man2/delete_module.2

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  23 .TH DELETE_MODULE 2 2012-11-08 "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, if a module has an
 104 .I init
 105 function but no
 106 .I exit
 107 function, then an attempt to remove the module will fail.
 108 However, if
 109 .BR O_TRUNC
 110 was specified, this requirement is bypassed.
 111 .PP
 112 Using the
 113 .B O_TRUNC
 114 flag is dangerous!
 115 If the kernel was not built with
 116 .BR CONFIG_MODULE_FORCE_UNLOAD ,
 117 this flag is silently ignored.
 118 (Normally,
 119 .BR CONFIG_MODULE_FORCE_UNLOAD
 120 is enabled.)
 121 Using this flag taints the kernel (TAINT_FORCED_RMMOD).
 122 .SH "RETURN VALUE"
 123 On success, zero is returned.
 124 On error, \-1 is returned and
 125 .I errno
 126 is set appropriately.
 127 .SH ERRORS
 128 .TP
 129 .B EBUSY
 130 The module is not "live"
 131 (i.e., it is still being initialized or is already marked for removal);
 132 or, the module has
 133 an
 134 .I init
 135 function but has no
 136 .I exit
 137 function, and
 138 .B O_TRUNC
 139 was not specified in
 140 .IR flags .
 141
 142 .TP
 143 .B EFAULT
 144 .I name
 145 refers to a location outside the process's accessible address space.
 146 .TP
 147 .B ENOENT
 148 No module by that name exists.
 149 .TP
 150 .B EPERM
 151 The caller was not privileged
 152 (did not have the
 153 .B CAP_SYS_MODULE
 154 capability),
 155 or module unloading is disabled
 156 (see
 157 .IR /proc/sys/kernel/modules_disabled
 158 in
 159 .BR proc (5)).
 160 .TP
 161 .B EWOULDBLOCK
 162 Other modules depend on this module;
 163 or,
 164 .BR O_NONBLOCK
 165 was specified in
 166 .IR flags ,
 167 but the reference count of this module is nonzero and
 168 .B O_TRUNC
 169 was not specified in
 170 .IR flags .
 171 .SH "CONFORMING TO"
 172 .BR delete_module ()
 173 is Linux-specific.
 174 .SH NOTES
 175 Glibc does not provide a wrapper for this system call; call it using
 176 .BR syscall (2).
 177
 178 The uninterruptible sleep that may occur if
 179 .BR O_NONBLOCK
 180 is omitted from
 181 .IR flags
 182 is considered undesirable, because the sleeping process is left
 183 in an unkillable state.
 184 As at Linux 3.7, specifying
 185 .BR O_NONBLOCK
 186 is optional, but in future kernels it is likely to become mandatory.
 187 .SS Linux 2.4 and earlier
 188 In Linux 2.4 and earlier, the system call took only one argument:
 189
 190 .BI "   int delete_module(const char *" name );
 191
 192 If
 193 .I name
 194 is NULL, all unused modules marked auto-clean are removed.
 195
 196 Some further details of differences in the behavior of
 197 .BR delete_module ()
 198 in Linux 2.4 and earlier are
 199 .I not
 200 currently explained in this manual page.
 201 .SH "SEE ALSO"
 202 .BR create_module (2),
 203 .BR init_module (2),
 204 .BR query_module (2),
 205 .BR lsmod (8),
 206 .BR modprobe (8),
 207 .BR rmmod (8)