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head/share/man/man4/ksyms.4

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	.\" SUCH DAMAGE.			.\" SUCH DAMAGE.
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	.\" $FreeBSD$			.\" $FreeBSD$
	.\"			.\"
	.Dd April 5, 2009			.Dd August 2, 2017
	.Dt KSYMS 4			.Dt KSYMS 4
	.Os			.Os
	.Sh NAME			.Sh NAME
	.Nm ksyms			.Nm ksyms
	.Nd kernel symbol table interface			.Nd kernel symbol table interface
	.Sh SYNOPSIS			.Sh SYNOPSIS
	.Cd "device ksyms"			.Cd "device ksyms"
	.Sh DESCRIPTION			.Sh DESCRIPTION
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	.Pa /dev/ksyms			.Pa /dev/ksyms
	has no text or data, most of the fields are initialized to NULL.			has no text or data, most of the fields are initialized to NULL.
	The			The
	.Nm			.Nm
	driver does not block the loading or unloading of modules into the kernel			driver does not block the loading or unloading of modules into the kernel
	while the			while the
	.Pa /dev/ksyms			.Pa /dev/ksyms
	file is open but may contain stale data.			file is open but may contain stale data.
	.Sh IOCTLS
	The
	.Xr ioctl 2
	command codes below are defined in
	.Aq Pa sys/ksyms.h .
	.Pp
	The (third) argument to the
	.Xr ioctl 2
	should be a pointer to the type indicated.
	.Bl -tag -width indent -offset indent
	.It Dv KIOCGSIZE (size_t)
	Returns the total size of the current symbol table.
	This can be used when allocating a buffer to make a copy of
	the kernel symbol table.
	.It Dv KIOCGADDR (void *)
	Returns the address of the kernel symbol table mapped in
	the process memory.
	.El
	.Sh FILES			.Sh FILES
	.Bl -tag -width /dev/ksymsX			.Bl -tag -width /dev/ksymsX
	.It Pa /dev/ksyms			.It Pa /dev/ksyms
	.El			.El
	.Sh ERRORS			.Sh ERRORS
	An			An
	.Xr open 2			.Xr open 2
	of			of
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	There is a resource shortage in the kernel.			There is a resource shortage in the kernel.
	.It Bq Er ENXIO			.It Bq Er ENXIO
	The driver was unsuccessful in creating a snapshot of the kernel symbol			The driver was unsuccessful in creating a snapshot of the kernel symbol
	table.			table.
	This may occur if the kernel was in the process of loading or			This may occur if the kernel was in the process of loading or
	unloading a module.			unloading a module.
	.El			.El
	.Sh SEE ALSO			.Sh SEE ALSO
	.Xr ioctl 2 ,
	.Xr nlist 3 ,			.Xr nlist 3 ,
	.Xr elf 5 ,			.Xr elf 5 ,
	.Xr kldload 8			.Xr kldload 8
	.Sh HISTORY			.Sh HISTORY
	A			A
	.Nm			.Nm
	device exists in many different operating systems.			device exists in many different operating systems.
	This implementation is similar in function to the Solaris and NetBSD			This implementation is similar in function to the Solaris and NetBSD
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	To get a new snapshot you must close and re-open the device.			To get a new snapshot you must close and re-open the device.
	.Pp			.Pp
	A process is only allowed to open the			A process is only allowed to open the
	.Pa /dev/ksyms			.Pa /dev/ksyms
	file once at a time.			file once at a time.
	The process must close the			The process must close the
	.Pa /dev/ksyms			.Pa /dev/ksyms
	before it is allowed to open it again.			before it is allowed to open it again.
	.Pp
	The
	.Nm
	driver uses the calling process' memory address space to store the snapshot.
	.Xr ioctl 2
	can be used to get the memory address where the symbol table is stored to
	save kernel memory.
	.Xr mmap 2
	may also be used but it will map it to another address.