ALIGN(n) различия в разделах линкерскрипта в семействе STM32
Я сравниваю скрипты линкеров, сгенерированные CubeMX для семейства микроконтроллеров STM32. Давайте посмотрим на STM32L476RG (NUCLEO-L476) и более свежий STM32F767ZI (NUCLEO-F767ZI).
Примечание: линкскрипты создаются для arm-none-eabi-gcc компилятор.
Самым поразительным отличием являются директивы выравнивания в SECTIONS часть линкерскрипта. Здесь .isr_vector раздел STM32L476RG:
.isr_vector :
{
. = ALIGN(8);
KEEP(*(.isr_vector)) /* Startup code */
. = ALIGN(8);
} >FLASH
И это .isr_vector раздел для STM32F767ZI:
.isr_vector :
{
. = ALIGN(4);
KEEP(*(.isr_vector)) /* Startup code */
. = ALIGN(4);
} >FLASH
Подобные различия есть практически во всех разделах кода. Я сделал таблицу для сравнения:
STM32L476RG STM32F767ZI
+----------------+----------+ +----------------+----------+
| .isr_vector | ALIGN(8) | | .isr_vector | ALIGN(4) |
+----------------+----------+ +----------------+----------+
| .text | ALIGN(8) | | .text | ALIGN(4) |
+----------------+----------+ +----------------+----------+
| .rodata | ALIGN(8) | | .rodata | ALIGN(4) |
+----------------+----------+ +----------------+----------+
| .ARM.extab | ALIGN(8) | | .ARM.extab | / |
+----------------+----------+ +----------------+----------+
| .ARM | ALIGN(8) | | .ARM | / |
+----------------+----------+ +----------------+----------+
| .preinit_array | ALIGN(8) | | .preinit_array | / |
+----------------+----------+ +----------------+----------+
| .init_array | ALIGN(8) | | .init_array | / |
+----------------+----------+ +----------------+----------+
| .fini_array | ALIGN(8) | | .fini_array | / |
+----------------+----------+ +----------------+----------+
| .data | ALIGN(8) | | .data | ALIGN(4) |
+----------------+----------+ +----------------+----------+
| .bss | / | | .bss | / |
+----------------+----------+ +----------------+----------+
| ._user_heap_st | ALIGN(8) | | ._user_heap_st | ALIGN(8) |
+----------------+----------+ +----------------+----------+
| .ARM.attributes| / | | .ARM.attributes| / |
+----------------+----------+ +----------------+----------+
Учитывая тот факт, что оба микроконтроллера имеют 32-битную архитектуру, откуда эти различия?
Для полноты я решил добавить полные ссылки на скрипты здесь. Вы можете использовать онлайн-инструмент для сравнения ( https://www.diffchecker.com/). Ниже приведен линкерскрипт для микроконтроллера STM32L476RG:
/*
*****************************************************************************
**
** File : LinkerScript.ld
**
** Abstract : Linker script for STM32L476RGTx Device with
** 1024KByte FLASH, 128KByte RAM
**
** Set heap size, stack size and stack location according
** to application requirements.
**
** Set memory bank area and size if external memory is used.
**
** Target : STMicroelectronics STM32
**
**
** Distribution: The file is distributed as is, without any warranty
** of any kind.
**
*****************************************************************************
** @attention
**
** <h2><center>© COPYRIGHT(c) 2014 Ac6</center></h2>
**
** Redistribution and use in source and binary forms, with or without modification,
** are permitted provided that the following conditions are met:
** 1. Redistributions of source code must retain the above copyright notice,
** this list of conditions and the following disclaimer.
** 2. Redistributions in binary form must reproduce the above copyright notice,
** this list of conditions and the following disclaimer in the documentation
** and/or other materials provided with the distribution.
** 3. Neither the name of Ac6 nor the names of its contributors
** may be used to endorse or promote products derived from this software
** without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
** AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
** DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
** SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
** OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
**
*****************************************************************************
*/
/* Entry Point */
ENTRY(Reset_Handler)
/* Highest address of the user mode stack */
_estack = 0x20018000; /* end of RAM */
/* Generate a link error if heap and stack don't fit into RAM */
_Min_Heap_Size = 0x200; /* required amount of heap */
_Min_Stack_Size = 0x400; /* required amount of stack */
/* Specify the memory areas */
MEMORY
{
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 96K
RAM2 (xrw) : ORIGIN = 0x10000000, LENGTH = 32K
FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 1024K
}
/* Define output sections */
SECTIONS
{
/* The startup code goes first into FLASH */
.isr_vector :
{
. = ALIGN(8);
KEEP(*(.isr_vector)) /* Startup code */
. = ALIGN(8);
} >FLASH
/* The program code and other data goes into FLASH */
.text :
{
. = ALIGN(8);
*(.text) /* .text sections (code) */
*(.text*) /* .text* sections (code) */
*(.glue_7) /* glue arm to thumb code */
*(.glue_7t) /* glue thumb to arm code */
*(.eh_frame)
KEEP (*(.init))
KEEP (*(.fini))
. = ALIGN(8);
_etext = .; /* define a global symbols at end of code */
} >FLASH
/* Constant data goes into FLASH */
.rodata :
{
. = ALIGN(8);
*(.rodata) /* .rodata sections (constants, strings, etc.) */
*(.rodata*) /* .rodata* sections (constants, strings, etc.) */
. = ALIGN(8);
} >FLASH
