1994-12-23 22:41:46 +00:00
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.\" Copyright (c) 1993 Paul Kranenburg
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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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Paul Kranenburg.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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1999-08-28 00:22:10 +00:00
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.\" $FreeBSD$
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1994-12-23 22:41:46 +00:00
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.\"
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.Dd October 23, 1993
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.Dt LINK 5
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.Os
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.Sh NAME
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.Nm link
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.Nd dynamic loader and link editor interface
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.Sh SYNOPSIS
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1996-05-01 01:45:23 +00:00
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.Fd #include <sys/types.h>
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.Fd #include <nlist.h>
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1994-12-23 22:41:46 +00:00
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.Fd #include <link.h>
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.Sh DESCRIPTION
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The include file
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.Aq Pa link.h
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declares several structures that are present in dynamically linked
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programs and libraries.
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The structures define the interface between several components of the
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2000-03-02 14:54:02 +00:00
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link-editor and loader mechanism.
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The layout of a number of these
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1994-12-23 22:41:46 +00:00
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structures within the binaries resembles the a.out format in many places
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as it serves such similar functions as symbol definitions (including the
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accompanying string table) and relocation records needed to resolve
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2000-03-02 14:54:02 +00:00
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references to external entities.
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It also records a number of data structures
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unique to the dynamic loading and linking process.
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These include references
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1994-12-23 22:41:46 +00:00
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to other objects that are required to complete the link-editing process and
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indirection tables to facilitate
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.Em Position Independent Code
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(PIC for short) to improve sharing of code pages among different processes.
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1996-01-30 13:52:50 +00:00
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The collection of data structures described here will be referred to as the
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1994-12-23 22:41:46 +00:00
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.Em Run-time Relocation Section (RRS)
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and is embedded in the standard text and data segments of the dynamically
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linked program or shared object image as the existing
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1996-04-08 04:18:31 +00:00
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.Xr a.out 5
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1994-12-23 22:41:46 +00:00
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format offers no room for it elsewhere.
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.Pp
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Several utilities cooperate to ensure that the task of getting a program
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ready to run can complete successfully in a way that optimizes the use
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2000-03-02 14:54:02 +00:00
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of system resources.
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The compiler emits PIC code from which shared libraries
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1996-01-20 07:29:11 +00:00
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can be built by
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.Xr ld 1 .
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1994-12-23 22:41:46 +00:00
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The compiler also includes size information of any initialized data items
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2000-03-02 14:54:02 +00:00
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through the .size assembler directive.
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PIC code differs from conventional code
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1994-12-23 22:41:46 +00:00
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in that it accesses data variables through an indirection table, the
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1996-01-30 13:52:50 +00:00
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Global Offset Table, by convention accessible by the reserved name
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2001-02-01 16:38:02 +00:00
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.Dv _GLOBAL_OFFSET_TABLE_ .
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1994-12-23 22:41:46 +00:00
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The exact mechanism used for this is machine dependent, usually a machine
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2000-03-02 14:54:02 +00:00
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register is reserved for the purpose.
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The rational behind this construct
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is to generate code that is independent of the actual load address.
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Only
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1994-12-23 22:41:46 +00:00
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the values contained in the Global Offset Table may need updating at run-time
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depending on the load addresses of the various shared objects in the address
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space.
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.Pp
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Likewise, procedure calls to globally defined functions are redirected through
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the Procedure Linkage Table (PLT) residing in the data segment of the core
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2000-03-02 14:54:02 +00:00
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image.
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Again, this is done to avoid run-time modifications to the text segment.
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1994-12-23 22:41:46 +00:00
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.Pp
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The linker-editor allocates the Global Offset Table and Procedure Linkage Table
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when combining PIC object files into an image suitable for mapping into the
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2000-03-02 14:54:02 +00:00
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process address space.
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It also collects all symbols that may be needed by the
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1994-12-23 22:41:46 +00:00
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run-time link-editor and stores these along with the image's text and data bits.
