GENWiki

QUERY_MODULE(2) Linux Programmer's Manual QUERY_MODULE(2)

NAME

     query_module - query the kernel for various bits pertaining to modules

SYNOPSIS

     #include <linux/module.h>

     int query_module(const char *name, int which, void *buf,
                      size_t bufsize, size_t *ret);

     Note:  No declaration of this system call is provided in glibc headers;
     see NOTES.

DESCRIPTION

     Note: This system call is present only in kernels before Linux 2.6.

     query_module() requests information from the kernel about loadable mod-
     ules.   The  returned information is placed in the buffer pointed to by
     buf.  The caller must specify the size of buf in bufsize.  The  precise
     nature  and  format of the returned information depend on the operation
     specified by which.  Some operations require name to  identify  a  cur-
     rently loaded module, some allow name to be NULL, indicating the kernel
     proper.

     The following values can be specified for which:

     0      Returns success, if the kernel supports query_module().  Used to
            probe for availability of the system call.

     QM_MODULES
            Returns  the  names  of all loaded modules.  The returned buffer
            consists of a sequence of null-terminated strings; ret is set to
            the number of modules.

     QM_DEPS
            Returns  the  names of all modules used by the indicated module.
            The returned buffer consists of a  sequence  of  null-terminated
            strings; ret is set to the number of modules.

     QM_REFS
            Returns  the  names  of  all modules using the indicated module.
            This is the inverse of QM_DEPS.  The returned buffer consists of
            a  sequence of null-terminated strings; ret is set to the number
            of modules.

     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

                struct module_symbol {
                    unsigned long value;
                    unsigned long name; };

            followed by null-terminated strings.  The value of name  is  the
            character offset of the string relative to the start of buf; ret
            is set to the number of symbols.

     QM_INFO
            Returns miscellaneous information about  the  indicated  module.
            The output buffer format is:

                struct module_info {
                    unsigned long address;
                    unsigned long size;
                    unsigned long flags; };

            where address is the kernel address at which the module resides,
            size is the size of the module in bytes, and flags is a mask  of
            MOD_RUNNING,  MOD_AUTOCLEAN,  and so on, that indicates the cur-
            rent status of the module (see  the  Linux  kernel  source  file
            include/linux/module.h).   ret  is  set  to the size of the mod-
            ule_info structure.

RETURN VALUE

     On success, zero is returned.  On error, -1 is returned  and  errno  is
     set appropriately.

ERRORS

     EFAULT At  least  one  of  name,  buf, or ret was outside the program's
            accessible address space.

     EINVAL Invalid which; or name is NULL (indicating  "the  kernel"),  but
            this is not permitted with the specified value of which.

     ENOENT No module by that name exists.

     ENOSPC The buffer size provided was too small.  ret is set to the mini-
            mum size needed.

     ENOSYS query_module() is not supported in this version  of  the  kernel
            (e.g., the kernel is version 2.6 or later).

VERSIONS

     This  system  call is present on Linux only up until kernel 2.4; it was
     removed in Linux 2.6.

CONFORMING TO

     query_module() is Linux-specific.

NOTES

     Some of the information that was formerly available via  query_module()
     can be obtained from /proc/modules, /proc/kallsyms, and the files under
     the directory /sys/module.

     The query_module() system call is not supported by glibc.  No  declara-
     tion  is  provided  in  glibc headers, but, through a quirk of history,
     glibc does export an ABI for this system call.  Therefore, in order  to
     employ  this  system  call,  it  is  sufficient to manually declare the
     interface in your code; alternatively, you can invoke the  system  call
     using syscall(2).