knlist(3)knlist(3)NAMEknlist - look up symbols in the currently running kernel
SYNOPSIS
#include <nlist.h>
int knlist(
struct nlist namelist );
LIBRARY
Standard C Library (libc.a, libc.so)
PARAMETERS
On input, lists the symbol names for which you are requesting
addresses. The namelist must be terminated with a null name at end.
Without a terminating null name at end, knlist() cannot determine how
many symbols are in the namelist and therefore may dump core.
On return, contains a list of symbol addresses (or 0 if the
attempt to find the addresses was unsuccessful).
DESCRIPTION
The knlist() library routine looks up addresses of kernel symbols in
the currently running kernel. In addition to finding symbols associated
with the kernel image, knlist() will also find symbols defined in
dynamically loaded subsystems.
Communication with the knlist() routine occurs using an array of type
struct nlist. The <nlist.h> header file declares that type as follows:
struct nlist {
char *n_name;
unsigned long n_value;
short n_type; /* 0 if not there, 1 if found */
short reserved; };
When your application calls knlist(), it passes the names of symbols in
the n_name field of the structure.
For each symbol, the knlist() routine attempts to determine its current
address in memory. If the routine can determine the address of the sym‐
bol, it returns that address in the n_value field, and it returns one
(1) in the n_type field. If the routine cannot determine the address,
it returns zero (0) in both the n_value field and the n_type field.
For BSD compatibility, the knlist() routine allows symbol names to be
preceded by an underscore. If it does not find a symbol that matches
the name as specified, knlist() attempts to locate the symbol name with
the leading underscore removed.
RETURN VALUES
The knlist() routine returns zero on success. The routine returns -1 if
it was unable to connect to the kloadsrv daemon. In this case, the rou‐
tine was unable to determine any of the requested addresses. The rou‐
tine returns a positive integer if it successfully finds some addresses
and fails to find others. The integer value indicates the number of
addresses knlist() was unable to return.
The routine returns the negative value of EINVAL if the argument is
bad.
EXAMPLES
The following example illustrates the use of the knlist() routine:
#include <stdio.h> #include <string.h> #include <stdlib.h> #include
<nlist.h> main () {
struct nlist nl[3];
int retval, i;
nl[0].n_name = (char *)malloc(10);
nl[1].n_name = (char *)malloc(10);
nl[2].n_name = ;
/*******************************************************/
/* Store names of kernel symbols in the nl array */
strcpy (nl[0].n_name, "ncpus");
strcpy (nl[1].n_name, "lockmode");
/*******************************************************/
/* Call the knlist routine */
retval = knlist(nl);
/******************************************************/
/* Display addresses if returned. Otherwise, display */
/* the appropriate error message. */
if (retval < 0)
printf ("No kernel symbol addresses returned.\n");
else
if (retval >= 0 )
for (i=0; i<2; i++)
if (nl[i].n_type == 0)
printf ("Unable to return address of symbol %s\n",
nl[i].n_name);
else
printf ("The address of symbol %s is %lx\n",
nl[i].n_name, nl[i].n_value);
free (nl[0].n_name);
free (nl[1].n_name); }
This example tests the return value from the knlist() routine. If the
routine returns an error status, a message is displayed to the applica‐
tion user. Otherwise, the application checks the status of each kernel
symbol. If the knlist() routine was unable to return an address, the
application displays a message and the symbol name. If the knlist()
routine returns an address, the application displays the symbol name
and address to the application user.
SEE ALSO
Routines: nlist(3)knlist(3)