1*4882a593Smuzhiyun.. _magicnumbers: 2*4882a593Smuzhiyun 3*4882a593SmuzhiyunLinux magic numbers 4*4882a593Smuzhiyun=================== 5*4882a593Smuzhiyun 6*4882a593SmuzhiyunThis file is a registry of magic numbers which are in use. When you 7*4882a593Smuzhiyunadd a magic number to a structure, you should also add it to this 8*4882a593Smuzhiyunfile, since it is best if the magic numbers used by various structures 9*4882a593Smuzhiyunare unique. 10*4882a593Smuzhiyun 11*4882a593SmuzhiyunIt is a **very** good idea to protect kernel data structures with magic 12*4882a593Smuzhiyunnumbers. This allows you to check at run time whether (a) a structure 13*4882a593Smuzhiyunhas been clobbered, or (b) you've passed the wrong structure to a 14*4882a593Smuzhiyunroutine. This last is especially useful --- particularly when you are 15*4882a593Smuzhiyunpassing pointers to structures via a void * pointer. The tty code, 16*4882a593Smuzhiyunfor example, does this frequently to pass driver-specific and line 17*4882a593Smuzhiyundiscipline-specific structures back and forth. 18*4882a593Smuzhiyun 19*4882a593SmuzhiyunThe way to use magic numbers is to declare them at the beginning of 20*4882a593Smuzhiyunthe structure, like so:: 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun struct tty_ldisc { 23*4882a593Smuzhiyun int magic; 24*4882a593Smuzhiyun ... 25*4882a593Smuzhiyun }; 26*4882a593Smuzhiyun 27*4882a593SmuzhiyunPlease follow this discipline when you are adding future enhancements 28*4882a593Smuzhiyunto the kernel! It has saved me countless hours of debugging, 29*4882a593Smuzhiyunespecially in the screwy cases where an array has been overrun and 30*4882a593Smuzhiyunstructures following the array have been overwritten. Using this 31*4882a593Smuzhiyundiscipline, these cases get detected quickly and safely. 32*4882a593Smuzhiyun 33*4882a593SmuzhiyunChangelog:: 34*4882a593Smuzhiyun 35*4882a593Smuzhiyun Theodore Ts'o 36*4882a593Smuzhiyun 31 Mar 94 37*4882a593Smuzhiyun 38*4882a593Smuzhiyun The magic table is current to Linux 2.1.55. 39*4882a593Smuzhiyun 40*4882a593Smuzhiyun Michael Chastain 41*4882a593Smuzhiyun <mailto:mec@shout.net> 42*4882a593Smuzhiyun 22 Sep 1997 43*4882a593Smuzhiyun 44*4882a593Smuzhiyun Now it should be up to date with Linux 2.1.112. Because 45*4882a593Smuzhiyun we are in feature freeze time it is very unlikely that 46*4882a593Smuzhiyun something will change before 2.2.x. The entries are 47*4882a593Smuzhiyun sorted by number field. 