\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
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1991-2014 Free Software Foundation, Inc.
@syncodeindex ky cp
@c man begin INCLUDE
@include configdoc.texi
@set UsesEnvVars
@set GENERIC
@set ARM
+@set C6X
@set H8300
@set HPPA
@set I960
@set M68HC11
@set M68K
+@set MIPS
@set MMIX
@set MSP430
+@set NDS32
+@set NIOSII
@set POWERPC
@set POWERPC64
@set Renesas
@end ifset
version @value{VERSION}.
-Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+Copyright @copyright{} 1991-2014 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
@vskip 0pt plus 1filll
@c man begin COPYRIGHT
-Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free
-Software Foundation, Inc.
+Copyright @copyright{} 1991-2014 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
@ifset ARM
* ARM:: ld and the ARM family
@end ifset
-@ifset HPPA
-* HPPA ELF32:: ld and HPPA 32-bit ELF
-@end ifset
@ifset M68HC11
* M68HC11/68HC12:: ld and the Motorola 68HC11 and 68HC12 families
@end ifset
+@ifset HPPA
+* HPPA ELF32:: ld and HPPA 32-bit ELF
+@end ifset
@ifset M68K
* M68K:: ld and Motorola 68K family
@end ifset
+@ifset MIPS
+* MIPS:: ld and MIPS family
+@end ifset
@ifset POWERPC
* PowerPC ELF32:: ld and PowerPC 32-bit ELF Support
@end ifset
specified in the library. If specified multiple times @code{DT_AUDIT}
will contain a colon separated list of audit interfaces to use. If the linker
finds an object with an audit entry while searching for shared libraries,
-it will add a corresponding @code{DT_DEPAUDIT} entry in the output file.
+it will add a corresponding @code{DT_DEPAUDIT} entry in the output file.
This option is only meaningful on ELF platforms supporting the rtld-audit
-interface.
+interface.
@ifset I960
@cindex architectures
specified in the library. If specified multiple times @code{DT_DEPAUDIT}
will contain a colon separated list of audit interfaces to use. This
option is only meaningful on ELF platforms supporting the rtld-audit interface.
-The -P option is provided for Solaris compatibility.
+The -P option is provided for Solaris compatibility.
@cindex entry point, from command line
@kindex -e @var{entry}
@itemx --gpsize=@var{value}
Set the maximum size of objects to be optimized using the GP register to
@var{size}. This is only meaningful for object file formats such as
-MIPS ECOFF which supports putting large and small objects into different
+MIPS ELF that support putting large and small objects into different
sections. This is ignored for other object file formats.
@cindex runtime library name
option is specified.
If @var{searchdir} begins with @code{=}, then the @code{=} will be replaced
-by the @dfn{sysroot prefix}, a path specified when the linker is configured.
+by the @dfn{sysroot prefix}, controlled by the @samp{--sysroot} option, or
+specified when the linker is configured.
@ifset UsesEnvVars
The default set of paths searched (without being specified with
no difference in the linker's behaviour for different non-zero values
of this option. Again this may change with future releases.
+@kindex --push-state
+@cindex push state governing input file handling
+@item --push-state
+The @option{--push-state} allows to preserve the current state of the
+flags which govern the input file handling so that they can all be
+restored with one corresponding @option{--pop-state} option.
+
+The option which are covered are: @option{-Bdynamic}, @option{-Bstatic},
+@option{-dn}, @option{-dy}, @option{-call_shared}, @option{-non_shared},
+@option{-static}, @option{-N}, @option{-n}, @option{--whole-archive},
+@option{--no-whole-archive}, @option{-r}, @option{-Ur},
+@option{--copy-dt-needed-entries}, @option{--no-copy-dt-needed-entries},
+@option{--as-needed}, @option{--no-as-needed}, and @option{-a}.
+
+One target for this option are specifications for @file{pkg-config}. When
+used with the @option{--libs} option all possibly needed libraries are
+listed and then possibly linked with all the time. It is better to return
+something as follows:
+
+@smallexample
+-Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state
+@end smallexample
+
+@kindex --pop-state
+@cindex pop state governing input file handling
+Undoes the effect of --push-state, restores the previous values of the
+flags governing input file handling.
+
@kindex -q
@kindex --emit-relocs
@cindex retain relocations in final executable
@item execstack
Marks the object as requiring executable stack.
+@item global
+This option is only meaningful when building a shared object. It makes
+the symbols defined by this shared object available for symbol resolution
+of subsequently loaded libraries.
+
@item initfirst
This option is only meaningful when building a shared object.
It marks the object so that its runtime initialization will occur
@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.
+
+@item bndplt
+Always generate BND prefix in PLT entries. Supported for Linux/x86_64.
+
@end table
Other keywords are ignored for Solaris compatibility.
the linker will add a DT_NEEDED tag for each dynamic library mentioned
on the command line, regardless of whether the library is actually
needed or not. @option{--as-needed} causes a DT_NEEDED tag to only be
-emitted for a library that satisfies an undefined symbol reference
-from a regular object file or, if the library is not found in the
-DT_NEEDED lists of other libraries linked up to that point, an
-undefined symbol reference from another dynamic library.
-@option{--no-as-needed} restores the default behaviour.
+emitted for a library that @emph{at that point in the link} satisfies a
+non-weak undefined symbol reference from a regular object file or, if
+the library is not found in the DT_NEEDED lists of other needed libraries, a
+non-weak undefined symbol reference from another needed dynamic library.