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Another reserved symbol,
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.Em _DYNAMIC
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2000-03-02 14:54:02 +00:00
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is used to indicate the presence of the run-time linker structures.
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Whenever
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1994-12-23 22:41:46 +00:00
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_DYNAMIC is relocated to 0, there is no need to invoke the run-time
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2000-03-02 14:54:02 +00:00
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link-editor.
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If this symbol is non-zero, it points at a data structure from
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1994-12-23 22:41:46 +00:00
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which the location of the necessary relocation- and symbol information can
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2000-03-02 14:54:02 +00:00
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be derived.
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This is most notably used by the start-up module,
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2001-02-01 16:38:02 +00:00
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.Em crt0 .
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1994-12-23 22:41:46 +00:00
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The _DYNAMIC structure is conventionally located at the start of the data
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segment of the image to which it pertains.
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.Sh DATA STRUCTURES
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The data structures supporting dynamic linking and run-time relocation
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reside both in the text and data segments of the image they apply to.
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The text segments contain read-only data such as symbols descriptions and
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names, while the data segments contain the tables that need to be modified by
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during the relocation process.
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.Pp
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The _DYNAMIC symbol references a
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.Fa _dynamic
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structure:
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.Bd -literal -offset indent
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struct _dynamic {
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int d_version;
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struct so_debug *d_debug;
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union {
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struct section_dispatch_table *d_sdt;
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} d_un;
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struct ld_entry *d_entry;
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};
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.Ed
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.Bl -tag -width d_version
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.It Fa d_version
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This field provides for different versions of the dynamic linking
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2000-03-02 14:54:02 +00:00
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implementation.
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The current version numbers understood by
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1996-04-08 04:18:31 +00:00
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.Xr ld 1
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and
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.Xr ld.so 1
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are
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2001-02-01 16:38:02 +00:00
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.Em LD_VERSION_SUN (3) ,
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1997-03-21 20:14:15 +00:00
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which is used by the
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.Tn SunOS
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4.x releases, and
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2001-02-01 16:38:02 +00:00
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.Em LD_VERSION_BSD (8) ,
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1997-03-21 20:14:15 +00:00
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which has been in use since
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.Fx 1.1 .
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1994-12-23 22:41:46 +00:00
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.It Fa d_un
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Refers to a
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.Em d_version
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dependent data structure.
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.It Fa so_debug
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this field provides debuggers with a hook to access symbol tables of shared
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objects loaded as a result of the actions of the run-time link-editor.
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.El
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.Pp
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The
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.Fa section_dispatch_table
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structure is the main
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.Dq dispatcher
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table, containing offsets into the image's segments where various symbol
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and relocation information is located.
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.Bd -literal -offset indent
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struct section_dispatch_table {
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struct so_map *sdt_loaded;
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long sdt_sods;
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long sdt_filler1;
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long sdt_got;
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long sdt_plt;
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long sdt_rel;
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long sdt_hash;
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long sdt_nzlist;
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long sdt_filler2;
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long sdt_buckets;
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long sdt_strings;
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long sdt_str_sz;
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long sdt_text_sz;
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long sdt_plt_sz;
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};
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.Ed
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.Pp
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.Bl -tag -width sdt_filler1
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.It Fa sdt_loaded
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A pointer to the first link map loaded (see below). This field is set by
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1996-04-08 04:18:31 +00:00
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.Nm ld.so
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1994-12-23 22:41:46 +00:00
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.It Fa sdt_sods
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The start of a (linked) list of shared object descriptors needed by
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.Em this
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object.
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.It Fa sdt_filler1
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1996-01-30 13:52:50 +00:00
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Deprecated (used by SunOS to specify library search rules).
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1994-12-23 22:41:46 +00:00
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.It Fa sdt_got
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The location of the Global Offset Table within this image.
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.It Fa sdt_plt
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The location of the Procedure Linkage Table within this image.
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.It Fa sdt_rel
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The location of an array of
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.Fa relocation_info
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structures
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.Po
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see
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.Xr a.out 5
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.Pc
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specifying run-time relocations.
