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# query_module() - Unix, Linux System Call

# 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);

# DESCRIPTION

query_module() requests information from the kernel about loadable modules. 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 currently loaded module, some allow name to be NULL, indicating the kernel proper.

The following values can be specified for which:

Tag | Description
--- | ---
0 | Always returns success. 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, etc. that indicates the current status of the module (see the kernel source file include/linux/module.h). ret is set to the size of the module_info structure.

# RETURN VALUE

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

# ERRORS

Tag | Description
--- | ---
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 minimum size needed.

# CONFORMING TO

query_module() is Linux specific.

# NOTES

This system call is only present on Linux up until kernel 2.4; it was removed in Linux 2.6. Some of the information that was available via query_module() can be obtained from /proc/modules, /proc/kallsyms, and /sys/modules.

# SEE ALSO

- create_module (2)

- get_kernel_syms (2)

- init_module (2)

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