+Object files or libraries appearing on the command line @emph{after}
+the library in question do not affect whether the library is seen as
+needed. This is similar to the rules for extraction of object files
+from archives. @option{--no-as-needed} restores the default behaviour.
@kindex --add-needed
@kindex --no-add-needed
@kindex --no-copy-dt-needed-entries
@item --copy-dt-needed-entries
@itemx --no-copy-dt-needed-entries
-This option affects the treatment of dynamic libraries referred to
+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
easily processed by a script if necessary. The symbols are printed out,
sorted by name. For each symbol, a list of file names is given. If the
symbol is defined, the first file listed is the location of the
-definition. The remaining files contain references to the symbol.
+definition. If the symbol is defined as a common value then any files
+where this happens appear next. Finally any files that reference the
+symbol are listed.
@cindex common allocation
@kindex --no-define-common
relocations. See @samp{--entry} and @samp{--undefined}.
This option can be set when doing a partial link (enabled with option
-@samp{-r}). In this case the root of symbols kept must be explicitly
+@samp{-r}). In this case the root of symbols kept must be explicitly
specified either by an @samp{--entry} or @samp{--undefined} option or by
a @code{ENTRY} command in the linker script.
be restored by specifying @samp{--no-print-gc-sections} on the command
line.
+@kindex --print-output-format
+@cindex output format
+@item --print-output-format
+Print the name of the default output format (perhaps influenced by
+other command-line options). This is the string that would appear
+in an @code{OUTPUT_FORMAT} linker script command (@pxref{File Commands}).
+
@cindex help
@cindex usage
@kindex --help
@ifset M68HC11
@xref{M68HC11/68HC12,,@command{ld} and the 68HC11 and 68HC12}.
@end ifset
+@ifset NIOSII
+@xref{Nios II,,@command{ld} and the Altera Nios II}.
+@end ifset
@ifset POWERPC
@xref{PowerPC ELF32,,@command{ld} and PowerPC 32-bit ELF Support}.
@end ifset
global optimizations that become possible when the linker resolves
addressing in the program, such as relaxing address modes,
synthesizing new instructions, selecting shorter version of current
-instructions, and combinig constant values.
+instructions, and combining constant values.
On some platforms these link time global optimizations may make symbolic
debugging of the resulting executable impossible.
On SunOS, if the @option{-rpath} option was not used, search any
directories specified using @option{-L} options.
@item
-For a native linker, the search the contents of the environment
+For a native linker, search the contents of the environment
variable @code{LD_LIBRARY_PATH}.
@item
For a native ELF linker, the directories in @code{DT_RUNPATH} or
@kindex -Ttext-segment=@var{org}
@item -Ttext-segment=@var{org}
@cindex text segment origin, cmd line
-When creating an ELF executable or shared object, it will set the address
-of the first byte of the text segment.
+When creating an ELF executable, it will set the address of the first
+byte of the text segment.
+
+@kindex -Trodata-segment=@var{org}
+@item -Trodata-segment=@var{org}
+@cindex rodata segment origin, cmd line
+When creating an ELF executable or shared object for a target where
+the read-only data is in its own segment separate from the executable
+text, it will set the address of the first byte of the read-only data segment.
+
+@kindex -Tldata-segment=@var{org}
+@item -Tldata-segment=@var{org}
+@cindex ldata segment origin, cmd line
+When creating an ELF executable or shared object for x86-64 medium memory
+model, it will set the address of the first byte of the ldata segment.
@kindex --unresolved-symbols
@item --unresolved-symbols=@var{method}
unresolved symbol but the option @option{--warn-unresolved-symbols}
can change this to a warning.
-@kindex --verbose
-@cindex verbose
+@kindex --verbose[=@var{NUMBER}]
+@cindex verbose[=@var{NUMBER}]
@item --dll-verbose
-@itemx --verbose
+@itemx --verbose[=@var{NUMBER}]
Display the version number for @command{ld} and list the linker emulations
supported. Display which input files can and cannot be opened. Display
-the linker script being used by the linker.
+the linker script being used by the linker. If the optional @var{NUMBER}
+argument > 1, plugin symbol status will also be displayed.
@kindex --version-script=@var{version-scriptfile}
@cindex version script, symbol versions
@cindex combining symbols, warnings on
@item --warn-common
Warn when a common symbol is combined with another common symbol or with
-a symbol definition. Unix linkers allow this somewhat sloppy practise,
+a symbol definition. Unix linkers allow this somewhat sloppy practice,
but linkers on some other operating systems do not. This option allows
you to find potential problems from combining global symbols.
-Unfortunately, some C libraries use this practise, so you may get some
+Unfortunately, some C libraries use this practice, so you may get some
warnings about symbols in the libraries as well as in your programs.
There are three kinds of global symbols, illustrated here by C examples:
Request creation of @code{.eh_frame_hdr} section and ELF
@code{PT_GNU_EH_FRAME} segment header.
+@kindex --ld-generated-unwind-info
+@item --no-ld-generated-unwind-info
+Request creation of @code{.eh_frame} unwind info for linker
+generated code sections like PLT. This option is on by default
+if linker generated unwind info is supported.
+
@kindex --enable-new-dtags
@kindex --disable-new-dtags
@item --enable-new-dtags
@itemx --disable-new-dtags
This linker can create the new dynamic tags in ELF. But the older ELF
systems may not understand them. If you specify
-@option{--enable-new-dtags}, the dynamic tags will be created as needed.
+@option{--enable-new-dtags}, the new dynamic tags will be created as needed
+and older dynamic tags will be omitted.