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.It Fa sdt_hash
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The location of the hash table for fast symbol lookup in this object's
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symbol table.
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.It Fa sdt_nzlist
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The location of the symbol table.
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.It Fa sdt_filler2
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Currently unused.
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.It Fa sdt_buckets
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The number of buckets in
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.Fa sdt_hash
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.It Fa sdt_strings
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The location of the symbol string table that goes with
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2001-02-01 16:38:02 +00:00
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.Fa sdt_nzlist .
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1994-12-23 22:41:46 +00:00
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.It Fa sdt_str_sz
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The size of the string table.
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.It Fa sdt_text_sz
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The size of the object's text segment.
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.It Fa sdt_plt_sz
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The size of the Procedure Linkage Table.
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.El
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.Pp
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A
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.Fa sod
|
1996-01-30 13:52:50 +00:00
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structure describes a shared object that is needed
|
1994-12-23 22:41:46 +00:00
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to complete the link edit process of the object containing it.
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A list of such objects
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.Po
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chained through
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.Fa sod_next
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.Pc
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is pointed at
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by the
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.Fa sdt_sods
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in the section_dispatch_table structure.
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.Bd -literal -offset indent
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struct sod {
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long sod_name;
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u_int sod_library : 1,
|
1995-04-16 12:35:13 +00:00
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sod_reserved : 31;
|
1994-12-23 22:41:46 +00:00
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short sod_major;
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short sod_minor;
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long sod_next;
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};
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.Ed
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.Pp
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.Bl -tag -width sod_library
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.It Fa sod_name
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The offset in the text segment of a string describing this link object.
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.It Fa sod_library
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If set,
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.Fa sod_name
|
1996-04-08 04:18:31 +00:00
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specifies a library that is to be searched for by
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.Nm ld.so .
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The path name
|
1994-12-23 22:41:46 +00:00
|
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is obtained by searching a set of directories
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.Po
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see also
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|
.Xr ldconfig 8
|
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.Pc
|
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for a shared object matching
|
2001-02-01 16:38:02 +00:00
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.Em lib\&<sod_name>\&.so.n.m .
|
1994-12-23 22:41:46 +00:00
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If not set,
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.Fa sod_name
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should point at a full path name for the desired shared object.
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.It Fa sod_major
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Specifies the major version number of the shared object to load.
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.It Fa sod_minor
|
2001-02-20 10:30:22 +00:00
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Specifies the preferred minor version number of the shared object to load.
|
1994-12-23 22:41:46 +00:00
|
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.El
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.Pp
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The run-time link-editor maintains a list of structures called
|
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.Em link maps
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to keep track of all shared objects loaded into a process' address space.
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These structures are only used at run-time and do not occur within
|
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the text or data segment of an executable or shared library.
|
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.Bd -literal -offset indent
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struct so_map {
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caddr_t som_addr;
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char *som_path;
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struct so_map *som_next;
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struct sod *som_sod;
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caddr_t som_sodbase;
|
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u_int som_write : 1;
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struct _dynamic *som_dynamic;
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|
caddr_t som_spd;
|
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};
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.Ed
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|
.Bl -tag -width som_dynamic
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.It Fa som_addr
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The address at which the shared object associated with this link map has
|
|
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been loaded.
|
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.It Fa som_path
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The full path name of the loaded object.
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.It Fa som_next
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Pointer to the next link map.
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|
.It Fa som_sod
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The
|
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.Fa sod
|
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|
structure that was responsible for loading this shared object.
|
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|
.It Fa som_sodbase
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Tossed in later versions the run-time linker.
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.It Fa som_write
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Set if (some portion of) this object's text segment is currently writable.
