134 lines
3.9 KiB
Groff
134 lines
3.9 KiB
Groff
.\"
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.\" Copyright (c) 1998 John D. Polstra
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 5, 1998
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.Os
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.Dt DLADDR 3
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.Sh NAME
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.Nm dladdr
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.Nd find the shared object containing a given address
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In dlfcn.h
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.Ft int
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.Fn dladdr "const void *addr" "Dl_info *info"
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.Sh DESCRIPTION
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The
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.Fn dladdr
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function
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queries the dynamic linker for information about the shared object
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containing the address
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.Fa addr .
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The information is returned in the structure specified by
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.Fa info .
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The structure contains at least the following members:
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.Bl -tag -width "XXXconst char *dli_fname"
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.It Li "const char *dli_fname"
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The pathname of the shared object containing the address.
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.It Li "void *dli_fbase"
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The base address at which the shared object is mapped into the
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address space of the calling process.
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.It Li "const char *dli_sname"
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The name of the nearest run-time symbol with a value less than or
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equal to
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.Fa addr .
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When possible, the symbol name is returned as it would appear in C
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source code.
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.Pp
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If no symbol with a suitable value is found, both this field and
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.Va dli_saddr
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are set to
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.Dv NULL .
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.It Li "void *dli_saddr"
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The value of the symbol returned in
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.Li dli_sname .
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.El
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.Pp
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The
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.Fn dladdr
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function
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is available only in dynamically linked programs.
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.Sh ERRORS
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If a mapped shared object containing
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.Fa addr
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cannot be found,
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.Fn dladdr
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returns 0.
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In that case, a message detailing the failure can be retrieved by
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calling
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.Fn dlerror .
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.Pp
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On success, a non-zero value is returned.
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.Sh SEE ALSO
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.Xr rtld 1 ,
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.Xr dlopen 3
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.Sh HISTORY
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The
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.Fn dladdr
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function first appeared in the Solaris operating system.
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.Sh BUGS
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This implementation is bug-compatible with the Solaris
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implementation.
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In particular, the following bugs are present:
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.Bl -bullet
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.It
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If
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.Fa addr
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lies in the main executable rather than in a shared library, the
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pathname returned in
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.Va dli_fname
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may not be correct.
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The pathname is taken directly from
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.Va argv[0]
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of the calling process.
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When executing a program specified by its
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full pathname, most shells set
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.Va argv[0]
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to the pathname.
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But this is not required of shells or guaranteed
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by the operating system.
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.It
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If
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.Fa addr
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is of the form
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.Va &func ,
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where
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.Va func
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is a global function, its value may be an unpleasant surprise.
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In
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dynamically linked programs, the address of a global function is
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considered to point to its program linkage table entry, rather than to
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the entry point of the function itself.
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This causes most global
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functions to appear to be defined within the main executable, rather
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than in the shared libraries where the actual code resides.
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.It
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Returning 0 as an indication of failure goes against long-standing
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Unix tradition.
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.El
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