\input texinfo
@setfilename ld.info
-@c Copyright (C) 1991-2014 Free Software Foundation, Inc.
+@c Copyright (C) 1991-2015 Free Software Foundation, Inc.
@syncodeindex ky cp
@c man begin INCLUDE
@include configdoc.texi
@end ifset
version @value{VERSION}.
-Copyright @copyright{} 1991-2014 Free Software Foundation, Inc.
+Copyright @copyright{} 1991-2015 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{} 1991-2014 Free Software Foundation, Inc.
+Copyright @copyright{} 1991-2015 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
different option arguments to enter additional undefined symbols. This
option is equivalent to the @code{EXTERN} linker script command.
+If this option is being used to force additional modules to be pulled
+into the link, and if it is an error for the symbol to remain
+undefined, then the option @option{--require-defined} should be used
+instead.
+
+@kindex --require-defined=@var{symbol}
+@cindex symbols, require defined
+@cindex defined symbol
+@item --require-defined=@var{symbol}
+Require that @var{symbol} is defined in the output file. This option
+is the same as option @option{--undefined} except that if @var{symbol}
+is not defined in the output file then the linker will issue an error
+and exit. The same effect can be achieved in a linker script by using
+@code{EXTERN}, @code{ASSERT} and @code{DEFINED} together. This option
+can be used multiple times to require additional symbols.
+
@kindex -Ur
@cindex constructors
@item -Ur
Disables multiple reloc sections combining.
@item nocopyreloc
-Disables production of copy relocs.
+Disable linker generated .dynbss variables used in place of variables
+defined in shared libraries. May result in dynamic text relocations.
@item nodefaultlib
Marks the object that the search for dependencies of this object will
@item noexecstack
Marks the object as not requiring executable stack.
+@item text
+Treat DT_TEXTREL in shared object as error.
+
+@item notext
+Don't treat DT_TEXTREL in shared object as error.
+
+@item textoff
+Don't treat DT_TEXTREL in shared object as error.
+
@item norelro
Don't create an ELF @code{PT_GNU_RELRO} segment header in the object.
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.
+
+@item noextern-protected-data
+Don't treat protected data symbol as external when building shared
+library. This option overrides linker backend default. It can be used
+to workaround incorrect relocations against protected data symbols
+generated by compiler. Updates on protected data symbols by another
+module aren't visibile to the resulting shared library. Supported for
+i386 and x86-64.
+
@end table
Other keywords are ignored for Solaris compatibility.
context: you may give a hexadecimal constant or the name of an existing
symbol, or use @code{+} and @code{-} to add or subtract hexadecimal
constants or symbols. If you need more elaborate expressions, consider
-using the linker command language from a script (@pxref{Assignments,,
-Assignment: Symbol Definitions}). @emph{Note:} there should be no white
-space between @var{symbol}, the equals sign (``@key{=}''), and
-@var{expression}.
+using the linker command language from a script (@pxref{Assignments}).
+@emph{Note:} there should be no white space between @var{symbol}, the
+equals sign (``@key{=}''), and @var{expression}.
@cindex demangling, from command line
@kindex --demangle[=@var{style}]
Enable garbage collection of unused input sections. It is ignored on
targets that do not support this option. The default behaviour (of not
performing this garbage collection) can be restored by specifying
-@samp{--no-gc-sections} on the command line.
+@samp{--no-gc-sections} on the command line. Note that garbage
+collection for COFF and PE format targets is supported, but the
+implementation is currently considered to be experimental.
@samp{--gc-sections} decides which input sections are used by
examining symbols and relocations. The section containing the entry
other command-line options). This is the string that would appear
in an @code{OUTPUT_FORMAT} linker script command (@pxref{File Commands}).
+@kindex --print-memory-usage
+@cindex memory usage
+@item --print-memory-usage
+Print used size, total size and used size of memory regions created with
+the @ref{MEMORY} command. This is useful on embedded targets to have a
+quick view of amount of free memory. The format of the output has one
+headline and one line per region. It is both human readable and easily
+parsable by tools. Here is an example of an output:
+
+@smallexample
+Memory region Used Size Region Size %age Used
+ ROM: 256 KB 1 MB 25.00%
+ RAM: 32 B 2 GB 0.00%
+@end smallexample
+
@cindex help
@cindex usage
@kindex --help
Only warn once for each undefined symbol, rather than once per module
which refers to it.