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.It Fa som_dynamic
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Pointer to this object's
|
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|
.Fa _dynamic
|
|
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structure.
|
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|
.It Fa som_spd
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|
Hook for attaching private data maintained by the run-time link-editor.
|
|
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|
.El
|
|
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|
.Pp
|
2000-03-02 14:54:02 +00:00
|
|
|
Symbol description with size.
|
|
|
|
This is simply an
|
1994-12-23 22:41:46 +00:00
|
|
|
.Fa nlist
|
|
|
|
structure with one field
|
|
|
|
.Pq Fa nz_size
|
2000-03-02 14:54:02 +00:00
|
|
|
added.
|
|
|
|
Used to convey size information on items in the data segment
|
|
|
|
of shared objects.
|
|
|
|
An array of these lives in the shared object's
|
1994-12-23 22:41:46 +00:00
|
|
|
text segment and is addressed by the
|
|
|
|
.Fa sdt_nzlist
|
|
|
|
field of
|
2001-02-01 16:38:02 +00:00
|
|
|
.Fa section_dispatch_table .
|
1994-12-23 22:41:46 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
struct nzlist {
|
|
|
|
struct nlist nlist;
|
|
|
|
u_long nz_size;
|
|
|
|
#define nz_un nlist.n_un
|
|
|
|
#define nz_strx nlist.n_un.n_strx
|
|
|
|
#define nz_name nlist.n_un.n_name
|
|
|
|
#define nz_type nlist.n_type
|
|
|
|
#define nz_value nlist.n_value
|
|
|
|
#define nz_desc nlist.n_desc
|
|
|
|
#define nz_other nlist.n_other
|
|
|
|
};
|
|
|
|
.Ed
|
|
|
|
.Bl -tag -width nz_size
|
|
|
|
.It Fa nlist
|
|
|
|
.Po
|
|
|
|
see
|
1996-04-08 04:18:31 +00:00
|
|
|
.Xr nlist 3
|
1994-12-23 22:41:46 +00:00
|
|
|
.Pc .
|
|
|
|
.It Fa nz_size
|
|
|
|
The size of the data represented by this symbol.
|
|
|
|
.El
|
|
|
|
.Pp
|
|
|
|
A hash table is included within the text segment of shared object to
|
|
|
|
to facilitate quick lookup of symbols during run-time link-editing.
|
|
|
|
The
|
|
|
|
.Fa sdt_hash
|
|
|
|
field of the
|
|
|
|
.Fa section_dispatch_table
|
|
|
|
structure points at an array of
|
|
|
|
.Fa rrs_hash
|
|
|
|
structures:
|
|
|
|
.Bd -literal -offset indent
|
|
|
|
struct rrs_hash {
|
|
|
|
int rh_symbolnum; /* symbol number */
|
|
|
|
int rh_next; /* next hash entry */
|
|
|
|
};
|
|
|
|
.Ed
|
|
|
|
.Pp
|
|
|
|
.Bl -tag -width rh_symbolnum
|
|
|
|
.It Fa rh_symbolnum
|
|
|
|
The index of the symbol in the shared object's symbol table (as given by the
|
|
|
|
.Fa ld_symbols
|
|
|
|
field).
|
|
|
|
.It Fa rh_next
|
|
|
|
In case of collisions, this field is the offset of the next entry in this
|
2000-03-02 14:54:02 +00:00
|
|
|
hash table bucket.
|
|
|
|
It is zero for the last bucket element.
|
1994-12-23 22:41:46 +00:00
|
|
|
.El
|
|
|
|
The
|
|
|
|
.Fa rt_symbol
|
|
|
|
structure is used to keep track of run-time allocated commons
|
2000-03-02 14:54:02 +00:00
|
|
|
and data items copied from shared objects.
|
|
|
|
These items are kept on linked list
|
1994-12-23 22:41:46 +00:00
|
|
|
and is exported through the
|
|
|
|
.Fa dd_cc
|
|
|
|
field in the
|
|
|
|
.Fa so_debug
|
|
|
|
structure (see below) for use by debuggers.
