.\" $NetBSD: crashme.9,v 1.5 2021/12/11 23:47:53 riastradh Exp $
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.\" Copyright (c) 2019 Matthew R. Green
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.Dd January 7, 2019
.Dt CRASHME 9
.Os
.Sh NAME
.Nm crashme ,
.Nm crashme_add ,
.Nm crashme_remove
.Nd in-kernel testing of crash handling
.Sh SYNOPSIS
.In sys/crashme.h
.Ft int
.Fn crashme_add "crashme_node *cn"
.Ft int
.Fn crashme_remove "crashme_node *cn"
.Sh DESCRIPTION
The
.Nm
functions provide access to dynamically add and remove crashme nodes.
These nodes are simply named callbacks that are expected to cause the
system to crash.
.Pp
The crashme functionality is only available in kernels with the
.Xr options 4
.Dv DEBUG
option set.
.Pp
Each crashme node is maintained in a
.Vt crashme_node
structure which has the following public members:
.Bd -literal
typedef int (*crashme_fn)(int);

typedef struct crashme_node {
	const char	*cn_name;
	const char	*cn_longname;
	crashme_fn	 cn_fn;
} crashme_node;
.Ed
.Pp
The
caller must fill in the
.Fa cn_name ,
.Fa cn_longname ,
and
.Fa cn_fn
members.
.Pp
The
.Ar flags
parameter is passed from sysctl.
The return value is 0 upon success or non zero for failure.
.Sh SYSCTL SUPPORT
The following
.Xr sysctl 8
variables are provided by the
.Nm
subsystem:
.Bl -tag -width Li
.It Li debug.crashme_enable
Must be set to 1 for any
.Nm
node to be executed.
.El
.Pp
The following
.Xr sysctl 8
nodes trigger crashes in different ways when written:
.Bl -tag -width ".Li debug.crashme.null_deref"
.It Li debug.crashme.panic
Call
.Xr panic 9 .
.It Li debug.crashme.null_deref
Dereference a null pointer.
.It Li debug.crashme.null_jump
Call a null function pointer, i.e., jump to the instruction address
zero.
.It Li debug.crashme.ddb
Enter
.Xr ddb 9
directly by calling
.Xr Debugger 9 .
Requires
.Xr options 4
.Dv DDB .
.El
.Sh SEE ALSO
.Xr options 4 ,
.Xr panic 9
.Sh HISTORY
The
.Nm
driver appeared in
.Nx 9.0 .
.Sh AUTHORS
.An Matthew R. Green