48*4882a593Smuzhiyun 49*4882a593Smuzhiyun Krzysztof G. Baranowski 50*4882a593Smuzhiyun <mailto: kgb@knm.org.pl> 51*4882a593Smuzhiyun 29 Jul 1998 52*4882a593Smuzhiyun 53*4882a593Smuzhiyun Updated the magic table to Linux 2.5.45. Right over the feature freeze, 54*4882a593Smuzhiyun but it is possible that some new magic numbers will sneak into the 55*4882a593Smuzhiyun kernel before 2.6.x yet. 56*4882a593Smuzhiyun 57*4882a593Smuzhiyun Petr Baudis 58*4882a593Smuzhiyun <pasky@ucw.cz> 59*4882a593Smuzhiyun 03 Nov 2002 60*4882a593Smuzhiyun 61*4882a593Smuzhiyun Updated the magic table to Linux 2.5.74. 62*4882a593Smuzhiyun 63*4882a593Smuzhiyun Fabian Frederick 64*4882a593Smuzhiyun <ffrederick@users.sourceforge.net> 65*4882a593Smuzhiyun 09 Jul 2003 66*4882a593Smuzhiyun 67*4882a593Smuzhiyun 68*4882a593Smuzhiyun===================== ================ ======================== ========================================== 69*4882a593SmuzhiyunMagic Name Number Structure File 70*4882a593Smuzhiyun===================== ================ ======================== ========================================== 71*4882a593SmuzhiyunPG_MAGIC 'P' pg_{read,write}_hdr ``include/linux/pg.h`` 72*4882a593SmuzhiyunCMAGIC 0x0111 user ``include/linux/a.out.h`` 73*4882a593SmuzhiyunMKISS_DRIVER_MAGIC 0x04bf mkiss_channel ``drivers/net/mkiss.h`` 74*4882a593SmuzhiyunHDLC_MAGIC 0x239e n_hdlc ``drivers/char/n_hdlc.c`` 75*4882a593SmuzhiyunAPM_BIOS_MAGIC 0x4101 apm_user ``arch/x86/kernel/apm_32.c`` 76*4882a593SmuzhiyunCYCLADES_MAGIC 0x4359 cyclades_port ``include/linux/cyclades.h`` 77*4882a593SmuzhiyunDB_MAGIC 0x4442 fc_info ``drivers/net/iph5526_novram.c`` 78*4882a593SmuzhiyunDL_MAGIC 0x444d fc_info ``drivers/net/iph5526_novram.c`` 79*4882a593SmuzhiyunFASYNC_MAGIC 0x4601 fasync_struct ``include/linux/fs.h`` 80*4882a593SmuzhiyunFF_MAGIC 0x4646 fc_info ``drivers/net/iph5526_novram.c`` 81*4882a593SmuzhiyunISICOM_MAGIC 0x4d54 isi_port ``include/linux/isicom.h`` 82*4882a593SmuzhiyunPTY_MAGIC 0x5001 ``drivers/char/pty.c`` 83*4882a593SmuzhiyunPPP_MAGIC 0x5002 ppp ``include/linux/if_pppvar.h`` 84*4882a593SmuzhiyunSSTATE_MAGIC 0x5302 serial_state ``include/linux/serial.h`` 85*4882a593SmuzhiyunSLIP_MAGIC 0x5302 slip ``drivers/net/slip.h`` 86*4882a593SmuzhiyunSTRIP_MAGIC 0x5303 strip ``drivers/net/strip.c`` 87*4882a593SmuzhiyunX25_ASY_MAGIC 0x5303 x25_asy ``drivers/net/x25_asy.h`` 88*4882a593SmuzhiyunSIXPACK_MAGIC 0x5304 sixpack ``drivers/net/hamradio/6pack.h`` 89*4882a593SmuzhiyunAX25_MAGIC 0x5316 ax_disp ``drivers/net/mkiss.h`` 90*4882a593SmuzhiyunTTY_MAGIC 0x5401 tty_struct ``include/linux/tty.h`` 91*4882a593SmuzhiyunMGSL_MAGIC 0x5401 mgsl_info ``drivers/char/synclink.c`` 92*4882a593SmuzhiyunTTY_DRIVER_MAGIC 0x5402 tty_driver ``include/linux/tty_driver.h`` 93*4882a593SmuzhiyunMGSLPC_MAGIC 0x5402 mgslpc_info ``drivers/char/pcmcia/synclink_cs.c`` 94*4882a593SmuzhiyunTTY_LDISC_MAGIC 0x5403 tty_ldisc ``include/linux/tty_ldisc.h`` 95*4882a593SmuzhiyunUSB_SERIAL_MAGIC 0x6702 usb_serial ``drivers/usb/serial/usb-serial.h`` 