GCC Linker Script教程：详解STM32 CubeIDE链接器语法

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本资源是一份详细的GCC Link脚本手册，主要针对GNU Linker，特别是与STM32平台相关的应用。手册由多个作者共同编撰，包括Steve Chamberlain、Ian Lance Taylor、Red Hat Inc.的代表等，版权属于Free Software Foundation。该手册的版本为2.30.0，适用于GNU Tools for STM32 7-2018-q2-update，更新日期为2019年3月28日。 GCC Linker是GNU Compiler Collection (GCC)的一部分，负责在编译过程之后将程序的不同组件（如代码段、数据段、符号表等）链接成可执行文件或共享库。对于STM32 CubeIDE用户来说，这份手册提供了对Link脚本语法和编码的深入理解，这对于优化程序性能、管理内存布局以及定制目标设备特定的行为至关重要。手册的第一部分是概述，介绍了Linker的基本功能和在软件开发中的作用。它可能涵盖了如何正确配置Linker以适应STM32架构的特性，比如支持32位i386/PET targets、C6X uC Linux targets、Motorola 68HC11/68HC12以及68K等不同处理器系列。接下来的章节详细讲解了Linker Script的使用，这是连接过程中不可或缺的一部分。这部分内容会介绍基本的Linker Script概念，如段定义（如代码段、数据段的创建和分配）、全局和局部符号的处理、重定位和地址计算、以及如何利用Linker Script来控制链接行为和优化空间效率。此外，手册还专门针对特定目标平台的选项进行了分类，如-i386选项针对不同的指令集优化，而针对C6X和Motorola系列的选项则反映了针对这些处理器特有的特性和限制。环境变量的使用也在此部分得到解释，它们在Linker运行时可以用来调整链接过程中的参数。这份GCC Link脚本手册为STM32开发人员提供了一套完整的工具，帮助他们编写高效、优化的链接脚本，确保程序在实际硬件上的正确执行。无论你是初学者还是经验丰富的开发者，理解和掌握这些内容都将极大地提升你的项目质量和开发效率。

Chapter 2: Invocation 9

-L searchdir

--library-path=searchdir

Add path searchdir to the list of paths that ld will search for archive libraries

and ld control scripts. You may use this option any number of times. The

directories are searched in the order in which they are speciﬁed on the command

line. Directories speciﬁed on the command line are searched before the default

directories. All ‘-L’ options apply to all ‘-l’ options, regardless of the order

in which the options appear. ‘-L’ options do not aﬀect how ld searches for a

linker script unless ‘-T’ option is speciﬁed.

If searchdir begins with = or $SYSROOT, then this preﬁx will be replaced by

the sysroot preﬁx, controlled by the ‘--sysroot’ option, or speciﬁed when the

linker is conﬁgured.

The default set of paths searched (without being speciﬁed with ‘-L’) depends

on which emulation mode ld is using, and in some cases also on how it was

conﬁgured. See Section 2.2 [Environment], page 42.

The paths can also be speciﬁed in a link script with the SEARCH_DIR command.

Directories speciﬁed this way are searched at the point in which the linker script

appears in the command line.

-m emulation

Emulate the emulation linker. You can list the available emulations with the

‘--verbose’ or ‘-V’ options.

If the ‘-m’ option is not used, the emulation is taken from the LDEMULATION

environment variable, if that is deﬁned.

Otherwise, the default emulation depends upon how the linker was conﬁgured.

-M

--print-map

Print a link map to the standard output. A link map provides information

about the link, including the following:

• Where object ﬁles are mapped into memory.

• How common symbols are allocated.

• All archive members included in the link, with a mention of the symbol

which caused the archive member to be brought in.

• The values assigned to symbols.

Note - symbols whose values are computed by an expression which involves

a reference to a previous value of the same symbol may not have correct

result displayed in the link map. This is because the linker discards inter-

mediate results and only retains the ﬁnal value of an expression. Under

such circumstances the linker will display the ﬁnal value enclosed by square

brackets. Thus for example a linker script containing:

foo = 1

foo = foo * 4

foo = foo + 8

will produce the following output in the link map if the ‘-M’ option is used:

0x00000001 foo = 0x1

10 The GNU linker

[0x0000000c] foo = (foo * 0x4)

[0x0000000c] foo = (foo + 0x8)

See Section 3.10 [Expressions], page 77 for more information about expres-

sions in linker scripts.

