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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
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
HDLC_MAGIC 0x239e n_hdlc drivers/char/n_hdlc.c
APM_BIOS_MAGIC 0x4101 apm_user arch/x86/kernel/apm_32.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
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
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 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 arch/mips/include/asm/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 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
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 fs/coda/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 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.
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