+@kindex --warn-orphan
+@kindex --no-warn-orphan
+@cindex warnings, on orphan sections
+@cindex orphan sections, warnings on
+@item --warn-orphan
+The @option{--warn-orphan} option tells the linker to generate a
+warning message whenever it has to place an orphan section into the
+output file. @xref{Orphan Sections}. The @option{--no-warn-orphan}
+option restores the default behaviour of just silently placing these
+sections.
+
@kindex --warn-section-align
@cindex warnings, on section alignment
@cindex section alignment, warnings on
the classic ELF @code{.hash} and new style GNU @code{.gnu.hash}
hash tables. The default is @code{sysv}.
+@kindex --compress-debug-sections=none
+@kindex --compress-debug-sections=zlib
+@kindex --compress-debug-sections=zlib-gnu
+@kindex --compress-debug-sections=zlib-gabi
+@item --compress-debug-sections=none
+@itemx --compress-debug-sections=zlib
+@itemx --compress-debug-sections=zlib-gnu
+@itemx --compress-debug-sections=zlib-gabi
+On ELF platforms , these options control how DWARF debug sections are
+compressed using zlib. @option{--compress-debug-sections=none} doesn't
+compress DWARF debug sections.
+@option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
+sections and rename debug section names to begin with @samp{.zdebug}
+instead of @samp{.debug}. @option{--compress-debug-sections=zlib}
+and @option{--compress-debug-sections=zlib-gabi}
+compress DWARF debug sections with SHF_COMPRESSED from the ELF ABI.
+
@kindex --reduce-memory-overheads
@item --reduce-memory-overheads
This option reduces memory requirements at ld runtime, at the expense of
Ensure that @var{exp} is non-zero. If it is zero, then exit the linker
with an error code, and print @var{message}.
+Note that assertions are checked before the final stages of linking
+take place. This means that expressions involving symbols PROVIDEd
+inside section definitions will fail if the user has not set values
+for those symbols. The only exception to this rule is PROVIDEd
+symbols that just reference dot. Thus an assertion like this:
+
+@smallexample
+ .stack :
+ @{
+ PROVIDE (__stack = .);
+ PROVIDE (__stack_size = 0x100);
+ ASSERT ((__stack > (_end + __stack_size)), "Error: No room left for the stack");
+ @}
+@end smallexample
+
+will fail if @code{__stack_size} is not defined elsewhere. Symbols
+PROVIDEd outside of section definitions are evaluated earlier, so they
+can be used inside ASSERTions. Thus:
+
+@smallexample
+ PROVIDE (__stack_size = 0x100);
+ .stack :
+ @{
+ PROVIDE (__stack = .);
+ ASSERT ((__stack > (_end + __stack_size)), "Error: No room left for the stack");
+ @}
+@end smallexample
+
+will work.
+
@item EXTERN(@var{symbol} @var{symbol} @dots{})
@kindex EXTERN
@cindex undefined symbol in linker script
regions that become too full. The linker will not shuffle sections
around to fit into the available regions.
-A linker script may contain at most one use of the @code{MEMORY}
-command. However, you can define as many blocks of memory within it as
-you wish. The syntax is:
+A linker script may contain many uses of the @code{MEMORY} command,
+however, all memory blocks defined are treated as if they were
+specified inside a single @code{MEMORY} command. The syntax for
+@code{MEMORY} is:
@smallexample
@group
MEMORY
doesn't change the value of the location counter---it just does
arithmetic on it. The two operand @code{ALIGN} allows an arbitrary
expression to be aligned upwards (@code{ALIGN(@var{align})} is
-equivalent to @code{ALIGN(., @var{align})}).
+equivalent to @code{ALIGN(ABSOLUTE(.), @var{align})}).
Here is an example which aligns the output @code{.data} section to the
next @code{0x2000} byte boundary after the preceding section and sets a
@cindex BE8
@kindex --be8
The @samp{--be8} switch instructs @command{ld} to generate BE8 format
-executables. This option is only valid when linking big-endian objects.
-The resulting image will contain big-endian data and little-endian code.
+executables. This option is only valid when linking big-endian
+objects - ie ones which have been assembled with the @option{-EB}
+option. The resulting image will contain big-endian data and
+little-endian code.
@cindex TARGET1
@kindex --target1-rel
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
@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.
+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
projects / binutils-gdb.git / blobdiff