96*4882a593SmuzhiyunFULL_DUPLEX_MAGIC 0x6969 ``drivers/net/ethernet/dec/tulip/de2104x.c`` 97*4882a593SmuzhiyunUSB_BLUETOOTH_MAGIC 0x6d02 usb_bluetooth ``drivers/usb/class/bluetty.c`` 98*4882a593SmuzhiyunRFCOMM_TTY_MAGIC 0x6d02 ``net/bluetooth/rfcomm/tty.c`` 99*4882a593SmuzhiyunUSB_SERIAL_PORT_MAGIC 0x7301 usb_serial_port ``drivers/usb/serial/usb-serial.h`` 100*4882a593SmuzhiyunCG_MAGIC 0x00090255 ufs_cylinder_group ``include/linux/ufs_fs.h`` 101*4882a593SmuzhiyunRPORT_MAGIC 0x00525001 r_port ``drivers/char/rocket_int.h`` 102*4882a593SmuzhiyunLSEMAGIC 0x05091998 lse ``drivers/fc4/fc.c`` 103*4882a593SmuzhiyunGDTIOCTL_MAGIC 0x06030f07 gdth_iowr_str ``drivers/scsi/gdth_ioctl.h`` 104*4882a593SmuzhiyunRIEBL_MAGIC 0x09051990 ``drivers/net/atarilance.c`` 105*4882a593SmuzhiyunNBD_REQUEST_MAGIC 0x12560953 nbd_request ``include/linux/nbd.h`` 106*4882a593SmuzhiyunRED_MAGIC2 0x170fc2a5 (any) ``mm/slab.c`` 107*4882a593SmuzhiyunBAYCOM_MAGIC 0x19730510 baycom_state ``drivers/net/baycom_epp.c`` 108*4882a593SmuzhiyunISDN_X25IFACE_MAGIC 0x1e75a2b9 isdn_x25iface_proto_data ``drivers/isdn/isdn_x25iface.h`` 109*4882a593SmuzhiyunECP_MAGIC 0x21504345 cdkecpsig ``include/linux/cdk.h`` 110*4882a593SmuzhiyunLSOMAGIC 0x27091997 lso ``drivers/fc4/fc.c`` 111*4882a593SmuzhiyunLSMAGIC 0x2a3b4d2a ls ``drivers/fc4/fc.c`` 112*4882a593SmuzhiyunWANPIPE_MAGIC 0x414C4453 sdla_{dump,exec} ``include/linux/wanpipe.h`` 113*4882a593SmuzhiyunCS_CARD_MAGIC 0x43525553 cs_card ``sound/oss/cs46xx.c`` 114*4882a593SmuzhiyunLABELCL_MAGIC 0x4857434c labelcl_info_s ``include/asm/ia64/sn/labelcl.h`` 115*4882a593SmuzhiyunISDN_ASYNC_MAGIC 0x49344C01 modem_info ``include/linux/isdn.h`` 116*4882a593SmuzhiyunCTC_ASYNC_MAGIC 0x49344C01 ctc_tty_info ``drivers/s390/net/ctctty.c`` 117*4882a593SmuzhiyunISDN_NET_MAGIC 0x49344C02 isdn_net_local_s ``drivers/isdn/i4l/isdn_net_lib.h`` 118*4882a593SmuzhiyunSAVEKMSG_MAGIC2 0x4B4D5347 savekmsg ``arch/*/amiga/config.c`` 119*4882a593SmuzhiyunCS_STATE_MAGIC 0x4c4f4749 cs_state ``sound/oss/cs46xx.c`` 120*4882a593SmuzhiyunSLAB_C_MAGIC 0x4f17a36d kmem_cache ``mm/slab.c`` 121*4882a593SmuzhiyunCOW_MAGIC 0x4f4f4f4d cow_header_v1 ``arch/um/drivers/ubd_user.c`` 122*4882a593SmuzhiyunI810_CARD_MAGIC 0x5072696E i810_card ``sound/oss/i810_audio.c`` 123*4882a593SmuzhiyunTRIDENT_CARD_MAGIC 0x5072696E trident_card ``sound/oss/trident.c`` 124*4882a593SmuzhiyunROUTER_MAGIC 0x524d4157 wan_device [in ``wanrouter.h`` pre 3.9] 125*4882a593SmuzhiyunSAVEKMSG_MAGIC1 0x53415645 savekmsg ``arch/*/amiga/config.c`` 126*4882a593SmuzhiyunGDA_MAGIC 0x58464552 gda ``arch/mips/include/asm/sn/gda.h`` 127*4882a593SmuzhiyunRED_MAGIC1 0x5a2cf071 (any) ``mm/slab.c`` 128*4882a593SmuzhiyunEEPROM_MAGIC_VALUE 0x5ab478d2 lanai_dev ``drivers/atm/lanai.c`` 