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.\" Copyright (C) 1996 Free Software Foundation, Inc.
.\" This file is distributed according to the GNU General Public License.
.\" See the file COPYING in the top level source directory for details.
.\"
.\" 2006-02-09, some reformatting by Luc Van Oostenryck; some
.\" reformatting and rewordings by mtk
.\"
.TH QUERY_MODULE 2 "2002" "Linux" "Linux Module Support"
.SH NAME
query_module \- query the kernel for various bits pertaining to modules
.SH SYNOPSIS
.nf
.B #include <linux/module.h>
.sp
.BI "int query_module(const char *" name ", int " which ", void *" buf ,
.BI " size_t " bufsize ", size_t *" ret );
.fi
.SH DESCRIPTION
.BR query_module ()
requests information from the kernel about loadable modules.
The returned information is placed in the buffer pointed to by
.IR buf .
The caller must specify the size of
.I buf
in
.IR bufsize .
The precise nature and format of the returned information
depend on the operation specified by
.IR which .
Some operations require
.I name
to identify a currently loaded module, some allow
.I name
to be NULL, indicating the kernel proper.
The following values can be specified for
.IR which :
.TP
.B 0
Always returns success.
Used to probe for availability of the system call.
.TP
.B QM_MODULES
Returns the names of all loaded modules.
The returned buffer consists of a sequence of null-terminated strings;
.I ret
is set to the number of
modules.
.TP
.B QM_DEPS
Returns the names of all modules used by the indicated module.
The returned buffer consists of a sequence of null-terminated strings;
.I ret
is set to the number of modules.
.TP
.B QM_REFS
Returns the names of all modules using the indicated module. This is
the inverse of
.BR QM_DEPS .
The returned buffer consists of a sequence of null-terminated strings;
.I ret
is set to the number of modules.
.TP
.B QM_SYMBOLS
Returns the symbols and values exported by the kernel or the indicated
module.
The returned buffer is an array of structures of the following form
.RS
.PP
.nf
struct module_symbol {
unsigned long value;
unsigned long name;
};
.fi
.PP
followed by null-terminated strings.
The value of
.I name
is the character offset of the string relative to the start of
.IR buf ;
.I ret
is set to the number of symbols.
.RE
.TP
.B QM_INFO
Returns miscellaneous information about the indicated module. The output
buffer format is:
.RS
.PP
.nf
struct module_info {
unsigned long address;
unsigned long size;
unsigned long flags;
};
.fi
.PP
where
.I address
is the kernel address at which the module resides,
.I size
is the size of the module in bytes, and
.I flags
is a mask of
.BR MOD_RUNNING ,
.BR MOD_AUTOCLEAN ,
etc. that indicates the current status of the module
(see the kernel source file
.IR include/linux/module.h ).
.I ret
is set to the size of the
.I module_info
structure.
.RE
.SH "RETURN VALUE"
On success, zero is returned. On error, \-1 is returned and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EFAULT
At least one of
.IR name ,
.IR buf ,
or
.I ret
was outside the program's accessible address space.
.TP
.B EINVAL
Invalid
.IR which ;
or
.I name
is NULL (indicating "the kernel"),
but this is not permitted with the specified value of
.IR which .
.\" Not permitted with QM_DEPS, QM_REFS, or QM_INFO.
.TP
.B ENOENT
No module by that
.I name
exists.
.TP
.B ENOSPC
The buffer size provided was too small.
.I ret
is set to the minimum size needed.
.SH "CONFORMING TO"
.BR query_module ()
is Linux specific.
.SH NOTES
This system call is only present on Linux up until kernel 2.4;
it was removed in Linux 2.6.
.\" Removed in Linux-2.5.48
Some of the information that was available via
.BR query_module ()
can be obtained from
.IR /proc/modules ,
.IR /proc/kallsyms ,
and
.IR /sys/modules .
.SH "SEE ALSO"
.BR create_module (2),
.BR delete_module (2),
.BR get_kernel_syms (2),
.BR init_module (2)
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