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This file is a registry of magic numbers which are in use. When you
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add a magic number to a structure, you should also add it to this
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file, since it is best if the magic numbers used by various structures
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are unique.
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It is a *very* good idea to protect kernel data structures with magic
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numbers. This allows you to check at run time whether (a) a structure
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has been clobbered, or (b) you've passed the wrong structure to a
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routine. This last is especially useful --- particularly when you are
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passing pointers to structures via a void * pointer. The tty code,
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for example, does this frequently to pass driver-specific and line
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discipline-specific structures back and forth.
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The way to use magic numbers is to declare then at the beginning of
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the structure, like so:
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struct tty_ldisc {
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int magic;
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...
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};
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Please follow this discipline when you are adding future enhancements
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to the kernel! It has saved me countless hours of debugging,
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especially in the screwy cases where an array has been overrun and
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structures following the array have been overwritten. Using this
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discipline, these cases get detected quickly and safely.
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Theodore Ts'o
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31-Mar-94
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The magic table is current to Linux 1.3.98.
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Michael Chastain
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6 May 1996
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Magic Name Number Structure File
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===========================================================================
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RISCOM8_MAGIC 0x0907 struct riscom_port drivers/char/riscom8.h
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APM_BIOS_MAGIC 0x4101 struct apm_struct include/linux/apm_bios.h
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CYCLADES_MAGIC 0x4359 struct cyclades_port include/linux/cyclades.h
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FASYNC_MAGIC 0x4601 struct fasync_struct include/linux/fs.h
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PTY_MAGIC 0x5001 struct pty_struct drivers/char/pty.c
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PPP_MAGIC 0x5002 struct ppp_struct include/linux/if_ppp.h
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SERIAL_MAGIC 0x5301 struct async_struct include/linux/serial.h
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SLIP_MAGIC 0x5302 struct slip drivers/net/slip.h
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STRIP_MAGIC 0x5303 struct strip drivers/net/strip.c
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TTY_MAGIC 0x5401 struct tty_struct include/linux/tty.h
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TTY_DRIVER_MAGIC 0x5402 struct tty_driver include/linux/tty_driver.h
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TTY_LDISC_MAGIC 0x5403 struct tty_ldisc include/linux/tty_ldisc.h
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SCC_MAGIC 0x8530 struct scc_channel include/linux/scc.h
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ISDN_ASYNC_MAGIC 0x49344C01 modem_info include/linux/isdn.h
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ISDN_NET_MAGIC 0x49344C02 isdn_net_ndev include/linux/isdn.h
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STLI_BOARDMAGIC 0x4bc6c825 stlibrd_t include/linux/istallion.h
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STLI_PORTMAGIC 0xe671c7a1 stliport_t include/linux/istallion.h
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STL_PANELMAGIC 0x7ef621a1 stlpanel_t include/linux/stallion.h
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STL_BOARDMAGIC 0xa2267f52 stlbrd_t include/linux/stallion.h
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STL_PORTMAGIC 0x5a7182c9 stlport_t include/linux/stallion.h
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PCXX_MAGIC 0x5c6df104 struct channel drivers/char/pcxx.h
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BAYCOM_MAGIC 0x3105bac0 struct baycom_state drivers/char/baycom.c
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