path: root/Documentation/magic-number.txt
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authorLinus Torvalds <>2005-04-16 15:20:36 -0700
committerLinus Torvalds <>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/magic-number.txt
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+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 then 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.
+ Theodore Ts'o
+ 31 Mar 94
+The magic table is current to Linux 2.1.55.
+ Michael Chastain
+ <>
+ 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:>
+ 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
+ <>
+ 03 Nov 2002
+Updated the magic table to Linux 2.5.74.
+ Fabian Frederick
+ <>
+ 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
+RISCOM8_MAGIC 0x0907 riscom_port drivers/char/riscom8.h
+SPECIALIX_MAGIC 0x0907 specialix_port drivers/char/specialix_io8.h
+AURORA_MAGIC 0x0A18 Aurora_port drivers/sbus/char/aurora.h
+HDLC_MAGIC 0x239e n_hdlc drivers/char/n_hdlc.c
+APM_BIOS_MAGIC 0x4101 apm_user arch/i386/kernel/apm.c
+CYCLADES_MAGIC 0x4359 cyclades_port include/linux/cyclades.h
+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
+ISICOM_MAGIC 0x4d54 isi_port include/linux/isicom.h
+PTY_MAGIC 0x5001 drivers/char/pty.c
+PPP_MAGIC 0x5002 ppp include/linux/if_pppvar.h
+SERIAL_MAGIC 0x5301 async_struct include/linux/serial.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
+X25_ASY_MAGIC 0x5303 x25_asy drivers/net/x25_asy.h
+SIXPACK_MAGIC 0x5304 sixpack drivers/net/hamradio/6pack.h
+AX25_MAGIC 0x5316 ax_disp drivers/net/mkiss.h
+ESP_MAGIC 0x53ee esp_struct drivers/char/esp.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
+TTY_LDISC_MAGIC 0x5403 tty_ldisc include/linux/tty_ldisc.h
+USB_SERIAL_MAGIC 0x6702 usb_serial drivers/usb/serial/usb-serial.h
+FULL_DUPLEX_MAGIC 0x6969 drivers/net/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
+A2232_MAGIC 0x000a2232 gs_port drivers/char/ser_a2232.h
+SOLARIS_SOCKET_MAGIC 0x000ADDED sol_socket_struct arch/sparc64/solaris/socksys.h
+RPORT_MAGIC 0x00525001 r_port drivers/char/rocket_int.h
+LSEMAGIC 0x05091998 lse drivers/fc4/fc.c
+GDTIOCTL_MAGIC 0x06030f07 gdth_iowr_str drivers/scsi/gdth_ioctl.h
+RIEBL_MAGIC 0x09051990 drivers/net/atarilance.c
+RIO_MAGIC 0x12345678 gs_port drivers/char/rio/rio_linux.c
+SX_MAGIC 0x12345678 gs_port drivers/char/sx.h
+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
+STLI_BOARDMAGIC 0x4bc6c825 stlibrd include/linux/istallion.h
+CS_STATE_MAGIC 0x4c4f4749 cs_state sound/oss/cs46xx.c
+SLAB_C_MAGIC 0x4f17a36d kmem_cache_s 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 include/linux/wanrouter.h
+SCC_MAGIC 0x52696368 gs_port drivers/char/scc.h
+SAVEKMSG_MAGIC1 0x53415645 savekmsg arch/*/amiga/config.c
+GDA_MAGIC 0x58464552 gda include/asm-mips64/sn/gda.h
+RED_MAGIC1 0x5a2cf071 (any) mm/slab.c
+STL_PORTMAGIC 0x5a7182c9 stlport include/linux/stallion.h
+EEPROM_MAGIC_VALUE 0X5ab478d2 lanai_dev drivers/atm/lanai.c
+HDLCDRV_MAGIC 0x5ac6e778 hdlcdrv_state include/linux/hdlcdrv.h
+EPCA_MAGIC 0x5c6df104 channel include/linux/epca.h
+PCXX_MAGIC 0x5c6df104 channel drivers/char/pcxx.h
+KV_MAGIC 0x5f4b565f kernel_vars_s include/asm-mips64/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
+OPROFILE_MAGIC 0x6f70726f super_block drivers/oprofile/oprofilefs.h
+M3_STATE_MAGIC 0x734d724d m3_state sound/oss/maestro3.c
+STL_PANELMAGIC 0x7ef621a1 stlpanel include/linux/stallion.h
+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
+STL_BOARDMAGIC 0xa2267f52 stlbrd include/linux/stallion.h
+ENI155_MAGIC 0xa54b872d midway_eprom drivers/atm/eni.h
+SCI_MAGIC 0xbabeface gs_port drivers/char/sh-sci.h
+CODA_MAGIC 0xC0DAC0DA coda_file_info include/linux/coda_fs_i.h
+DPMEM_MAGIC 0xc0ffee11 gdt_pci_sram drivers/scsi/gdth.h
+STLI_PORTMAGIC 0xe671c7a1 stliport include/linux/istallion.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 include/asm-mips64/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.
+IrDA subsystem also uses large number of own magic numbers, see
+include/net/irda/irda.h for a complete list of them.
+HFS is another larger user of magic numbers - you can find them in