If you specify @option{--disable-new-dtags}, no new dynamic tags will be
-created. By default, the new dynamic tags are not created. Note that
+created. By default, the new dynamic tags are created. Note that
those options are only available for ELF systems.
@kindex --hash-size=@var{number}
@kindex --build-id=@var{style}
@item --build-id
@itemx --build-id=@var{style}
-Request creation of @code{.note.gnu.build-id} ELF note section.
-The contents of the note are unique bits identifying this linked
-file. @var{style} can be @code{uuid} to use 128 random bits,
-@code{sha1} to use a 160-bit @sc{SHA1} hash on the normative
-parts of the output contents, @code{md5} to use a 128-bit
-@sc{MD5} hash on the normative parts of the output contents, or
-@code{0x@var{hexstring}} to use a chosen bit string specified as
-an even number of hexadecimal digits (@code{-} and @code{:}
-characters between digit pairs are ignored). If @var{style} is
-omitted, @code{sha1} is used.
+Request the creation of a @code{.note.gnu.build-id} ELF note section
+or a @code{.build-id} COFF section. The contents of the note are
+unique bits identifying this linked file. @var{style} can be
+@code{uuid} to use 128 random bits, @code{sha1} to use a 160-bit
+@sc{SHA1} hash on the normative parts of the output contents,
+@code{md5} to use a 128-bit @sc{MD5} hash on the normative parts of
+the output contents, or @code{0x@var{hexstring}} to use a chosen bit
+string specified as an even number of hexadecimal digits (@code{-} and
+@code{:} characters between digit pairs are ignored). If @var{style}
+is omitted, @code{sha1} is used.
The @code{md5} and @code{sha1} styles produces an identifier
that is always the same in an identical output file, but will be
disallow it in object files, by using these two options. Executable images
generated with these long section names are slightly non-standard, carrying
as they do a string table, and may generate confusing output when examined
-with non-GNU PE-aware tools, such as file viewers and dumpers. However,
-GDB relies on the use of PE long section names to find Dwarf-2 debug
+with non-GNU PE-aware tools, such as file viewers and dumpers. However,
+GDB relies on the use of PE long section names to find Dwarf-2 debug
information sections in an executable image at runtime, and so if neither
option is specified on the command-line, @command{ld} will enable long
section names, overriding the default and technically correct behaviour,
@item --heap @var{reserve}
@itemx --heap @var{reserve},@var{commit}
Specify the number of bytes of memory to reserve (and optionally commit)
-to be used as heap for this program. The default is 1Mb reserved, 4K
+to be used as heap for this program. The default is 1MB reserved, 4K
committed.
[This option is specific to the i386 PE targeted port of the linker]
section of the BOOT.INI. Otherwise, this bit has no effect.
[This option is specific to PE targeted ports of the linker]
+@kindex --disable-large-address-aware
+@item --disable-large-address-aware
+Reverts the effect of a previous @samp{--large-address-aware} option.
+This is useful if @samp{--large-address-aware} is always set by the compiler
+driver (e.g. Cygwin gcc) and the executable does not support virtual
+addresses greater than 2 gigabytes.
+[This option is specific to PE targeted ports of the linker]
+
@kindex --major-image-version
@item --major-image-version @var{value}
Sets the major number of the ``image version''. Defaults to 1.
@kindex --enable-auto-image-base
@item --enable-auto-image-base
-Automatically choose the image base for DLLs, unless one is specified
-using the @code{--image-base} argument. By using a hash generated
-from the dllname to create unique image bases for each DLL, in-memory
-collisions and relocations which can delay program execution are
-avoided.
+@itemx --enable-auto-image-base=@var{value}
+Automatically choose the image base for DLLs, optionally starting with base
+@var{value}, unless one is specified using the @code{--image-base} argument.
+By using a hash generated from the dllname to create unique image bases
+for each DLL, in-memory collisions and relocations which can delay program
+execution are avoided.
[This option is specific to the i386 PE targeted port of the linker]
@kindex --disable-auto-image-base
A third method of dealing with this difficulty is to abandon
'auto-import' for the offending symbol and mark it with
-@code{__declspec(dllimport)}. However, in practise that
+@code{__declspec(dllimport)}. However, in practice that
requires using compile-time #defines to indicate whether you are
building a DLL, building client code that will link to the DLL, or
merely building/linking to a static library. In making the choice
@kindex --disable-runtime-pseudo-reloc
@item --disable-runtime-pseudo-reloc
Do not create pseudo relocations for non-zero offset DATA imports from
-DLLs. This is the default.
+DLLs.
[This option is specific to the i386 PE targeted port of the linker]
@kindex --enable-extra-pe-debug
@item --stack @var{reserve}
@itemx --stack @var{reserve},@var{commit}
Specify the number of bytes of memory to reserve (and optionally commit)
-to be used as stack for this program. The default is 2Mb reserved, 4K
+to be used as stack for this program. The default is 2MB reserved, 4K
committed.
[This option is specific to the i386 PE targeted port of the linker]
of the PE file header:
[These options are specific to PE targeted ports of the linker]
+@kindex --high-entropy-va
+@item --high-entropy-va
+Image is compatible with 64-bit address space layout randomization
+(ASLR).
+
@kindex --dynamicbase
@item --dynamicbase
The image base address may be relocated using address space layout
@kindex --wdmdriver
@item --wdmdriver
The driver uses the MS Windows Driver Model.