|
|
|
|
.Bd -literal -offset indent
|
|
|
|
struct rt_symbol {
|
|
|
|
struct nzlist *rt_sp;
|
|
|
|
struct rt_symbol *rt_next;
|
|
|
|
struct rt_symbol *rt_link;
|
|
|
|
caddr_t rt_srcaddr;
|
|
|
|
struct so_map *rt_smp;
|
|
|
|
};
|
|
|
|
.Ed
|
|
|
|
.Pp
|
|
|
|
.Bl -tag -width rt_scraddr
|
|
|
|
.It Fa rt_sp
|
|
|
|
The symbol description.
|
|
|
|
.It Fa rt_next
|
|
|
|
Virtual address of next rt_symbol.
|
|
|
|
.It Fa rt_link
|
2000-03-02 14:54:02 +00:00
|
|
|
Next in hash bucket.
|
|
|
|
Used by internally by
|
1996-04-08 04:18:31 +00:00
|
|
|
.Nm ld.so .
|
1994-12-23 22:41:46 +00:00
|
|
|
.It Fa rt_srcaddr
|
|
|
|
Location of the source of initialized data within a shared object.
|
|
|
|
.It Fa rt_smp
|
|
|
|
The shared object which is the original source of the data that this
|
|
|
|
run-time symbol describes.
|
|
|
|
.El
|
|
|
|
.Pp
|
|
|
|
The
|
|
|
|
.Fa so_debug
|
|
|
|
structure is used by debuggers to gain knowledge of any shared objects
|
|
|
|
that have been loaded in the process's address space as a result of run-time
|
2000-03-02 14:54:02 +00:00
|
|
|
link-editing.
|
|
|
|
Since the run-time link-editor runs as a part of process
|
1994-12-23 22:41:46 +00:00
|
|
|
initialization, a debugger that wishes to access symbols from shared objects
|
|
|
|
can only do so after the link-editor has been called from crt0.
|
|
|
|
A dynamically linked binary contains a
|
|
|
|
.Fa so_debug
|
|
|
|
structure which can be located by means of the
|
|
|
|
.Fa d_debug
|
|
|
|
field in
|
1997-01-15 05:33:11 +00:00
|
|
|
.Fa _dynamic .
|
1994-12-23 22:41:46 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
struct so_debug {
|
|
|
|
int dd_version;
|
|
|
|
int dd_in_debugger;
|
|
|
|
int dd_sym_loaded;
|
|
|
|
char *dd_bpt_addr;
|
|
|
|
int dd_bpt_shadow;
|
|
|
|
struct rt_symbol *dd_cc;
|
|
|
|
};
|
|
|
|
.Ed
|
|
|
|
.Pp
|
|
|
|
.Bl -tag -width dd_in_debugger
|
|
|
|
.It Fa dd_version
|
|
|
|
Version number of this interface.
|
|
|
|
.It Fa dd_in_debugger
|
|
|
|
Set by the debugger to indicate to the run-time linker that the program is
|
|
|
|
run under control of a debugger.
|
|
|
|
.It Fa dd_sym_loaded
|
|
|
|
Set by the run-time linker whenever it adds symbols by loading shared objects.
|
|
|
|
.It Fa dd_bpt_addr
|
1996-10-05 18:37:31 +00:00
|
|
|
The address were a breakpoint will be set by the run-time linker to
|
2000-03-02 14:54:02 +00:00
|
|
|
divert control to the debugger.
|
|
|
|
This address is determined by the start-up
|
1994-12-23 22:41:46 +00:00
|
|
|
module,
|
2001-02-01 16:38:02 +00:00
|
|
|
.Pa crt0.o ,
|
1997-01-15 05:33:11 +00:00
|
|
|
to be some convenient place before the call to _main.
|
|
|
|
.It Fa dd_bpt_shadow
|
1994-12-23 22:41:46 +00:00
|
|
|
Contains the original instruction that was at
|
1997-01-15 05:33:11 +00:00
|
|
|
.Fa dd_bpt_addr .
|
1994-12-23 22:41:46 +00:00
|
|
|
The debugger is expected to put this instruction back before continuing the
|
|
|
|
program.
