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.Dd November 12, 2008
.Dt KSYMS 4
.Os
.Sh NAME
.Nm ksyms
.Nd kernel symbol table interface
.Sh SYNOPSIS
.Cd "pseudo-device ksyms"
.Sh DESCRIPTION
The
.Pa /dev/ksyms
character device provides a read-only interface to the current
kernel symbol table.
It can be accessed either as a sequential
file, where it looks like an executable file but with zero-sized
text and data segments, or via
.Xr ioctl 2 .
.Pp
.Pa /dev/ksyms
represents the symbol table at the time when the device is opened,
and may not change until it is closed.
.Pp
The in-kernel symbol manager is designed to be able to handle
any type of symbol table.
However, only
.Xr elf 5
symbol tables are currently dealt with.
.Sh IOCTLS
The
.Xr ioctl 2
command codes below are defined in
.In 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 (int)
Returns the total size of the current symbol table.
This should be used when allocating a buffer to read in the
whole symbol table to memory.
.It Dv KIOCGVALUE (struct ksyms_gsymbol)
Returns the value for the given symbol name in a symtab-independent
fashion.
.Bd -literal -offset indent
struct ksyms_gsymbol {
	const char *kg_name;
	unsigned long *kg_value;
};
.Ed
.Pp
The struct element
.Va kg_name
should be set to the name of the requested value, and the address that
.Va kg_value
points to will receive the symbol value.
.It Dv KIOCGSYMBOL (struct ksyms_gsymbol)
Returns the complete symbol for the given symbol name.
.Bd -literal -offset indent
struct ksyms_gsymbol {
	const char *kg_name;
        void *kg_sym;
};
.Ed
.Pp
The struct element
.Va kg_name
should be set to the name of the requested symbol, and the found
symbol will be written to the
.Va kg_sym
address.
It is the callers responsibility to ensure that enough space
for the symbol is allocated.
.El
.Sh FILES
.Bl -tag -width /dev/ksymsX
.It Pa /dev/ksyms
.El
.Sh SEE ALSO
.Xr ioctl 2 ,
.Xr nlist 3 ,
.Xr elf 5
.Sh HISTORY
A
.Nm
device exists in many different operating systems.
This implementation is modelled in function after Solaris
.Nm .
This
.Nm
driver was written by Anders Magnusson for
.Nx .
.Pp
The
.Nm
driver first appeared in
.Nx 2.0 .