-
+
@kindex --tsaware
@item --tsaware
The image is Terminal Server aware.
+@kindex --insert-timestamp
+@item --insert-timestamp
+@itemx --no-insert-timestamp
+Insert a real timestamp into the image. This is the default behaviour
+as it matches legacy code and it means that the image will work with
+other, proprietary tools. The problem with this default is that it
+will result in slightly different images being produced each tiem the
+same sources are linked. The option @option{--no-insert-timestamp}
+can be used to insert a zero value for the timestamp, this ensuring
+that binaries produced from indentical sources will compare
+identically.
@end table
@c man end
+@ifset C6X
+@subsection Options specific to C6X uClinux targets
+
+@c man begin OPTIONS
+
+The C6X uClinux target uses a binary format called DSBT to support shared
+libraries. Each shared library in the system needs to have a unique index;
+all executables use an index of 0.
+
+@table @gcctabopt
+
+@kindex --dsbt-size
+@item --dsbt-size @var{size}
+This option sets the number of entires in the DSBT of the current executable
+or shared library to @var{size}. The default is to create a table with 64
+entries.
+
+@kindex --dsbt-index
+@item --dsbt-index @var{index}
+This option sets the DSBT index of the current executable or shared library
+to @var{index}. The default is 0, which is appropriate for generating
+executables. If a shared library is generated with a DSBT index of 0, the
+@code{R_C6000_DSBT_INDEX} relocs are copied into the output file.
+
+@kindex --no-merge-exidx-entries
+The @samp{--no-merge-exidx-entries} switch disables the merging of adjacent
+exidx entries in frame unwind info.
+
+@end table
+
+@c man end
+@end ifset
+
@ifset M68HC11
@subsection Options specific to Motorola 68HC11 and 68HC12 targets
@c man end
@end ifset
+@ifset MIPS
+@subsection Options specific to MIPS targets
+
+@c man begin OPTIONS
+
+The following options are supported to control microMIPS instruction
+generation when linking for MIPS targets.
+
+@table @gcctabopt
+
+@kindex --insn32
+@item --insn32
+@kindex --no-insn32
+@itemx --no-insn32
+These options control the choice of microMIPS instructions used in code
+generated by the linker, such as that in the PLT or lazy binding stubs,
+or in relaxation. If @samp{--insn32} is used, then the linker only uses
+32-bit instruction encodings. By default or if @samp{--no-insn32} is
+used, all instruction encodings are used, including 16-bit ones where
+possible.
+
+@end table
+
+@c man end
+@end ifset
+
@ifset UsesEnvVars
@node Environment
@section Environment Variables
Each section in an object file has a name and a size. Most sections
also have an associated block of data, known as the @dfn{section
-contents}. A section may be marked as @dfn{loadable}, which mean that
+contents}. A section may be marked as @dfn{loadable}, which means that
the contents should be loaded into memory when the output file is run.
A section with no contents may be @dfn{allocatable}, which means that an
area in memory should be set aside, but nothing in particular should be
located inside the @dfn{sysroot prefix}, the filename will be looked
for in the @dfn{sysroot prefix}. Otherwise, the linker will try to
open the file in the current directory. If it is not found, the
-linker will search through the archive library search path. See the
+linker will search through the archive library search path.
+The @dfn{sysroot prefix} can also be forced by specifying @code{=}
+as the first character in the filename path. See also the
description of @samp{-L} in @ref{Options,,Command Line Options}.
If you use @samp{INPUT (-l@var{file})}, @command{ld} will transform the
@code{C}:
@multitable @columnfractions .25 .25 .25 .25
@item Section @tab Variant A @tab Variant B @tab Variant C
-@item .text @tab RAM @tab ROM @tab ROM
+@item .text @tab RAM @tab ROM @tab ROM
@item .rodata @tab RAM @tab ROM @tab ROM2
@item .data @tab RAM @tab RAM/ROM @tab RAM/ROM2
@item .bss @tab RAM @tab RAM @tab RAM
architecture of an object file by using the @code{objdump} program with
the @samp{-f} option.
@end ifclear
+
+@item LD_FEATURE(@var{string})
+@kindex LD_FEATURE(@var{string})
+This command may be used to modify @command{ld} behavior. If
+@var{string} is @code{"SANE_EXPR"} then absolute symbols and numbers
+in a script are simply treated as numbers everywhere.
+@xref{Expression Section}.
@end table
@node Assignments
@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
int foo = 1000;
@end smallexample
-creates a entry called @samp{foo} in the symbol table. This entry
+creates an entry called @samp{foo} in the symbol table. This entry
holds the address of an @samp{int} sized block of memory where the
number 1000 is initially stored.
int * a = & foo;
@end smallexample
-looks up the symbol @samp{foo} in the symbol table, gets it address
+looks up the symbol @samp{foo} in the symbol table, gets its address
and then copies this address into the block of memory associated with
the variable @samp{a}.
@group
@var{section} [@var{address}] [(@var{type})] :
[AT(@var{lma})]
- [ALIGN(@var{section_align})]
+ [ALIGN(@var{section_align}) | ALIGN_WITH_INPUT]
[SUBALIGN(@var{subsection_align})]
[@var{constraint}]
@{
@var{output-section-command}
@var{output-section-command}
@dots{}
- @} [>@var{region}] [AT>@var{lma_region}] [:@var{phdr} :@var{phdr} @dots{}] [=@var{fillexp}]
+ @} [>@var{region}] [AT>@var{lma_region}] [:@var{phdr} :@var{phdr} @dots{}] [=@var{fillexp}] [,]
@end group
@end smallexample
The whitespace around @var{section} is required, so that the section
name is unambiguous. The colon and the curly braces are also required.
