\input texinfo
@setfilename ld.info
-@c Copyright (C) 1991-2018 Free Software Foundation, Inc.
+@c Copyright (C) 1991-2019 Free Software Foundation, Inc.
@syncodeindex ky cp
@c man begin INCLUDE
@include configdoc.texi
@end ifset
version @value{VERSION}.
-Copyright @copyright{} 1991-2018 Free Software Foundation, Inc.
+Copyright @copyright{} 1991-2019 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{} 1991-2018 Free Software Foundation, Inc.
+Copyright @copyright{} 1991-2019 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
in the filter object. The shared object @var{name} need not exist.
Thus the shared object @var{name} may be used to provide an alternative
implementation of certain functions, perhaps for debugging or for
-machine specific performance.
+machine-specific performance.
This option may be specified more than once. The DT_AUXILIARY entries
will be created in the order in which they appear on the command line.
See @ref{Expressions} for more information about expressions in linker
scripts.
+
+@item
+How GNU properties are merged.
+
+When the linker merges input .note.gnu.property sections into one output
+.note.gnu.property section, some properties are removed or updated.
+These actions are reported in the link map. For example:
+
+@smallexample
+Removed property 0xc0000002 to merge foo.o (0x1) and bar.o (not found)
+@end smallexample
+
+This indicates that property 0xc0000002 is removed from output when
+merging properties in @file{foo.o}, whose property 0xc0000002 value
+is 0x1, and @file{bar.o}, which doesn't have property 0xc0000002.
+
+@smallexample
+Updated property 0xc0010001 (0x1) to merge foo.o (0x1) and bar.o (0x1)
+@end smallexample
+
+This indicates that property 0xc0010001 value is updated to 0x1 in output
+when merging properties in @file{foo.o}, whose 0xc0010001 property value
+is 0x1, and @file{bar.o}, whose 0xc0010001 property value is 0x1.
@end itemize
+@cindex link map discarded
+@kindex --print-map-discarded
+@kindex --no-print-map-discarded
+@item --print-map-discarded
+@itemx --no-print-map-discarded
+Print (or do not print) the list of discarded and garbage collected sections
+in the link map. Enabled by default.
+
@kindex -n
@cindex read-only text
@cindex NMAGIC
@cindex input files, displaying
@item -t
@itemx --trace
-Print the names of the input files as @command{ld} processes them.
+Print the names of the input files as @command{ld} processes them. If
+@samp{-t} is given twice then members within archives are also printed.
+@samp{-t} output is useful to generate a list of all the object files
+and scripts involved in linking, for example, when packaging files for
+a linker bug report.
@kindex -T @var{script}
@kindex --script=@var{script}
@option{call-nop=suffix-@var{byte}} generates @code{call foo @var{byte}}.
Supported for i386 and x86_64.
+@item cet-report=none
+@itemx cet-report=warning
+@itemx cet-report=error
+Specify how to report the missing GNU_PROPERTY_X86_FEATURE_1_IBT and
+GNU_PROPERTY_X86_FEATURE_1_SHSTK properties in input .note.gnu.property
+section. @option{cet-report=none}, which is the default, will make the
+linker not report missing properties in input files.
+@option{cet-report=warning} will make the linker issue a warning for
+missing properties in input files. @option{cet-report=error} will make
+the linker issue an error for missing properties in input files.
+Note that @option{ibt} will turn off the missing
+GNU_PROPERTY_X86_FEATURE_1_IBT property report and @option{shstk} will
+turn off the missing GNU_PROPERTY_X86_FEATURE_1_SHSTK property report.
+Supported for Linux/i386 and Linux/x86_64.
+
@item combreloc
@itemx nocombreloc
Combine multiple dynamic relocation sections and sort to improve
archive is needed to resolve an undefined symbol referred to by an
object in an archive that appears later on the command line, the linker
would not be able to resolve that reference. By grouping the archives,
-they all be searched repeatedly until all possible references are
+they will all be searched repeatedly until all possible references are
resolved.
Using this option has a significant performance cost. It is best to use
When creating a shared library, bind references to global symbols to the
definition within the shared library, if any. Normally, it is possible
for a program linked against a shared library to override the definition
-within the shared library. This option can also be used with the
-@option{--export-dynamic} option, when creating a position independent
-executable, to bind references to global symbols to the definition within
-the executable. This option is only meaningful on ELF platforms which
-support shared libraries and position independent executables.
+within the shared library. This option is only meaningful on ELF
+platforms which support shared libraries.
@kindex -Bsymbolic-functions
@item -Bsymbolic-functions
When creating a shared library, bind references to global function
symbols to the definition within the shared library, if any.
-This option can also be used with the @option{--export-dynamic} option,
-when creating a position independent executable, to bind references
-to global function symbols to the definition within the executable.
This option is only meaningful on ELF platforms which support shared
-libraries and position independent executables.
+libraries.
@kindex --dynamic-list=@var{dynamic-list-file}
@item --dynamic-list=@var{dynamic-list-file}
@kindex --embedded-relocs
@item --embedded-relocs
This option is similar to the @option{--emit-relocs} option except
-that the relocs are stored in a target specific section. This option
+that the relocs are stored in a target-specific section. This option
is only supported by the @samp{BFIN}, @samp{CR16} and @emph{M68K}
targets.
@kindex --target-help
@item --target-help
-Print a summary of all target specific options on the standard output and exit.
+Print a summary of all target-specific options on the standard output and exit.
