.\" This is in the public domain
.\" %%%LICENSE_END
.\"
-.TH LD.SO 8 2017-09-15 "GNU" "Linux Programmer's Manual"
+.TH LD.SO 8 2019-02-27 "GNU" "Linux Programmer's Manual"
.SH NAME
ld.so, ld\-linux.so \- dynamic linker/loader
.SH SYNOPSIS
.PP
The program
.B ld.so
-handles a.out binaries, a format used long ago;
+handles a.out binaries, a binary format used long ago.
+The program
.B ld\-linux.so*
(\fI/lib/ld\-linux.so.1\fP for libc5, \fI/lib/ld\-linux.so.2\fP for glibc2)
-handles ELF,
-which everybody has been using for years now.
-Otherwise, both have the same behavior, and use the same
-support files and programs as
-.BR ldd (1),
+handles binaries that are in the more modern ELF format.
+Both programs have the same behavior, and use the same
+support files and programs
+.RB ( ldd (1),
.BR ldconfig (8),
and
-.IR /etc/ld.so.conf .
+.IR /etc/ld.so.conf ).
.PP
When resolving shared object dependencies,
the dynamic linker first inspects each dependency
.\" Don't do this!!
.SH OPTIONS
.TP
-.B \-\-list
-List all dependencies and how they are resolved.
-.TP
-.B \-\-verify
-Verify that program is dynamically linked and this dynamic linker can handle
-it.
+.BI \-\-audit " list"
+Use objects named in
+.I list
+as auditors.
+The objects in
+.I list
+are delimited by colons.
.TP
.B \-\-inhibit\-cache
Do not use
Ignore RPATH and RUNPATH information in object names in
.IR list .
This option is ignored when running in secure-execution mode (see below).
+The objects in
+.I list
+are delimited by colons or spaces.
.TP
-.BI \-\-audit " list"
-Use objects named in
+.B \-\-list
+List all dependencies and how they are resolved.
+.TP
+.BR \-\-preload " \fIlist\fP (since glibc 2.30)"
+Preload the objects specified in
+.IR list .
+The objects in
.I list
-as auditors.
+are delimited by colons or spaces.
+The objects are preloaded as explained in the description of the
+.BR LD_PRELOAD
+environment variable below.
+.IP
+By contrast with
+.BR LD_PRELOAD ,
+the
+.BR \-\-preload
+option provides a way to perform preloading for a single executable
+without affecting preloading performed in any child process that executes
+a new program.
+.TP
+.B \-\-verify
+Verify that program is dynamically linked and this dynamic linker can handle
+it.
.SH ENVIRONMENT
Various environment variables influence the operation of the dynamic linker.
.\"
.SS Secure-execution mode
For security reasons,
-the effects of some environment variables are voided or modified if
-the dynamic linker determines that the binary should be
-run in secure-execution mode.
-(For details, see the discussion of individual environment variables below.)
+if the dynamic linker determines that a binary should be
+run in secure-execution mode,
+the effects of some environment variables are voided or modified,
+and furthermore those environment variables are stripped from the environment,
+so that the program does not even see the definitions.
+Some of these environment variables affect the operation of
+the dynamic linker itself, and are described below.
+Other environment variables treated in this way include:
+.BR GCONV_PATH ,
+.BR GETCONF_DIR ,
+.BR HOSTALIASES ,
+.BR LOCALDOMAIN ,
+.BR LOCPATH ,
+.BR MALLOC_TRACE ,
+.BR NIS_PATH ,
+.BR NLSPATH ,
+.BR RESOLV_HOST_CONF ,
+.BR RES_OPTIONS ,
+.BR TMPDIR ,
+and
+.BR TZDIR .
+.PP
A binary is executed in secure-execution mode if the
.B AT_SECURE
entry in the auxiliary vector (see
.B LD_PRELOAD
A list of additional, user-specified, ELF shared
objects to be loaded before all others.
+This feature can be used to selectively override functions
+in other shared objects.
+.IP
The items of the list can be separated by spaces or colons,
and there is no support for escaping either separator.
-This can be used to selectively override functions in other shared objects.
The objects are searched for using the rules given under DESCRIPTION.
+Objects are searched for and added to the link map in the left-to-right
+order specified in the list.
.IP
In secure-execution mode,
preload pathnames containing slashes are ignored.
.\"
.\" which will preload the libmod.so in 'lib' or 'lib64', using it
.\" in preference to the version in '.'.
+.IP
+There are various methods of specifying libraries to be preloaded,
+and these are handled in the following order:
+.RS
+.IP (1) 4
+The
+.BR LD_PRELOAD
+environment variable.
+.IP (2)
+The
+.B \-\-preload
+command-line option when invoking the dynamic linker directly.
+.IP (3)
+The
+.I /etc/ld.so.preload
+file (described below).
+.RE
.TP
.BR LD_TRACE_LOADED_OBJECTS
If set (to any value), causes the program to list its dynamic
many obsolete or only for internal use.
.TP
.BR LD_AUDIT " (since glibc 2.4)"
-A colon-separated list of user-specified, ELF shared objects
+A list of user-specified, ELF shared objects
to be loaded before all others in a separate linker namespace
(i.e., one that does not intrude upon the normal symbol bindings that
would occur in the process)
-and there is no support for escaping the separator.
These objects can be used to audit the operation of the dynamic linker.
+The items in the list are colon-separated,
+and there is no support for escaping the separator.
.IP
.B LD_AUDIT
is ignored in secure-execution mode.
Hardware capability directories can be cascaded to combine CPU features.
The list of supported hardware capability names depends on the CPU.
The following names are currently recognized:
+.\" Presumably, this info comes from sysdeps/i386/dl-procinfo.c and
+.\" similar files
.TP
.B Alpha
ev4, ev5, ev56, ev6, ev67
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