+The comma at the end may be required if a @var{fillexp} is used and
+the next @var{sections-command} looks like a continuation of the expression.
The line breaks and other white space are optional.
Each @var{output-section-command} may be one of the following:
data.o(.data)
@end smallexample
+To refine the sections that are included based on the section flags
+of an input section, INPUT_SECTION_FLAGS may be used.
+
+Here is a simple example for using Section header flags for ELF sections:
+
+@smallexample
+@group
+SECTIONS @{
+ .text : @{ INPUT_SECTION_FLAGS (SHF_MERGE & SHF_STRINGS) *(.text) @}
+ .text2 : @{ INPUT_SECTION_FLAGS (!SHF_WRITE) *(.text) @}
+@}
+@end group
+@end smallexample
+
+In this example, the output section @samp{.text} will be comprised of any
+input section matching the name *(.text) whose section header flags
+@code{SHF_MERGE} and @code{SHF_STRINGS} are set. The output section
+@samp{.text2} will be comprised of any input section matching the name *(.text)
+whose section header flag @code{SHF_WRITE} is clear.
+
You can also specify files within archives by writing a pattern
matching the archive, a colon, then the pattern matching the file,
with no whitespace around the colon.
@cindex SORT_BY_ALIGNMENT
@code{SORT_BY_ALIGNMENT} is very similar to @code{SORT_BY_NAME}. The
difference is @code{SORT_BY_ALIGNMENT} will sort sections into
-ascending order by alignment before placing them in the output file.
+descending order by alignment before placing them in the output file.
+Larger alignments are placed before smaller alignments in order to
+reduce the amount of padding necessary.
@cindex SORT_BY_INIT_PRIORITY
@code{SORT_BY_INIT_PRIORITY} is very similar to @code{SORT_BY_NAME}. The
@enumerate
@item
@code{SORT_BY_NAME} (@code{SORT_BY_ALIGNMENT} (wildcard section pattern)).
-It will sort the input sections by name first, then by alignment if 2
+It will sort the input sections by name first, then by alignment if two
sections have the same name.
@item
@code{SORT_BY_ALIGNMENT} (@code{SORT_BY_NAME} (wildcard section pattern)).
-It will sort the input sections by alignment first, then by name if 2
+It will sort the input sections by alignment first, then by name if two
sections have the same alignment.
@item
@code{SORT_BY_NAME} (@code{SORT_BY_NAME} (wildcard section pattern)) is
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.
@cindex discarding sections
@cindex sections, discarding
@cindex removing sections
-The linker will not create output sections with no contents. This is
-for convenience when referring to input sections that may or may not
-be present in any of the input files. For example:
+The linker will not normally create output sections with no contents.
+This is for convenience when referring to input sections that may or
+may not be present in any of the input files. For example:
@smallexample
.foo : @{ *(.foo) @}
@end smallexample
will only create a @samp{.foo} section in the output file if there is a
@samp{.foo} section in at least one input file, and if the input
sections are not all empty. Other link script directives that allocate
-space in an output section will also create the output section.
+space in an output section will also create the output section. So
+too will assignments to dot even if the assignment does not create
+space, except for @samp{. = 0}, @samp{. = . + 0}, @samp{. = sym},
+@samp{. = . + sym} and @samp{. = ALIGN (. != 0, expr, 1)} when
+@samp{sym} is an absolute symbol of value 0 defined in the script.
+This allows you to force output of an empty section with @samp{. = .}.
The linker will ignore address assignments (@pxref{Output Section Address})
on discarded output sections, except when the linker script defines
@kindex ALIGN(@var{section_align})
@cindex forcing output section alignment
@cindex output section alignment
-You can increase an output section's alignment by using ALIGN.
+You can increase an output section's alignment by using ALIGN. As an
+alternative you can enforce that the difference between the VMA and LMA remains
+intact throughout this output section with the ALIGN_WITH_INPUT attribute.
@node Forced Input Alignment
@subsubsection Forced Input Alignment
@dots{}
@} [:@var{phdr}@dots{}] [=@var{fill}]
@dots{}
- @} [>@var{region}] [:@var{phdr}@dots{}] [=@var{fill}]
+ @} [>@var{region}] [:@var{phdr}@dots{}] [=@var{fill}] [,]
@end group
@end smallexample
Everything is optional except @code{OVERLAY} (a keyword), and each
section must have a name (@var{secname1} and @var{secname2} above). The
section definitions within the @code{OVERLAY} construct are identical to
-those within the general @code{SECTIONS} contruct (@pxref{SECTIONS}),
+those within the general @code{SECTIONS} construct (@pxref{SECTIONS}),
except that no addresses and no memory regions may be defined for
sections within an @code{OVERLAY}.
+The comma at the end may be required if a @var{fill} is used and
+the next @var{sections-command} looks like a continuation of the expression.
+
The sections are all defined with the same starting address. The load
addresses of the sections are arranged such that they are consecutive in
memory starting at the load address used for the @code{OVERLAY} as a
and defaults to the start address; the start address is also optional,
and defaults to the current value of the location counter).
-If the @code{NOCROSSREFS} keyword is used, and there any references
-among the sections, the linker will report an error. Since the sections
-all run at the same address, it normally does not make sense for one
-section to refer directly to another. @xref{Miscellaneous Commands,
-NOCROSSREFS}.
