\input texinfo
@setfilename ld.info
@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-@c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
+@c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
@c Free Software Foundation, Inc.
@syncodeindex ky cp
@c man begin INCLUDE
@item common-page-size=@var{value}
Set the emulation common page size to @var{value}.
+@item stack-size=@var{value}
+Specify a stack size for in an ELF @code{PT_GNU_STACK} segment.
+Specifying zero will override any default non-zero sized
+@code{PT_GNU_STACK} segment creation.
+
@end table
Other keywords are ignored for Solaris compatibility.
@itemx --no-copy-dt-needed-entries
This option affects the treatment of dynamic libraries referred to
by DT_NEEDED tags @emph{inside} ELF dynamic libraries mentioned on the
-command line. Normally the linker will add a DT_NEEDED tag to the
+command line. Normally the linker won't add a DT_NEEDED tag to the
output binary for each library mentioned in a DT_NEEDED tag in an
-input dynamic library. With @option{--no-copy-dt-needed-entries}
+input dynamic library. With @option{--copy-dt-needed-entries}
specified on the command line however any dynamic libraries that
-follow it will have their DT_NEEDED entries ignored. The default
-behaviour can be restored with @option{--copy-dt-needed-entries}.
+follow it will have their DT_NEEDED entries added. The default
+behaviour can be restored with @option{--no-copy-dt-needed-entries}.
This option also has an effect on the resolution of symbols in dynamic
-libraries. With the default setting dynamic libraries mentioned on
-the command line will be recursively searched, following their
-DT_NEEDED tags to other libraries, in order to resolve symbols
-required by the output binary. With
-@option{--no-copy-dt-needed-entries} specified however the searching
-of dynamic libraries that follow it will stop with the dynamic
-library itself. No DT_NEEDED links will be traversed to resolve
+libraries. With @option{--copy-dt-needed-entries} dynamic libraries
+mentioned on the command line will be recursively searched, following
+their DT_NEEDED tags to other libraries, in order to resolve symbols
+required by the output binary. With the default setting however
+the searching of dynamic libraries that follow it will stop with the
+dynamic library itself. No DT_NEEDED links will be traversed to resolve
symbols.
@cindex cross reference table
@menu
* Simple Assignments:: Simple Assignments
+* HIDDEN:: HIDDEN
* PROVIDE:: PROVIDE
* PROVIDE_HIDDEN:: PROVIDE_HIDDEN
* Source Code Reference:: How to use a linker script defined symbol in source code
defined as the address following the @samp{.text} output section aligned
upward to a 4 byte boundary.
+@node HIDDEN
+@subsection HIDDEN
+@cindex HIDDEN
+For ELF targeted ports, define a symbol that will be hidden and won't be
+exported. The syntax is @code{HIDDEN(@var{symbol} = @var{expression})}.
+
+Here is the example from @ref{Simple Assignments}, rewritten to use
+@code{HIDDEN}:
+
+@smallexample
+HIDDEN(floating_point = 0);
+SECTIONS
+@{
+ .text :
+ @{
+ *(.text)
+ HIDDEN(_etext = .);
+ @}
+ HIDDEN(_bdata = (. + 3) & ~ 3);
+ .data : @{ *(.data) @}
+@}
+@end smallexample
+@noindent
+In this case none of the three symbols will be visible outside this module.
+
@node PROVIDE
@subsection PROVIDE
@cindex PROVIDE
If the section sorting command in linker script is nested, the
command line option will be ignored.
+@cindex SORT_NONE
+@code{SORT_NONE} disables section sorting by ignoring the command line
+section sorting option.
+
If you ever get confused about where input sections are going, use the
@samp{-M} linker option to generate a map file. The map file shows
precisely how input sections are mapped to output sections.
If an orphaned section's name is representable as a C identifier then
the linker will automatically @pxref{PROVIDE} two symbols:
-__start_SECNAME and __end_SECNAME, where SECNAME is the name of the
+__start_SECNAME and __stop_SECNAME, where SECNAME is the name of the
section. These indicate the start address and end address of the
orphaned section respectively. Note: most section names are not
representable as C identifiers because they contain a @samp{.}
@itemize @bullet
@item
+Unary operations on an absolute address or number, and binary
+operations on two absolute addresses or two numbers, or between one
+absolute address and a number, apply the operator to the value(s).