|
|
|
|
.It Fa dd_cc
|
|
|
|
A pointer to the linked list of run-time allocated symbols that the debugger
|
|
|
|
may be interested in.
|
|
|
|
.El
|
|
|
|
.Pp
|
|
|
|
The
|
|
|
|
.Em ld_entry
|
1996-04-08 04:18:31 +00:00
|
|
|
structure defines a set of service routines within
|
|
|
|
.Nm ld.so .
|
|
|
|
.\" See
|
|
|
|
.\" .Xr libdl.a
|
|
|
|
.\" for more information.
|
1994-12-23 22:41:46 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
struct ld_entry {
|
|
|
|
void *(*dlopen)(char *, int);
|
|
|
|
int (*dlclose)(void *);
|
|
|
|
void *(*dlsym)(void *, char *);
|
1995-04-16 12:35:13 +00:00
|
|
|
char *(*dlerror)(void);
|
1994-12-23 22:41:46 +00:00
|
|
|
};
|
|
|
|
.Ed
|
2000-12-29 09:18:45 +00:00
|
|
|
.Pp
|
1994-12-23 22:41:46 +00:00
|
|
|
The
|
|
|
|
.Fa crt_ldso
|
1996-04-08 04:18:31 +00:00
|
|
|
structure defines the interface between the start-up code in crt0 and
|
|
|
|
.Nm ld.so .
|
1994-12-23 22:41:46 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
struct crt_ldso {
|
|
|
|
int crt_ba;
|
|
|
|
int crt_dzfd;
|
|
|
|
int crt_ldfd;
|
|
|
|
struct _dynamic *crt_dp;
|
|
|
|
char **crt_ep;
|
|
|
|
caddr_t crt_bp;
|
|
|
|
char *crt_prog;
|
|
|
|
char *crt_ldso;
|
1995-04-16 12:35:13 +00:00
|
|
|
struct ld_entry *crt_ldentry;
|
1994-12-23 22:41:46 +00:00
|
|
|
};
|
|
|
|
#define CRT_VERSION_SUN 1
|
1995-04-16 12:35:13 +00:00
|
|
|
#define CRT_VERSION_BSD_2 2
|
|
|
|
#define CRT_VERSION_BSD_3 3
|
|
|
|
#define CRT_VERSION_BSD_4 4
|
1994-12-23 22:41:46 +00:00
|
|
|
.Ed
|
|
|
|
.Bl -tag -width crt_dzfd
|
|
|
|
.It Fa crt_ba
|
1996-04-08 04:18:31 +00:00
|
|
|
The virtual address at which
|
|
|
|
.Nm ld.so
|
|
|
|
was loaded by crt0.
|
1994-12-23 22:41:46 +00:00
|
|
|
.It Fa crt_dzfd
|
|
|
|
On SunOS systems, this field contains an open file descriptor to
|
1996-04-08 04:18:31 +00:00
|
|
|
.Dq Pa /dev/zero
|
2000-03-02 14:54:02 +00:00
|
|
|
used to get demand paged zeroed pages.
|
|
|
|
On
|
2000-11-14 11:20:58 +00:00
|
|
|
.Fx
|
1997-03-21 20:14:15 +00:00
|
|
|
systems it contains -1.
|
1994-12-23 22:41:46 +00:00
|
|
|
.It Fa crt_ldfd
|
1996-04-08 04:18:31 +00:00
|
|
|
Contains an open file descriptor that was used by crt0 to load
|
|
|
|
.Nm ld.so .
|
1994-12-23 22:41:46 +00:00
|
|
|
.It Fa crt_dp
|
|
|
|
A pointer to main's
|
|
|
|
.Fa _dynamic
|
|
|
|
structure.
|
|
|
|
.It Fa crt_ep
|
|
|
|
A pointer to the environment strings.
|
|
|
|
.It Fa crt_bp
|
|
|
|
The address at which a breakpoint will be placed by the run-time linker
|
|
|
|
if the main program is run by a debugger.