129*4882a593SmuzhiyunHDLCDRV_MAGIC 0x5ac6e778 hdlcdrv_state ``include/linux/hdlcdrv.h`` 130*4882a593SmuzhiyunPCXX_MAGIC 0x5c6df104 channel ``drivers/char/pcxx.h`` 131*4882a593SmuzhiyunKV_MAGIC 0x5f4b565f kernel_vars_s ``arch/mips/include/asm/sn/klkernvars.h`` 132*4882a593SmuzhiyunI810_STATE_MAGIC 0x63657373 i810_state ``sound/oss/i810_audio.c`` 133*4882a593SmuzhiyunTRIDENT_STATE_MAGIC 0x63657373 trient_state ``sound/oss/trident.c`` 134*4882a593SmuzhiyunM3_CARD_MAGIC 0x646e6f50 m3_card ``sound/oss/maestro3.c`` 135*4882a593SmuzhiyunFW_HEADER_MAGIC 0x65726F66 fw_header ``drivers/atm/fore200e.h`` 136*4882a593SmuzhiyunSLOT_MAGIC 0x67267321 slot ``drivers/hotplug/cpqphp.h`` 137*4882a593SmuzhiyunSLOT_MAGIC 0x67267322 slot ``drivers/hotplug/acpiphp.h`` 138*4882a593SmuzhiyunLO_MAGIC 0x68797548 nbd_device ``include/linux/nbd.h`` 139*4882a593SmuzhiyunOPROFILE_MAGIC 0x6f70726f super_block ``drivers/oprofile/oprofilefs.h`` 140*4882a593SmuzhiyunM3_STATE_MAGIC 0x734d724d m3_state ``sound/oss/maestro3.c`` 141*4882a593SmuzhiyunVMALLOC_MAGIC 0x87654320 snd_alloc_track ``sound/core/memory.c`` 142*4882a593SmuzhiyunKMALLOC_MAGIC 0x87654321 snd_alloc_track ``sound/core/memory.c`` 143*4882a593SmuzhiyunPWC_MAGIC 0x89DC10AB pwc_device ``drivers/usb/media/pwc.h`` 144*4882a593SmuzhiyunNBD_REPLY_MAGIC 0x96744668 nbd_reply ``include/linux/nbd.h`` 145*4882a593SmuzhiyunENI155_MAGIC 0xa54b872d midway_eprom ``drivers/atm/eni.h`` 146*4882a593SmuzhiyunCODA_MAGIC 0xC0DAC0DA coda_file_info ``fs/coda/coda_fs_i.h`` 147*4882a593SmuzhiyunDPMEM_MAGIC 0xc0ffee11 gdt_pci_sram ``drivers/scsi/gdth.h`` 148*4882a593SmuzhiyunYAM_MAGIC 0xF10A7654 yam_port ``drivers/net/hamradio/yam.c`` 149*4882a593SmuzhiyunCCB_MAGIC 0xf2691ad2 ccb ``drivers/scsi/ncr53c8xx.c`` 150*4882a593SmuzhiyunQUEUE_MAGIC_FREE 0xf7e1c9a3 queue_entry ``drivers/scsi/arm/queue.c`` 151*4882a593SmuzhiyunQUEUE_MAGIC_USED 0xf7e1cc33 queue_entry ``drivers/scsi/arm/queue.c`` 152*4882a593SmuzhiyunHTB_CMAGIC 0xFEFAFEF1 htb_class ``net/sched/sch_htb.c`` 153*4882a593SmuzhiyunNMI_MAGIC 0x48414d4d455201 nmi_s ``arch/mips/include/asm/sn/nmi.h`` 154*4882a593Smuzhiyun===================== ================ ======================== ========================================== 155*4882a593Smuzhiyun 156*4882a593SmuzhiyunNote that there are also defined special per-driver magic numbers in sound 157*4882a593Smuzhiyunmemory management. See ``include/sound/sndmagic.h`` for complete list of them. Many 158*4882a593SmuzhiyunOSS sound drivers have their magic numbers constructed from the soundcard PCI 159*4882a593SmuzhiyunID - these are not listed here as well. 160*4882a593Smuzhiyun 161*4882a593SmuzhiyunHFS is another larger user of magic numbers - you can find them in 162*4882a593Smuzhiyun``fs/hfs/hfs.h``. 163