@kindex -Map=@var{mapfile}
@item -Map=@var{mapfile}
@xref{PowerPC ELF32,,@command{ld} and PowerPC 32-bit ELF Support}.
@end ifset
-On some platforms the @samp{--relax} option performs target specific,
+On some platforms the @samp{--relax} option performs target-specific,
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
Add a directory to the runtime library search path. This is used when
linking an ELF executable with shared objects. All @option{-rpath}
arguments are concatenated and passed to the runtime linker, which uses
-them to locate shared objects at runtime. The @option{-rpath} option is
-also used when locating shared objects which are needed by shared
-objects explicitly included in the link; see the description of the
-@option{-rpath-link} option. If @option{-rpath} is not used when linking an
-ELF executable, the contents of the environment variable
-@code{LD_RUN_PATH} will be used if it is defined.
+them to locate shared objects at runtime.
+
+The @option{-rpath} option is also used when locating shared objects which
+are needed by shared objects explicitly included in the link; see the
+description of the @option{-rpath-link} option. Searching @option{-rpath}
+in this way is only supported by native linkers and cross linkers which
+have been configured with the @option{--with-sysroot} option.
+
+If @option{-rpath} is not used when linking an ELF executable, the
+contents of the environment variable @code{LD_RUN_PATH} will be used if it
+is defined.
The @option{-rpath} option may also be used on SunOS. By default, on
SunOS, the linker will form a runtime search path out of all the
file as @code{__wrap_malloc}; if you do, the assembler may resolve the
call before the linker has a chance to wrap it to @code{malloc}.
+Only undefined references are replaced by the linker. So, translation unit
+internal references to @var{symbol} are not resolved to
+@code{__wrap_@var{symbol}}. In the next example, the call to @code{f} in
+@code{g} is not resolved to @code{__wrap_f}.
+
+@smallexample
+int
+f (void)
+@{
+ return 123;
+@}
+
+int
+g (void)
+@{
+ return f();
+@}
+@end smallexample
+
@kindex --eh-frame-hdr
@kindex --no-eh-frame-hdr
@item --eh-frame-hdr
a check is made causing the loss of an ISA mode transition to produce
an error.
+@kindex --compact-branches
+@item --compact-branches
+@kindex --no-compact-branches
+@item --compact-branches
+These options control the generation of compact instructions by the linker
+in the PLT entries for MIPS R6.
+
@end table
@c man end
@item
the @code{ENTRY(@var{symbol})} command in a linker script;
@item
-the value of a target specific symbol, if it is defined; For many
+the value of a target-specific symbol, if it is defined; For many
targets this is @code{start}, but PE- and BeOS-based systems for example
check a list of possible entry symbols, matching the first one found.
@item
into ascending order by name before placing them in the output file.
@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
-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.
+@code{SORT_BY_ALIGNMENT} is similar to @code{SORT_BY_NAME}.
+@code{SORT_BY_ALIGNMENT} will sort sections into descending order of
+alignment before placing them in the output file. Placing larger
+alignments before smaller alignments can reduce the amount of padding
+needed.
@cindex SORT_BY_INIT_PRIORITY
-@code{SORT_BY_INIT_PRIORITY} is very similar to @code{SORT_BY_NAME}. The
-difference is @code{SORT_BY_INIT_PRIORITY} will sort sections into
-ascending order by numerical value of the GCC init_priority attribute
-encoded in the section name before placing them in the output file.
+@code{SORT_BY_INIT_PRIORITY} is also similar to @code{SORT_BY_NAME}.
+@code{SORT_BY_INIT_PRIORITY} will sort sections into ascending
+numerical order of the GCC init_priority attribute encoded in the
+section name before placing them in the output file. In
+@code{.init_array.NNNNN} and @code{.fini_array.NNNNN}, @code{NNNNN} is
+the init_priority. In @code{.ctors.NNNNN} and @code{.dtors.NNNNN},
+@code{NNNNN} is 65535 minus the init_priority.
@cindex SORT
@code{SORT} is an alias for @code{SORT_BY_NAME}.
input sections. Any input sections which are assigned to an output
section named @samp{/DISCARD/} are not included in the output file.
+Note, sections that match the @samp{/DISCARD/} output section will be
+discarded even if they are in an ELF section group which has other
+members which are not being discarded. This is deliberate.
+Discarding takes precedence over grouping.
+
@node Output Section Attributes
@subsection Output Section Attributes
@cindex output section attributes
@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}]
@{
Invert the sense of any of the attributes that follow
@end table
-If a unmapped section matches any of the listed attributes other than
+If an unmapped section matches any of the listed attributes other than
@samp{!}, it will be placed in the memory region. The @samp{!}
-attribute reverses this test, so that an unmapped section will be placed
-in the memory region only if it does not match any of the listed
-attributes.
+attribute reverses the test for the characters that follow, so that an
+unmapped section will be placed in the memory region only if it does
+not match any of the attributes listed afterwards. Thus an attribute
+string of @samp{RW!X} will match any unmapped section that has either
+or both of the @samp{R} and @samp{W} attributes, but only as long as
+the section does not also have the @samp{X} attribute.
@kindex ORIGIN =
@kindex o =
@subsection Symbolic Constants
@cindex symbolic constants
@kindex CONSTANT
-It is possible to refer to target specific constants via the use of
+It is possible to refer to target-specific constants via the use of
the @code{CONSTANT(@var{name})} operator, where @var{name} is one of:
@table @code
projects / deliverable / binutils-gdb.git / blobdiff