-n

--nmagic Turn oﬀ page alignment of sections, and disable linking against shared libraries.

If the output format supports Unix style magic numbers, mark the output as

NMAGIC.

-N

--omagic Set the text and data sections to be readable and writable. Also, do not page-

align the data segment, and disable linking against shared libraries. If the

output format supports Unix style magic numbers, mark the output as OMAGIC.

Note: Although a writable text section is allowed for PE-COFF targets, it does

not conform to the format speciﬁcation published by Microsoft.

--no-omagic

This option negates most of the eﬀects of the ‘-N’ option. It sets the text section

to be read-only, and forces the data segment to be page-aligned. Note - this

option does not enable linking against shared libraries. Use ‘-Bdynamic’ for

this.

-o output

--output=output

Use output as the name for the program produced by ld; if this option is not

speciﬁed, the name ‘a.out’ is used by default. The script command OUTPUT

can also specify the output ﬁle name.

-O level If level is a numeric values greater than zero ld optimizes the output. This

might take signiﬁcantly longer and therefore probably should only be enabled

for the ﬁnal binary. At the moment this option only aﬀects ELF shared library

generation. Future releases of the linker may make more use of this option. Also

currently there is no diﬀerence in the linker’s behaviour for diﬀerent non-zero

values of this option. Again this may change with future releases.

-plugin name

Involve a plugin in the linking process. The name parameter is the absolute

ﬁlename of the plugin. Usually this parameter is automatically added by the

complier, when using link time optimization, but users can also add their own

plugins if they so wish.

Note that the location of the compiler originated plugins is diﬀerent from the

place where the ar, nm and ranlib programs search for their plugins. In or-

der for those commands to make use of a compiler based plugin it must ﬁrst

be copied into the ‘${libdir}/bfd-plugins’ directory. All gcc based linker

plugins are backward compatible, so it is suﬃcient to just copy in the newest

one.

Chapter 2: Invocation 11

--push-state

The ‘--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 corre-

sponding ‘--pop-state’ option.

The option which are covered are: ‘-Bdynamic’, ‘-Bstatic’, ‘-dn’, ‘-dy’,

‘-call_shared’, ‘-non_shared’, ‘-static’, ‘-N’, ‘-n’, ‘--whole-archive’,

‘--no-whole-archive’, ‘-r’, ‘-Ur’, ‘--copy-dt-needed-entries’,

‘--no-copy-dt-needed-entries’, ‘--as-needed’, ‘--no-as-needed’, and

‘-a’.

One target for this option are speciﬁcations for ‘pkg-config’. When used with

the ‘--libs’ option all possibly needed libraries are listed and then possibly

linked with all the time. It is better to return something as follows:

-Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state

--pop-state

Undoes the eﬀect of –push-state, restores the previous values of the ﬂags gov-

erning input ﬁle handling.

-q

--emit-relocs

Leave relocation sections and contents in fully linked executables. Post link

analysis and optimization tools may need this information in order to perform

correct modiﬁcations of executables. This results in larger executables.

This option is currently only supported on ELF platforms.

--force-dynamic

Force the output ﬁle to have dynamic sections. This option is speciﬁc to Vx-

Works targets.

-r

--relocatable

Generate relocatable output—i.e., generate an output ﬁle that can in turn serve

as input to ld. This is often called partial linking. As a side eﬀect, in envi-

ronments that support standard Unix magic numbers, this option also sets the

output ﬁle’s magic number to OMAGIC. If this option is not speciﬁed, an abso-

lute ﬁle is produced. When linking C++ programs, this option will not resolve

references to constructors; to do that, use ‘-Ur’.

When an input ﬁle does not have the same format as the output ﬁle, partial

linking is only supported if that input ﬁle does not contain any relocations.

Diﬀerent output formats can have further restrictions; for example some a.out-

based formats do not support partial linking with input ﬁles in other formats

at all.

