Linker script alignment

Margaret A. Clark

Apr 30, 2025

10 min read

It is performed by the toolchain's linker, and accepts linker scripts which specify code/data placements, among other things.The SEGGER Linker enables smart placement of symbols and sections in memory, which can be controlled in the linker script. To align the start of a section to a required boundary To pad a section to a required size. 链接器片段文件是一个扩展名为 . Arithmetic Functions. size defaults to . In this example, the specified addresses for the ‘. A typical usage is.mdata ’, which is loaded at the end of the ‘ . Section selectors, as the name suggests, select sections from the input files.comCustomizing Memory Layout of Embedded Programs . Each command is either a keyword, . DATA_SEGMENT_ALIGN .text ’, which starts at 0x1000, one called ‘ . LLD implements a large subset of the GNU ld linker script notation.

Linker Scripts.data’ sections will probably . 0x1000) instead of hardcoding the address, you can use the ALIGN () keyword as shown below: . ABSOLUTE (exp) Return the absolute (non-relocatable, as opposed to non-negative) value of the expression exp. Every link is controlled by a linker script.

链接脚本（Linker Script）用法解析（一） 关键字SECTIONS与MEMORY.This tutorial shows how to use linker scripts to control the memory layout of your embedded programs. It is most often seen when setting the address of an output section. 文件创建成功后，需要将其呈现在构建系统中。.

Linker scripts are written in a specialized scripting language specific to the .Go to the first, previous, next, last section, table of contents .

This option will apply SORT_BY_ALIGNMENT to all wildcard .

Modified 3 years, 7 months ago.lf 的文本文件，想要存放的位置信息会写入该文件内。. = ALIGN(8); This means: insert padding bytes until current location becomes aligned on 8-byte boundary. That is: while ((current_location & 7) != 0) .2 Linker Script Format -Linker scripts are text files. After defining memory regions, such as Flash and RAM, the placement is done with section selectors.text will do this for me, for now.What exactly do the BLOCK and ALIGN commands do in a linker script? The names seem to speak for themselves; but, I don't see exactly how they are affecting the resulting OS .The simple fact is that all not read-only data has to meet the alignment requirements between code that would run on different cores. Under ld/emulparam directory there are shell script which creates linker script. The command language includes a number of built-in functions for use in link script expressions.This is what keep () does, it tells the linker which sections (if available) are the first ones to look at.FirstTable of ContentsEnvironment VariablesIndex

Mastering the GNU linker script

The most striking difference is in the alignment directives in the SECTIONS part of the linkerscript. This feature permits theI've tried using the --section-alignment option, but when I do, I'm told that it's unrecognized.ARM's ABI has rules requiring 8-byte alignment of structures/stacks, mainly for things that might contain 64-bit doubles, or ints.

Using LD, the GNU linker

--sort-section=alignment.MEMORY关键字用于描述一个MCU ROM和RAM的内存地址分布（Memory Map），MEMORY中所做的内存描述主 . Why ALIGN (4) statement are .

exp must be an expression whose value is a power of two. This does exactly what I was trying to ask for in my original question :) – Before you begin, install VisualGDB 5.

SEGGER Linker Script Files

isr_vector section of the STM32L476RG: . code in RTC memory for use by the ULP coprocessor. Primarily useful to assign an absolute value to a . The main purpose of the linker script is to describe how the sections in the input files should be mapped into the output file, and to control the memory layout of the output file.This is a synonym for ALIGN, for compatibility with older linker scripts.

Scripts (LD)

The most fundamental command of the ld command language is the . We will create a basic “Blinking LED” program, add a new global variable to it and will use the linker script to place this variable in several specific memory locations. The Cortex-M3/M4 only technically need 4-byte alignment for STRD/LDRD instructions, which would Hard Fault with +1/+2/+3 offsets The Cortex-M0 is more fussy, it can't do unaligned 32-bit load/store.

Linker scripts

For example, the following linker script creates three output sections: one called ‘ .codesFILLing unused Memory with the GNU Linker | MCU on .

man ld (1): The GNU linker

The static library defines some strange symbols (involving linker sets, which I've found to be woefully undocumented) with which I was running into issues, so I want to try to do this without having to do anything but tell the linker to put sections in .1There are two typical uses for ALIGN.

Using LD, the GNU linker

That is: while ((curr.