+If the @code{NOCROSSREFS} keyword is used, and there are any
+references among the sections, the linker will report an error. Since
+the sections all run at the same address, it normally does not make
+sense for one section to refer directly to another.
+@xref{Miscellaneous Commands, NOCROSSREFS}.
For each section within the @code{OVERLAY}, the linker automatically
provides two symbols. The symbol @code{__load_start_@var{secname}} is
with symbol names, file names, or section names. Each memory region
must have a distinct name within the @code{MEMORY} command. However you can
add later alias names to existing memory regions with the @ref{REGION_ALIAS}
-command.
+command.
@cindex memory region attributes
The @var{attr} string is an optional list of attributes that specify
As in C, the linker considers an integer beginning with @samp{0} to be
octal, and an integer beginning with @samp{0x} or @samp{0X} to be
hexadecimal. Alternatively the linker accepts suffixes of @samp{h} or
-@samp{H} for hexadeciaml, @samp{o} or @samp{O} for octal, @samp{b} or
+@samp{H} for hexadecimal, @samp{o} or @samp{O} for octal, @samp{b} or
@samp{B} for binary and @samp{d} or @samp{D} for decimal. Any integer
value without a prefix or a suffix is considered to be decimal.
So for example:
@smallexample
- .text ALIGN (CONSTANT (MAXPAGESIZE)) : @{ *(.text) @}
+ .text ALIGN (CONSTANT (MAXPAGESIZE)) : @{ *(.text) @}
@end smallexample
will create a text section aligned to the largest page boundary
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{.}
address, such as @code{ADDR}, @code{LOADADDR}, @code{ORIGIN} and
@code{SEGMENT_START}. Other terms are simply numbers, or are builtin
functions that return a non-address value, such as @code{LENGTH}.
-
-When the linker evaluates an expression, the result depends on where
-the expression is located in a linker script. Expressions appearing
-outside an output section definitions are evaluated with all terms
-first being converted to absolute addresses before applying operators,
-and evaluate to an absolute address result. Expressions appearing
-inside an output section definition are evaluated with more complex
-rules, but the aim is to treat terms as relative addresses and produce
-a relative address result. In particular, an assignment of a number
-to a symbol results in a symbol relative to the output section with an
-offset given by the number. So, in the following simple example,
+One complication is that unless you set @code{LD_FEATURE ("SANE_EXPR")}
+(@pxref{Miscellaneous Commands}), numbers and absolute symbols are treated
+differently depending on their location, for compatibility with older
+versions of @code{ld}. Expressions appearing outside an output
+section definition treat all numbers as absolute addresses.
+Expressions appearing inside an output section definition treat
+absolute symbols as numbers. If @code{LD_FEATURE ("SANE_EXPR")} is
+given, then absolute symbols and numbers are simply treated as numbers
+everywhere.
+
+In the following simple example,
@smallexample
@group
@code{__data_start} are set to 0x10 relative to the @code{.data}
section in the second two assignments.
-For expressions appearing inside an output section definition
-involving numbers, relative addresses and absolute addresses, ld
-follows these rules to evaluate terms:
+For expressions involving numbers, relative addresses and absolute
+addresses, ld follows these rules to evaluate terms:
@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:
@item
The result of comparisons, @samp{&&} and @samp{||} is also a number.
@item
-The result of other operations on relative addresses (after above
-conversions) is a relative address in the same section as the operand(s).
+The result of other binary arithmetic and logical operations on two
+relative addresses in the same section or two absolute addresses
+(after above conversions) is also a number.
+@item
+The result of other operations on relative addresses or one
+relative address and a number, is a relative address in the same
+section as the relative operand(s).
@item
The result of other operations on absolute addresses (after above
conversions) is an absolute address.
@item DATA_SEGMENT_RELRO_END(@var{offset}, @var{exp})
@kindex DATA_SEGMENT_RELRO_END(@var{offset}, @var{exp})
This defines the end of the @code{PT_GNU_RELRO} segment when
-@samp{-z relro} option is used. Second argument is returned.
+@samp{-z relro} option is used.
When @samp{-z relro} option is not present, @code{DATA_SEGMENT_RELRO_END}
does nothing, otherwise @code{DATA_SEGMENT_ALIGN} is padded so that
@var{exp} + @var{offset} is aligned to the most commonly used page
boundary for particular target. If present in the linker script,
it must always come in between @code{DATA_SEGMENT_ALIGN} and
-@code{DATA_SEGMENT_END}.
+@code{DATA_SEGMENT_END}. Evaluates to the second argument plus any
+padding needed at the end of the @code{PT_GNU_RELRO} segment due to
+section alignment.
@smallexample
. = DATA_SEGMENT_RELRO_END(24, .);
Return the absolute LMA of the named @var{section}. (@pxref{Output
Section LMA}).
+@item LOG2CEIL(@var{exp})
+@kindex LOG2CEIL(@var{exp})
+Return the binary logarithm of @var{exp} rounded towards infinity.
+@code{LOG2CEIL(0)} returns 0.
+
@kindex MAX
@item MAX(@var{exp1}, @var{exp2})
Returns the maximum of @var{exp1} and @var{exp2}.
