man2/uselib.2

   1 .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
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  25 .\" Modified by Michael Haardt <michael@moria.de>
  26 .\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
  27 .\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
  28 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
  29 .\" Modified 2005-01-09 by aeb
  30 .\"
  31 .TH USELIB 2 2017-09-15 "Linux" "Linux Programmer's Manual"
  32 .SH NAME
  33 uselib \- load shared library
  34 .SH SYNOPSIS
  35 .B #include <unistd.h>
  36 .PP
  37 .BI "int uselib(const char *" library );
  38 .PP
  39 .IR Note :
  40 No declaration of this system call is provided in glibc headers; see NOTES.
  41 .SH DESCRIPTION
  42 The system call
  43 .BR uselib ()
  44 serves to load
  45 a shared library to be used by the calling process.
  46 It is given a pathname.
  47 The address where to load is found
  48 in the library itself.
  49 The library can have any recognized
  50 binary format.
  51 .SH RETURN VALUE
  52 On success, zero is returned.
  53 On error, \-1 is returned, and
  54 .I errno
  55 is set appropriately.
  56 .SH ERRORS
  57 In addition to all of the error codes returned by
  58 .BR open (2)
  59 and
  60 .BR mmap (2),
  61 the following may also be returned:
  62 .TP
  63 .B EACCES
  64 The library specified by
  65 .I library
  66 does not have read or execute permission, or the caller does not have
  67 search permission for one of the directories in the path prefix.
  68 (See also
  69 .BR path_resolution (7).)
  70 .TP
  71 .B ENFILE
  72 The system-wide limit on the total number of open files has been reached.
  73 .TP
  74 .B ENOEXEC
  75 The file specified by
  76 .I library
  77 is not an executable of a known type;
  78 for example, it does not have the correct magic numbers.
  79 .SH CONFORMING TO
  80 .BR uselib ()
  81 is Linux-specific, and should not be used in programs
  82 intended to be portable.
  83 .SH NOTES
  84 This obsolete system call is not supported by glibc.
  85 No declaration is provided in glibc headers, but, through a quirk of history,
  86 glibc versions before 2.23 did export an ABI for this system call.
  87 Therefore, in order to employ this system call,
  88 it was sufficient to manually declare the interface in your code;
  89 alternatively, you could invoke the system call using
  90 .BR syscall (2).
  91 .PP
  92 In ancient libc versions,
  93 .BR uselib ()
  94 was used to load
  95 the shared libraries with names found in an array of names
  96 in the binary.
  97 .PP
  98 .\" libc 4.3.1f - changelog 1993-03-02
  99 Since libc 4.3.2, startup code tries to prefix these names
 100 with "/usr/lib", "/lib" and "" before giving up.
 101 .\" libc 4.3.4 - changelog 1993-04-21
 102 In libc 4.3.4 and later these names are looked for in the directories
 103 found in
 104 .BR LD_LIBRARY_PATH ,
 105 and if not found there,
 106 prefixes "/usr/lib", "/lib" and "/" are tried.
 107 .PP
 108 From libc 4.4.4 on only the library "/lib/ld.so" is loaded,
 109 so that this dynamic library can load the remaining libraries needed
 110 (again using this call).
 111 This is also the state of affairs in libc5.
 112 .PP
 113 glibc2 does not use this call.
 114 .PP
 115 Since Linux 3.15,
 116 .\" commit 69369a7003735d0d8ef22097e27a55a8bad9557a
 117 this system call is available only when the kernel is configured with the
 118 .B CONFIG_USELIB
 119 option.
 120 .SH SEE ALSO
 121 .BR ar (1),
 122 .BR gcc (1),
 123 .BR ld (1),
 124 .BR ldd (1),
 125 .BR mmap (2),
 126 .BR open (2),
 127 .BR dlopen (3),
 128 .BR capabilities (7),
 129 .BR ld.so (8)