+@item
Unary operations on a relative address, and binary operations on two
relative addresses in the same section or between one relative address
and a number, apply the operator to the offset part of the address(es).
@item
-Unary operations on an absolute address, and binary operations on one
-or more absolute addresses or on two relative addresses not in the
-same section, first convert any non-absolute term to an absolute
-address before applying the operator.
+Other binary operations, that is, between two relative addresses not
+in the same section, or between a relative address and an absolute
+address, first convert any non-absolute term to an absolute address
+before applying the operator.
@end itemize
The result section of each sub-expression is as follows:
the veneer. The extra cycles required to call and return from the veneer
are sufficient to avoid the erratum in both the scalar and vector cases.
+@cindex ARM1176 erratum workaround
+@kindex --fix-arm1176
+@kindex --no-fix-arm1176
+The @samp{--fix-arm1176} switch enables a link-time workaround for an erratum
+in certain ARM1176 processors. The workaround is enabled by default if you
+are targetting ARM v6 (excluding ARM v6T2) or earlier. It can be disabled
+unconditionally by specifying @samp{--no-fix-arm1176}.
+
+Further information is available in the ``ARM1176JZ-S and ARM1176JZF-S
+Programmer Advice Notice'' available on the ARM documentaion website at:
+http://infocenter.arm.com/.
+
@cindex NO_ENUM_SIZE_WARNING
@kindex --no-enum-size-warning
The @option{--no-enum-size-warning} switch prevents the linker from
@cindex PowerPC64 multi-TOC
@kindex --no-multi-toc
@item --no-multi-toc
-By default, PowerPC64 GCC generates code for a TOC model where TOC
+If given any toc option besides @code{-mcmodel=medium} or
+@code{-mcmodel=large}, PowerPC64 GCC generates code for a TOC model
+where TOC
entries are accessed with a 16-bit offset from r2. This limits the
total TOC size to 64K. PowerPC64 @command{ld} extends this limit by
grouping code sections such that each group uses less than 64K for its
help if a single input file has a @code{.toc} section that exceeds
64K, most likely from linking multiple files with @command{ld -r}.
Use this option to turn off this feature.
+
+@cindex PowerPC64 TOC sorting
+@kindex --no-toc-sort
+@item --no-toc-sort
+By default, @command{ld} sorts TOC sections so that those whose file
+happens to have a section called @code{.init} or @code{.fini} are
+placed first, followed by TOC sections referenced by code generated
+with PowerPC64 gcc's @code{-mcmodel=small}, and lastly TOC sections
+referenced only by code generated with PowerPC64 gcc's
+@code{-mcmodel=medium} or @code{-mcmodel=large} options. Doing this
+results in better TOC grouping for multi-TOC. Use this option to turn
+off this feature.
+
+@cindex PowerPC64 PLT stub alignment
+@kindex --plt-align
+@kindex --no-plt-align
+@item --plt-align
+@itemx --no-plt-align
+Use these options to control whether individual PLT call stubs are
+aligned to a 32-byte boundary, or to the specified power of two
+boundary when using @code{--plt-align=}. By default PLT call stubs
+are packed tightly.
+
+@cindex PowerPC64 PLT call stub static chain
+@kindex --plt-static-chain
+@kindex --no-plt-static-chain
+@item --plt-static-chain
+@itemx --no-plt-static-chain
+Use these options to control whether PLT call stubs load the static
+chain pointer (r11). @code{ld} defaults to not loading the static
+chain since there is never any need to do so on a PLT call.
+
+@cindex PowerPC64 PLT call stub thread safety
+@kindex --plt-thread-safe
+@kindex --no-plt-thread-safe
+@item --plt-thread-safe
+@itemx --no-thread-safe
+With power7's weakly ordered memory model, it is possible when using
+lazy binding for ld.so to update a plt entry in one thread and have
+another thread see the individual plt entry words update in the wrong
+order, despite ld.so carefully writing in the correct order and using
+memory write barriers. To avoid this we need some sort of read
+barrier in the call stub, or use LD_BIND_NOW=1. By default, @code{ld}
+looks for calls to commonly used functions that create threads, and if
+seen, adds the necessary barriers. Use these options to change the
+default behaviour.
@end table
@ifclear GENERIC