@item SEGMENT_START(@var{segment}, @var{default})
@kindex SEGMENT_START(@var{segment}, @var{default})
Return the base address of the named @var{segment}. If an explicit
-value has been given for this segment (with a command-line @samp{-T}
-option) that value will be returned; otherwise the value will be
-@var{default}. At present, the @samp{-T} command-line option can only
-be used to set the base address for the ``text'', ``data'', and
+value has already been given for this segment (with a command-line
+@samp{-T} option) then that value will be returned otherwise the value
+will be @var{default}. At present, the @samp{-T} command-line option
+can only be used to set the base address for the ``text'', ``data'', and
``bss'' sections, but you can use @code{SEGMENT_START} with any segment
name.
@ifset I960
* i960:: @command{ld} and the Intel 960 family
@end ifset
+@ifset M68HC11
+* M68HC11/68HC12:: @code{ld} and the Motorola 68HC11 and 68HC12 families
+@end ifset
@ifset ARM
* ARM:: @command{ld} and the ARM family
@end ifset
@ifset M68K
* M68K:: @command{ld} and the Motorola 68K family
@end ifset
+@ifset MIPS
+* MIPS:: @command{ld} and the MIPS family
+@end ifset
@ifset MMIX
* MMIX:: @command{ld} and MMIX
@end ifset
@ifset MSP430
* MSP430:: @command{ld} and MSP430
@end ifset
-@ifset M68HC11
-* M68HC11/68HC12:: @code{ld} and the Motorola 68HC11 and 68HC12 families
+@ifset NDS32
+* NDS32:: @command{ld} and NDS32
+@end ifset
+@ifset NIOSII
+* Nios II:: @command{ld} and the Altera Nios II
@end ifset
@ifset POWERPC
* PowerPC ELF32:: @command{ld} and PowerPC 32-bit ELF Support
@cindex synthesizing on H8/300
@item synthesizing instructions
-@c FIXME: specifically mov.b, or any mov instructions really?
+@c FIXME: specifically mov.b, or any mov instructions really? -> mov.b only, at least on H8, H8H, H8S
@command{ld} finds all @code{mov.b} instructions which use the
sixteen-bit absolute address form, but refer to the top
page of memory, and changes them to use the eight-bit address form.
@samp{mov.b @code{@@}@var{aa}:8} whenever the address @var{aa} is in the
top page of memory).
+@command{ld} finds all @code{mov} instructions which use the register
+indirect with 32-bit displacement addressing mode, but use a small
+displacement inside 16-bit displacement range, and changes them to use
+the 16-bit displacement form. (That is: the linker turns @samp{mov.b
+@code{@@}@var{d}:32,ERx} into @samp{mov.b @code{@@}@var{d}:16,ERx}
+whenever the displacement @var{d} is in the 16 bit signed integer
+range. Only implemented in ELF-format ld).
+
@item bit manipulation instructions
@command{ld} finds all bit manipulation instructions like @code{band, bclr,
biand, bild, bior, bist, bixor, bld, bnot, bor, bset, bst, btst, bxor}
target subroutine is a leaf routine (that is, the target subroutine does
not itself call any subroutines).
-@cindex Cortex-A8 erratum workaround
-@kindex --fix-cortex-a8
-@kindex --no-fix-cortex-a8
-The @samp{--fix-cortex-a8} switch enables a link-time workaround for an erratum in certain Cortex-A8 processors. The workaround is enabled by default if you are targeting the ARM v7-A architecture profile. It can be enabled otherwise by specifying @samp{--fix-cortex-a8}, or disabled unconditionally by specifying @samp{--no-fix-cortex-a8}.
-
-The erratum only affects Thumb-2 code. Please contact ARM for further details.
-
-@kindex --merge-exidx-entries
-@kindex --no-merge-exidx-entries
-The @samp{--no-merge-exidx-entries} switch disables the merging of adjacent exidx entries in debuginfo.
-
@ifclear GENERIC
@lowersections
@end ifclear
@kindex --use-nul-prefixed-import-tables
The @samp{--use-nul-prefixed-import-tables} switch is specifying, that
the import tables idata4 and idata5 have to be generated with a zero
-elememt prefix for import libraries. This is the old style to generate
+element prefix for import libraries. This is the old style to generate
import tables. By default this option is turned off.
@cindex BE8
This allows generation of libraries/applications that work on ARMv4 cores
and are still interworking safe. Note that the above veneer clobbers the
-condition flags, so may cause incorrect progrm behavior in rare cases.
+condition flags, so may cause incorrect program behavior in rare cases.
@cindex USE_BLX
@kindex --use-blx
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 targeting 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 documentation 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
placement of these sequences of instructions - called stubs - is
controlled by the command line option @option{--stub-group-size=N}.
The placement is important because a poor choice can create a need for
-duplicate stubs, increasing the code sizw. The linker will try to
+duplicate stubs, increasing the code size. The linker will try to
group stubs together in order to reduce interruptions to the flow of
code, but it needs guidance as to how big these groups should be and
where they should be placed.
only, because it relies on object files properties not present
otherwise.
+@cindex Cortex-A8 erratum workaround
+@kindex --fix-cortex-a8
+@kindex --no-fix-cortex-a8
+The @samp{--fix-cortex-a8} switch enables a link-time workaround for an erratum in certain Cortex-A8 processors. The workaround is enabled by default if you are targeting the ARM v7-A architecture profile. It can be enabled otherwise by specifying @samp{--fix-cortex-a8}, or disabled unconditionally by specifying @samp{--no-fix-cortex-a8}.
+
+The erratum only affects Thumb-2 code. Please contact ARM for further details.