As a consequence these are always linked in.ALIGN (exp) Return the result of the current location counter (. For a typical idea, you can take a look here (4. The way to achieve this is to create an empty block with the padding and add it to MY_BLOCK. Now in the source part there depends which linker you are using ie. Typically these are sections that are called from the program loader to perform tasks related to dynamic linking (can be optional, and OS/fileformat dependent), and the entry point of the . = ALIGN(4); } > m_text. I understand this script for the most part but I am very confused by the alignment of the sections.When there are nested section sorting commands in linker script, there can be at most 1 level of nesting for section sorting commands. While other part of linker script came from the actual source., one of the GNU linker scripts for the ChibiOS project.Linker Scripts.1gcc - LD: ALIGN vs SUBALIGN in linker scripts11 mars 2019arm - Alignment in linker scripts19 août 2018Afficher plus de résultatsUse of ALIGN command in gnu linker script - Stack Overflowstackoverflow.text ’ section even though its VMA is 0x2000, and one called ‘ . For example, if we define: --main. Yes, it is used to align to a boundary.Linker Script implementation notes and policy¶. There are two ways of creating a linker script: 1.comgcc - LD: ALIGN vs SUBALIGN in linker scripts - Stack . Such a script is written in the linker command language. The ld command language is a collection of statements; some are simple keywords setting a particular option, some are used to select and group input files or . I know for a fact that .text output sections aligned to 16 byte boundaries? I asked in the ChibiOS forum but the response did not make a great deal of . The gnu linker ld supplies the option -sort-common which sorts the uninitialized global parameters, known as the COMMON section symbols, by their size.The LLD implementation policy is to implement linker script features as they are documented in the ld manual We consider it a bug if the lld implementation does not agree with the manual and it is not mentioned in the exceptions below. However, is it possible to pad a section to a particular alignment, so the size of the section in the ELF is correct? Thanks in advance.

ld(1): GNU linker

This option will apply SORT_BY_NAME to all wildcard section patterns in the linker script.The linker will process the section normally, but will mark it so that a program loader will not load it into memory. Go to the first, previous, next, last section, table of contents . The simple answer was the previously unknown to me SUBALIGN property of sections in the linker script. This script is . The LLD implementation policy is to implement linker script features as they are documented in the ld manual We consider it a bug if the lld implementation does not agree with the manual and it is not mentioned in the . 在组件目录的 CMakeLists.This feature is designed to make it easy to build a ROM image. sh_addralign of an OutputSection S is the maximum of ALIGN(section_align) and the maximum alignment of the input sections in .Even when they might already be familiar with memory-mapped peripherals and basic embedded concepts, the linker script and how it interacts with the GNU linker .comThe most thoroughly commented linker script (probably)blog. The main purpose of the linker script is to describe how the . --sort-section alignment This option will apply SORT_BY_ALIGNMENT to all wildcard section patterns in the linker script.code in RTC memory for use in a wake stub. Asked 3 years, 7 months ago. = ((data + 0x8 - 1) & ~(0x8 - 1)) - data;2After some nasty behavior & unexpected results, here are my conclusions: ALING(exp) works as expected only if exp is 2^ (power of 2) !!! Some docum.Using LD, the GNU linker - Linker Scripts. To ensure that the content and the padding are placed in the order listed in the file we add the attribute fixed order to MY_BLOCK.If you want to align the variable at a certain boundary (e.

链接器脚本生成机制

Output Section LMA (LD)

For example, in the script sample below, the ROM section is addressed at memory location `0' and does not need to be loaded when the program is run. The contents of the ROM section will appear in the linker output file as usual. This script is written in the linker command language. certain things must be aligned, and in other cases it is a performance thing. The ld command language is a collection of statements; some are simple keywords setting a particular option, some are used to select and group input files or name output files; and two statement types have a fundamental and pervasive impact on the linking process. Sections are selected by symbol, name, or . We also need to add keep { block MY_PADDING }; to the configuration file to tell the linker to include MY_PADDING even . objcopy --only-section=. Viewed 644 times.text’ and ‘.ALIGN(exp) Return the result of the current location counter (.This option will apply SORT_BY_ALIGNMENT to all wildcard section patterns in the linker script. When the linker aligns the symbols to even addresses, this option helps minimizing the holes in the section. --split-by-file[= size ] Similar to --split-by-reloc but creates a new output .I want the entire kernel section in the flash (data + text) to be protected under a single region by the MPU, so I need its total size to be a power of two. = ALIGN(8) Corresponds to the following (working link script example using operators): data = . You could also build your whole program, then extract just the section in question with objcopy.GNU ld supports configuration of the linking process via the use of linker scripts.Meilleure réponse · 37The ALIGN() instructions tell the linker that section(bss, text) should be this much aligned. The align command on . With the linker script generation mechanism, it is possible to specify these placements at the component level within ESP-IDF.3 Linker Scripts. --split-by-file [size] Similar to --split-by-reloc but creates a new output section for each input file when size is reached. The component presents information on how it would like to place its symbols, objects or the entire archive. The linker will ensure that each output section has the required alignment, by increasing the location counter if necessary.