This option does the same thing as ‘-i’.

-R filename

--just-symbols=filename

Read symbol names and their addresses from ﬁlename, but do not relocate it

or include it in the output. This allows your output ﬁle to refer symbolically

12 The GNU linker

to absolute locations of memory deﬁned in other programs. You may use this

option more than once.

For compatibility with other ELF linkers, if the ‘-R’ option is followed by a

directory name, rather than a ﬁle name, it is treated as the ‘-rpath’ option.

-s

--strip-all

Omit all symbol information from the output ﬁle.

-S

--strip-debug

Omit debugger symbol information (but not all symbols) from the output ﬁle.

--strip-discarded

--no-strip-discarded

Omit (or do not omit) global symbols deﬁned in discarded sections. Enabled

by default.

-t

--trace Print the names of the input ﬁles as ld processes them.

-T scriptfile

--script=scriptfile

Use scriptﬁle as the linker script. This script replaces ld’s default linker script

(rather than adding to it), so commandﬁle must specify everything necessary

to describe the output ﬁle. See Chapter 3 [Scripts], page 45. If scriptﬁle does

not exist in the current directory, ld looks for it in the directories speciﬁed by

any preceding ‘-L’ options. Multiple ‘-T’ options accumulate.

-dT scriptfile

--default-script=scriptfile

Use scriptﬁle as the default linker script. See Chapter 3 [Scripts], page 45.

This option is similar to the ‘--script’ option except that processing of the

script is delayed until after the rest of the command line has been processed.

This allows options placed after the ‘--default-script’ option on the com-

mand line to aﬀect the behaviour of the linker script, which can be important

when the linker command line cannot be directly controlled by the user. (eg

because the command line is being constructed by another tool, such as ‘gcc’).

-u symbol

--undefined=symbol

Force symbol to be entered in the output ﬁle as an undeﬁned symbol. Do-

ing this may, for example, trigger linking of additional modules from standard

libraries. ‘-u’ may be repeated with diﬀerent option arguments to enter addi-

tional undeﬁned symbols. This option is equivalent to the 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

‘--require-defined’ should be used instead.

Chapter 2: Invocation 13

--require-defined=symbol

Require that symbol is deﬁned in the output ﬁle. This option is the same as

option ‘--undefined’ except that if 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 EXTERN, ASSERT and DEFINED together. This option

can be used multiple times to require additional symbols.

-Ur For anything other than C++ programs, this option is equivalent to ‘-r’: it gen-

erates relocatable output—i.e., an output ﬁle that can in turn serve as input to

ld. When linking C++ programs, ‘-Ur’ does resolve references to constructors,

unlike ‘-r’. It does not work to use ‘-Ur’ on ﬁles that were themselves linked

with ‘-Ur’; once the constructor table has been built, it cannot be added to.

Use ‘-Ur’ only for the last partial link, and ‘-r’ for the others.

--orphan-handling=MODE

Control how orphan sections are handled. An orphan section is one not speciﬁ-

cally mentioned in a linker script. See Section 3.10.4 [Orphan Sections], page 78.

MODE can have any of the following values:

place Orphan sections are placed into a suitable output section following

the strategy described in Section 3.10.4 [Orphan Sections], page 78.

The option ‘--unique’ also aﬀects how sections are placed.

discard All orphan sections are discarded, by placing them in the

‘/DISCARD/’ section (see Section 3.6.7 [Output Section Discarding],

page 66).

warn The linker will place the orphan section as for place and also issue

a warning.

error The linker will exit with an error if any orphan section is found.

The default if ‘--orphan-handling’ is not given is place.

--unique[=SECTION ]

Creates a separate output section for every input section matching SECTION,

or if the optional wildcard SECTION argument is missing, for every orphan

input section. An orphan section is one not speciﬁcally mentioned in a linker

script. You may use this option multiple times on the command line; It prevents

the normal merging of input sections with the same name, overriding output

section assignments in a linker script.

-v

--version

-V Display the version number for ld. The ‘-V’ option also lists the supported

emulations.

-x

--discard-all

Delete all local symbols.

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