+
+@cindex Cortex-A53 erratum 835769 workaround
+@kindex --fix-cortex-a53-835769
+@kindex --no-fix-cortex-a53-835769
+The @samp{--fix-cortex-a53-835769} switch enables a link-time workaround for erratum 835769 present on certain early revisions of Cortex-A53 processors. The workaround is disabled by default. It can be enabled by specifying @samp{--fix-cortex-a53-835769}, or disabled unconditionally by specifying @samp{--no-fix-cortex-a53-835769}.
+
+Please contact ARM for further details.
+
+@kindex --merge-exidx-entries
+@kindex --no-merge-exidx-entries
+@cindex Merging exidx entries
+The @samp{--no-merge-exidx-entries} switch disables the merging of adjacent exidx entries in debuginfo.
+
+@kindex --long-plt
+@cindex 32-bit PLT entries
+The @samp{--long-plt} option enables the use of 16 byte PLT entries
+which support up to 4Gb of code. The default is to use 12 byte PLT
+entries which only support 512Mb of code.
+
@ifclear GENERIC
@lowersections
@end ifclear
@end ifclear
@end ifset
+@ifset MIPS
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node MIPS
+@section @command{ld} and the MIPS family
+
+@cindex MIPS microMIPS instruction choice selection
+@kindex --insn32
+@kindex --no-insn32
+The @samp{--insn32} and @samp{--no-insn32} options control the choice of
+microMIPS instructions used in code generated by the linker, such as that
+in the PLT or lazy binding stubs, or in relaxation. If @samp{--insn32} is
+used, then the linker only uses 32-bit instruction encodings. By default
+or if @samp{--no-insn32} is used, all instruction encodings are used,
+including 16-bit ones where possible.
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
@ifset MMIX
@ifclear GENERIC
@raisesections
@end ifclear
@end ifset
+@ifset NDS32
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node NDS32
+@section @code{ld} and NDS32
+@kindex relaxing on NDS32
+For NDS32, there are some options to select relaxation behavior. The linker
+relaxes objects according to these options.
+
+@table @code
+@item @samp{--m[no-]fp-as-gp}
+Disable/enable fp-as-gp relaxation.
+
+@item @samp{--mexport-symbols=FILE}
+Exporting symbols and their address into FILE as linker script.
+
+@item @samp{--m[no-]ex9}
+Disable/enable link-time EX9 relaxation.
+
+@item @samp{--mexport-ex9=FILE}
+Export the EX9 table after linking.
+
+@item @samp{--mimport-ex9=FILE}
+Import the Ex9 table for EX9 relaxation.
+
+@item @samp{--mupdate-ex9}
+Update the existing EX9 table.
+
+@item @samp{--mex9-limit=NUM}
+Maximum number of entries in the ex9 table.
+
+@item @samp{--mex9-loop-aware}
+Avoid generating the EX9 instruction inside the loop.
+
+@item @samp{--m[no-]ifc}
+Disable/enable the link-time IFC optimization.
+
+@item @samp{--mifc-loop-aware}
+Avoid generating the IFC instruction inside the loop.
+@end table
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
+@ifset NIOSII
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node Nios II
+@section @command{ld} and the Altera Nios II
+@cindex Nios II call relaxation
+@kindex --relax on Nios II
+
+Call and immediate jump instructions on Nios II processors are limited to
+transferring control to addresses in the same 256MB memory segment,
+which may result in @command{ld} giving
+@samp{relocation truncated to fit} errors with very large programs.
+The command-line option @option{--relax} enables the generation of
+trampolines that can access the entire 32-bit address space for calls
+outside the normal @code{call} and @code{jmpi} address range. These
+trampolines are inserted at section boundaries, so may not themselves
+be reachable if an input section and its associated call trampolines are
+larger than 256MB.
+
+The @option{--relax} option is enabled by default unless @option{-r}
+is also specified. You can disable trampoline generation by using the
+@option{--no-relax} linker option. You can also disable this optimization
+locally by using the @samp{set .noat} directive in assembly-language
+source files, as the linker-inserted trampolines use the @code{at}
+register as a temporary.
+
+Note that the linker @option{--relax} option is independent of assembler
+relaxation options, and that using the GNU assembler's @option{-relax-all}
+option interferes with the linker's more selective call instruction relaxation.
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
@ifset POWERPC
@ifclear GENERIC
@raisesections
@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
+padded so that they don't cross a 32-byte boundary, or to the
+specified power of two boundary when using @code{--plt-align=}. Note
+that this isn't alignment in the usual sense. 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
symbols known to belong to the system's runtime and libraries. As it will
often not be desirable to export all of a DLL's symbols, which may include
private functions that are not part of any public interface, the command-line
-options listed above may be used to filter symbols out from the list for
+options listed above may be used to filter symbols out from the list for
exporting. The @samp{--output-def} option can be used in order to see the
final list of exported symbols with all exclusions taken into effect.
tools will be able to process object files employing this GNU extension,
but will fail to respect the alignment instructions, and may issue noisy
warnings about unknown linker directives.
+
@end table
@ifclear GENERIC
@printindex cp
@tex
-% I think something like @colophon should be in texinfo. In the
+% I think something like @@colophon should be in texinfo. In the
% meantime:
\long\def\colophon{\hbox to0pt{}\vfill
\centerline{The body of this manual is set in}
\centerline{{\sl\fontname\tensl\/}}
\centerline{are used for emphasis.}\vfill}
\page\colophon
-% Blame: doc@cygnus.com, 28mar91.
+% Blame: doc@@cygnus.com, 28mar91.
@end tex
@bye
projects / platform / upstream / binutils.git / blobdiff