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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
<mailto:mec@shout.net>
22 Sep 1997
Magic Name Number Structure File
===========================================================================
MKISS_DRIVER_MAGIC 0x04bf mkiss_channel drivers/net/mkiss.h
RISCOM8_MAGIC 0x0907 riscom_port drivers/char/riscom8.h
APM_BIOS_MAGIC 0x4101 apm_bios_struct include/linux/apm_bios.h
CYCLADES_MAGIC 0x4359 cyclades_port include/linux/cyclades.h
FASYNC_MAGIC 0x4601 fasync_struct include/linux/fs.h
PPP_MAGIC 0x5002 ppp include/linux/if_ppp.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
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
TTY_DRIVER_MAGIC 0x5402 tty_driver include/linux/tty_driver.h
TTY_LDISC_MAGIC 0x5403 tty_ldisc include/linux/tty_ldisc.h
SCC_MAGIC 0x8530 scc_channel include/linux/scc.h
RPORT_MAGIC 0x525001 r_port drivers/char/rocket_int.h
SLAB_C_MAGIC 0x4f17a36d kmem_cache_s mm/slab.c
SLAB_RED_MAGIC2 0x170fc2a5 (any) mm/slab.c
ECP_MAGIC 0x21504345 cdkecpsig include/linux/cdk.h
ISDN_ASYNC_MAGIC 0x49344C01 modem_info include/linux/isdn.h
ISDN_NET_MAGIC 0x49344C02 isdn_net_local_s include/linux/isdn.h
STLI_BOARDMAGIC 0x4bc6c825 stlibrd include/linux/istallion.h
ROUTER_MAGIC 0x524d4157 wan_device include/linux/wanrouter.h
SLAB_RED_MAGIC1 0x5a2cf071 (any) mm/slab.c
STL_PORTMAGIC 0x5a7182c9 stlport include/linux/stallion.h
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
STL_PANELMAGIC 0x7ef621a1 stlpanel include/linux/stallion.h
STL_BOARDMAGIC 0xa2267f52 stlbrd include/linux/stallion.h
SLAB_MAGIC_ALLOC 0xa5c32f2b kmem_slab_s mm/slab.c
SLAB_MAGIC_DESTROYED 0xb2f23c5a kmem_slab_s mm/slab.c
STLI_PORTMAGIC 0xe671c7a1 stliport include/linux/istallion.h
CCB_MAGIC 0xf2691ad2 ccb drivers/scsi/ncr53c8xx.c
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