|
|
|
|
See
|
|
|
|
.Fa so_debug
|
|
|
|
.It Fa crt_prog
|
|
|
|
The name of the main program as determined by crt0 (CRT_VERSION_BSD3 only).
|
|
|
|
.It Fa crt_ldso
|
|
|
|
The path of the run-time linker as mapped by crt0 (CRT_VERSION_BSD4 only).
|
|
|
|
.El
|
|
|
|
.Pp
|
|
|
|
The
|
|
|
|
.Fa hints_header
|
|
|
|
and
|
|
|
|
.Fa hints_bucket
|
|
|
|
structures define the layout of the library hints, normally found in
|
1996-04-08 04:18:31 +00:00
|
|
|
.Dq Pa /var/run/ld.so.hints ,
|
|
|
|
which is used by
|
|
|
|
.Nm ld.so
|
|
|
|
to quickly locate the shared object images in the
|
1994-12-23 22:41:46 +00:00
|
|
|
filesystem.
|
|
|
|
The organization of the hints file is not unlike that of an
|
|
|
|
.Dq a.out
|
|
|
|
object file, in that it contains a header determining the offset and size
|
|
|
|
of a table of fixed sized hash buckets and a common string pool.
|
|
|
|
.Bd -literal -offset indent
|
|
|
|
struct hints_header {
|
|
|
|
long hh_magic;
|
|
|
|
#define HH_MAGIC 011421044151
|
|
|
|
long hh_version;
|
|
|
|
#define LD_HINTS_VERSION_1 1
|
|
|
|
long hh_hashtab;
|
|
|
|
long hh_nbucket;
|
|
|
|
long hh_strtab;
|
|
|
|
long hh_strtab_sz;
|
|
|
|
long hh_ehints;
|
|
|
|
};
|
|
|
|
.Ed
|
|
|
|
.Bl -tag -width hh_strtab_sz
|
|
|
|
.It Fa hh_magic
|
|
|
|
Hints file magic number.
|
|
|
|
.It Fa hh_version
|
|
|
|
Interface version number.
|
|
|
|
.It Fa hh_hashtab
|
|
|
|
Offset of hash table.
|
|
|
|
.It Fa hh_strtab
|
|
|
|
Offset of string table.
|
|
|
|
.It Fa hh_strtab_sz
|
|
|
|
Size of strings.
|
|
|
|
.It Fa hh_ehints
|
|
|
|
Maximum usable offset in hints file.
|
|
|
|
.El
|
|
|
|
.Pp
|
|
|
|
.Bd -literal -offset indent
|
|
|
|
/*
|
|
|
|
* Hash table element in hints file.
|
|
|
|
*/
|
|
|
|
struct hints_bucket {
|
|
|
|
int hi_namex;
|
|
|
|
int hi_pathx;
|
|
|
|
int hi_dewey[MAXDEWEY];
|
|
|
|
int hi_ndewey;
|
|
|
|
#define hi_major hi_dewey[0]
|
|
|
|
#define hi_minor hi_dewey[1]
|
|
|
|
int hi_next;
|
|
|
|
};
|
|
|
|
.Ed
|
|
|
|
.Bl -tag -width hi_ndewey
|
|
|
|
.It Fa hi_namex
|
|
|
|
Index of the string identifying the library.
|
|
|
|
.It Fa hi_pathx
|
|
|
|
Index of the string representing the full path name of the library.
|
|
|
|
.It Fa hi_dewey
|
|
|
|
The version numbers of the shared library.
|
|
|
|
.It Fa hi_ndewey
|
|
|
|
The number of valid entries in
|
1997-01-15 05:33:11 +00:00
|
|
|
.Fa hi_dewey .
|
1994-12-23 22:41:46 +00:00
|
|
|
.It Fa hi_next
|
|
|
|
Next bucket in case of hashing collisions.
|
|
|
|
.El
|
|
|
|
.Sh CAVEATS
|
|
|
|
Only the (GNU) C compiler currently supports the creation of shared libraries.
|
|
|
|
Other programming languages can not be used.
|