` |
| RED_MAGIC1 0x5a2cf071 (any) ``mm/slab.c`` |
| EEPROM_MAGIC_VALUE 0x5ab478d2 lanai_dev ``drivers/atm/lanai.c`` |
| HDLCDRV_MAGIC 0x5ac6e778 hdlcdrv_state ``include/linux/hdlcdrv.h`` |
| PCXX_MAGIC 0x5c6df104 channel ``drivers/char/pcxx.h`` |
| KV_MAGIC 0x5f4b565f kernel_vars_s ``arch/mips/include/asm/sn/klkernvars.h`` |
| I810_STATE_MAGIC 0x63657373 i810_state ``sound/oss/i810_audio.c`` |
| TRIDENT_STATE_MAGIC 0x63657373 trient_state ``sound/oss/trident.c`` |
| M3_CARD_MAGIC 0x646e6f50 m3_card ``sound/oss/maestro3.c`` |
| FW_HEADER_MAGIC 0x65726F66 fw_header ``drivers/atm/fore200e.h`` |
| SLOT_MAGIC 0x67267321 slot ``drivers/hotplug/cpqphp.h`` |
| SLOT_MAGIC 0x67267322 slot ``drivers/hotplug/acpiphp.h`` |
| LO_MAGIC 0x68797548 nbd_device ``include/linux/nbd.h`` |
| M3_STATE_MAGIC 0x734d724d m3_state ``sound/oss/maestro3.c`` |
| VMALLOC_MAGIC 0x87654320 snd_alloc_track ``sound/core/memory.c`` |
| KMALLOC_MAGIC 0x87654321 snd_alloc_track ``sound/core/memory.c`` |
| PWC_MAGIC 0x89DC10AB pwc_device ``drivers/usb/media/pwc.h`` |
| NBD_REPLY_MAGIC 0x96744668 nbd_reply ``include/linux/nbd.h`` |
| ENI155_MAGIC 0xa54b872d midway_eprom ``drivers/atm/eni.h`` |
| CODA_MAGIC 0xC0DAC0DA coda_file_info ``fs/coda/coda_fs_i.h`` |
| YAM_MAGIC 0xF10A7654 yam_port ``drivers/net/hamradio/yam.c`` |
| CCB_MAGIC 0xf2691ad2 ccb ``drivers/scsi/ncr53c8xx.c`` |
| QUEUE_MAGIC_FREE 0xf7e1c9a3 queue_entry ``drivers/scsi/arm/queue.c`` |
| QUEUE_MAGIC_USED 0xf7e1cc33 queue_entry ``drivers/scsi/arm/queue.c`` |
| HTB_CMAGIC 0xFEFAFEF1 htb_class ``net/sched/sch_htb.c`` |
| NMI_MAGIC 0x48414d4d455201 nmi_s ``arch/mips/include/asm/sn/nmi.h`` |
| ===================== ================ ======================== ========================================== |
| |
| Note that there are also defined special per-driver magic numbers in sound |
| memory management. See ``include/sound/sndmagic.h`` for complete list of them. Many |
| OSS sound drivers have their magic numbers constructed from the soundcard PCI |
| ID - these are not listed here as well. |
| |
| HFS is another larger user of magic numbers - you can find them in |
| ``fs/hfs/hfs.h``. |
