man2/delete_module.2

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  23 .TH DELETE_MODULE 2 2012-10-24 "Linux" "Linux Programmer's Manual"
  24 .SH NAME
  25 delete_module \- unload a kernel module
  26 .SH SYNOPSIS
  27 .nf
  28 .BI "int delete_module(const char *" name ", int " flags );
  29 .fi
  30
  31 .IR Note :
  32 There is no glibc wrapper for this system call; see NOTES.
  33 .SH DESCRIPTION
  34 The
  35 .BR delete_module ()
  36 system call attempts to remove the unused loadable module entry
  37 identified by
  38 .IR name .
  39 If the module has an
  40 .I exit
  41 function, then that function is executed before unloading the module.
  42 The
  43 .IR flags
  44 argument is used to modify the behavior of the system call,
  45 as described below.
  46 This system call requires privilege.
  47
  48 Module removal is attempted according to the following rules:
  49 .IP 1. 4
  50 If there are other loaded modules that depend on
  51 (i.e., refer to symbols defined in) this module,
  52 then the call fails.
  53 .IP 2.
  54 Otherwise, if the reference count for the module
  55 (i.e., the  number  of processes currently using the module)
  56 is zero, then the module is immediately unloaded.
  57 .IP 3.
  58 If a module has a nonzero reference count,
  59 then the behavior depends on the bits set in
  60 .IR flags .
  61 In normal usage (see NOTES), the
  62 .BR O_NONBLOCK
  63 flag is always specified, and the
  64 .BR O_TRUNC
  65 flag may additionally be specified.
  66 .\"     O_TRUNC == KMOD_REMOVE_FORCE in kmod library
  67 .\"     O_NONBLOCK == KMOD_REMOVE_NOWAIT in kmod library
  68
  69 The various combinations for
  70 .I flags
  71 have the following effect:
  72 .RS 4
  73 .TP
  74 .B flags == O_NONBLOCK
  75 The call returns immediately, with an error.
  76 .TP
  77 .B flags == (O_NONBLOCK | O_TRUNC)
  78 The module is unloaded immediately,
  79 regardless of whether it has a nonzero reference count.
  80 .TP
  81 .B (flags & O_NONBLOCK) == 0
  82 If
  83 .I flags
  84 does not specify
  85 .BR O_NONBLOCK ,
  86 the following steps occur:
  87 .RS
  88 .IP * 3
  89 The module is marked so that no new references are permitted.
  90 .IP *
  91 If the module's reference count is nonzero,
  92 the caller is placed in an uninterruptible sleep state
  93 .RB ( TASK_UNINTERRUPTIBLE )
  94 until the reference count is zero, at which point the call unblocks.
  95 .IP *
  96 The module is unloaded in the usual way.
  97 .RE
  98 .RE
  99 .PP
 100 The
 101 .B O_TRUNC
 102 flag has one further effect on the rules described above.
 103 By default,
 104 attempting to remove a module that has an
 105 .I init
 106 function but no
 107 .I exit
 108 function fails.
 109 However, if
 110 .BR O_TRUNC
 111 was specified, this requirement is bypassed.
 112 .PP
 113 Using the
 114 .B O_TRUNC
 115 flag is dangerous!
 116 If the kernel was not built with
 117 .BR CONFIG_MODULE_FORCE_UNLOAD ,
 118 this flag is silently ignored.
 119 (Normally,
 120 .BR CONFIG_MODULE_FORCE_UNLOAD
 121 is enabled.)
 122 Using this flag taints the kernel (TAINT_FORCED_RMMOD).
 123 .SH "RETURN VALUE"
 124 On success, zero is returned.
 125 On error, \-1 is returned and
 126 .I errno
 127 is set appropriately.
 128 .SH ERRORS
 129 .TP
 130 .B EBUSY
 131 The module is not "live"
 132 (i.e., it is still being initialized or is already marked for removal);
 133 or, the module has
 134 an
 135 .I init
 136 function but has no
 137 .I exit
 138 function, and
 139 .B O_TRUNC
 140 was not specified in
 141 .IR flags .
 142
 143 .TP
 144 .B EFAULT
 145 .I name
 146 refers to a location outside the process's accessible address space.
 147 .TP
 148 .B ENOENT
 149 No module by that name exists.
 150 .TP
 151 .B EPERM
 152 The caller was not privileged
 153 (did not have the
 154 .B CAP_SYS_MODULE
 155 capability),
 156 or module unloading is disabled
 157 (see
 158 .IR /proc/sys/kernel/modules_disabled
 159 in
 160 .BR proc (5)).
 161 .TP
 162 .B EWOULDBLOCK
 163 Other modules depend on this module;
 164 or,
 165 .BR O_NONBLOCK
 166 was specified in
 167 .IR flags ,
 168 but the reference count of this module is nonzero and
 169 .B O_TRUNC
 170 was not specified in
 171 .IR flags .
 172 .SH "CONFORMING TO"
 173 .BR delete_module ()
 174 is Linux-specific.
 175 .SH NOTES
 176 Glibc does not provide a wrapper for this system call; call it using
 177 .BR syscall (2).
 178
 179 The uninterruptible sleep that may occur if
 180 .BR O_NONBLOCK
 181 is omitted from
 182 .IR flags
 183 is considered undesirable, because the sleeping process is left
 184 in an unkillable state.
 185 As at Linux 3.7, specifying
 186 .BR O_NONBLOCK
 187 is optional, but in future kernels it is likely to become mandatory.
 188 .SS Linux 2.4 and earlier
 189 In Linux 2.4 and earlier, the system call took only one argument:
 190
 191 .BI "   int delete_module(const char *" name );
 192
 193 If
 194 .I name
 195 is NULL, all unused modules marked auto-clean are removed.
 196
 197 Some further details of differences in the behavior of
 198 .BR delete_module ()
 199 in Linux 2.4 and earlier are
 200 .I not
 201 currently explained in this manual page.
 202 .SH "SEE ALSO"
 203 .BR create_module (2),
 204 .BR init_module (2),
 205 .BR query_module (2),
 206 .BR lsmod (8),
 207 .BR modprobe (8),
 208 .BR rmmod (8)