1.\" $OpenBSD: ksyms.4,v 1.13 2013/11/01 12:08:51 fgsch Exp $ 2.\" 3.\" Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com> 4.\" 5.\" Permission to use, copy, modify, and distribute this software for any 6.\" purpose with or without fee is hereby granted, provided that the above 7.\" copyright notice and this permission notice appear in all copies. 8.\" 9.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16.\" 17.Dd $Mdocdate: November 1 2013 $ 18.Dt KSYMS 4 19.Os 20.Sh NAME 21.Nm ksyms 22.Nd kernel symbol table device 23.Sh SYNOPSIS 24.Cd "pseudo-device ksyms" Op Ar count 25.Sh DESCRIPTION 26The 27.Pa /dev/ksyms 28device masquerades as an 29.Ox 30native executable with the symbols from the running kernel as its symbol segment. 31Use of 32.Pa /dev/ksyms 33requires that the boot loader preserve the kernel symbols and place 34them at the end of the kernel's address space. 35.Pp 36The 37.Pa /dev/ksyms 38device is used to look up the symbol table name list from the running 39kernel. 40Because it represents the running kernel it is guaranteed 41to always be up to date even if the kernel file has been changed (or 42is even non-existent). 43It is most useful when used in conjunction with 44.Xr nlist 3 45or the 46.Xr kvm 3 47routines (note that 48.Xr kvm_open 3 49and 50.Xr kvm_openfiles 3 51will try 52.Pa /dev/ksyms 53automatically if the first parameter to them is the 54.Dv NULL 55pointer). 56.Sh FILES 57.Bl -tag -width Pa -compact 58.It Pa /dev/ksyms 59.El 60.Sh ERRORS 61An open of 62.Pa /dev/ksyms 63will fail if: 64.Bl -tag -width Er 65.It Bq Er EPERM 66An open was attempted with write permissions. 67.It Bq Er ENXIO 68No kernel symbols were saved by the boot loader (usually because 69they were removed with 70.Xr strip 1 ) , 71or the kernel has been compiled without a 72.Dq pseudo-device ksyms 73line. 74.El 75.Sh SEE ALSO 76.Xr kvm 3 , 77.Xr nlist 3 78.Sh HISTORY 79The 80.Pa /dev/ksyms 81device appeared in 82.Ox 2.4 . 83.Sh BUGS 84It is not possible to 85.Xr mmap 2 86.Pa /dev/ksyms 87because the boot loader does not load the symbol table onto a page 88boundary (so it is not page aligned). 89If all the boot loaders were fixed, 90.Xr mmap 2 91support would be trivial. 92