.ARM.extab :
{
. = ALIGN(8);
*(.ARM.extab* .gnu.linkonce.armextab.*)
. = ALIGN(8);
} >FLASH
.ARM : {
. = ALIGN(8);
__exidx_start = .;
*(.ARM.exidx*)
__exidx_end = .;
. = ALIGN(8);
} >FLASH
.preinit_array :
{
. = ALIGN(8);
PROVIDE_HIDDEN (__preinit_array_start = .);
KEEP (*(.preinit_array*))
PROVIDE_HIDDEN (__preinit_array_end = .);
. = ALIGN(8);
} >FLASH
.init_array :
{
. = ALIGN(8);
PROVIDE_HIDDEN (__init_array_start = .);
KEEP (*(SORT(.init_array.*)))
KEEP (*(.init_array*))
PROVIDE_HIDDEN (__init_array_end = .);
. = ALIGN(8);
} >FLASH
.fini_array :
{
. = ALIGN(8);
PROVIDE_HIDDEN (__fini_array_start = .);
KEEP (*(SORT(.fini_array.*)))
KEEP (*(.fini_array*))
PROVIDE_HIDDEN (__fini_array_end = .);
. = ALIGN(8);
} >FLASH
/* used by the startup to initialize data */
_sidata = LOADADDR(.data);
/* Initialized data sections goes into RAM, load LMA copy after code */
.data :
{
. = ALIGN(8);
_sdata = .; /* create a global symbol at data start */
*(.data) /* .data sections */
*(.data*) /* .data* sections */
. = ALIGN(8);
_edata = .; /* define a global symbol at data end */
} >RAM AT> FLASH
/* Uninitialized data section */
. = ALIGN(4);
.bss :
{
/* This is used by the startup in order to initialize the .bss secion */
_sbss = .; /* define a global symbol at bss start */
__bss_start__ = _sbss;
*(.bss)
*(.bss*)
*(COMMON)
. = ALIGN(4);
_ebss = .; /* define a global symbol at bss end */
__bss_end__ = _ebss;
} >RAM
/* User_heap_stack section, used to check that there is enough RAM left */
._user_heap_stack :
{
. = ALIGN(8);
PROVIDE ( end = . );
PROVIDE ( _end = . );
. = . + _Min_Heap_Size;
. = . + _Min_Stack_Size;
. = ALIGN(8);
} >RAM
/* Remove information from the standard libraries */
/DISCARD/ :
{
libc.a ( * )
libm.a ( * )
libgcc.a ( * )
}
.ARM.attributes 0 : { *(.ARM.attributes) }
}
Вот линкерскрипт для микроконтроллера STM32F767ZI:
/*
*****************************************************************************
**
** File : LinkerScript.ld
**
** Abstract : Linker script for STM32F767ZITx Device with
** 2048KByte FLASH, 512KByte RAM
**
** Set heap size, stack size and stack location according
** to application requirements.
**
** Set memory bank area and size if external memory is used.
**
** Target : STMicroelectronics STM32
**
**
** Distribution: The file is distributed as is, without any warranty
** of any kind.
**
*****************************************************************************
** @attention
**
** <h2><center>© COPYRIGHT(c) 2014 Ac6</center></h2>
**
** Redistribution and use in source and binary forms, with or without modification,
** are permitted provided that the following conditions are met:
** 1. Redistributions of source code must retain the above copyright notice,
** this list of conditions and the following disclaimer.
** 2. Redistributions in binary form must reproduce the above copyright notice,
** this list of conditions and the following disclaimer in the documentation
** and/or other materials provided with the distribution.
** 3. Neither the name of Ac6 nor the names of its contributors
** may be used to endorse or promote products derived from this software
** without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
** AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
** DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
** SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
** OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
**
*****************************************************************************
*/
/* Entry Point */
ENTRY(Reset_Handler)
/* Highest address of the user mode stack */
_estack = 0x20080000; /* end of RAM */
/* Generate a link error if heap and stack don't fit into RAM */
_Min_Heap_Size = 0x200; /* required amount of heap */
_Min_Stack_Size = 0x400; /* required amount of stack */
/* Specify the memory areas */
MEMORY
{
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 512K
FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 2048K
}
/* Define output sections */
SECTIONS
{
/* The startup code goes first into FLASH */
.isr_vector :
{
. = ALIGN(4);
KEEP(*(.isr_vector)) /* Startup code */
. = ALIGN(4);
} >FLASH
/* The program code and other data goes into FLASH */
.text :
{
. = ALIGN(4);
*(.text) /* .text sections (code) */
*(.text*) /* .text* sections (code) */
*(.glue_7) /* glue arm to thumb code */
*(.glue_7t) /* glue thumb to arm code */
*(.eh_frame)
KEEP (*(.init))
KEEP (*(.fini))
. = ALIGN(4);
_etext = .; /* define a global symbols at end of code */
} >FLASH
/* Constant data goes into FLASH */
.rodata :
{
. = ALIGN(4);
*(.rodata) /* .rodata sections (constants, strings, etc.) */
*(.rodata*) /* .rodata* sections (constants, strings, etc.) */
. = ALIGN(4);
} >FLASH
.ARM.extab : { *(.ARM.extab* .gnu.linkonce.armextab.*) } >FLASH
.ARM : {
__exidx_start = .;
*(.ARM.exidx*)
__exidx_end = .;
} >FLASH
.preinit_array :
{
PROVIDE_HIDDEN (__preinit_array_start = .);
KEEP (*(.preinit_array*))
PROVIDE_HIDDEN (__preinit_array_end = .);
} >FLASH
.init_array :
{
PROVIDE_HIDDEN (__init_array_start = .);
KEEP (*(SORT(.init_array.*)))
KEEP (*(.init_array*))
PROVIDE_HIDDEN (__init_array_end = .);
} >FLASH
.fini_array :
{
PROVIDE_HIDDEN (__fini_array_start = .);
KEEP (*(SORT(.fini_array.*)))
KEEP (*(.fini_array*))
PROVIDE_HIDDEN (__fini_array_end = .);
} >FLASH
/* used by the startup to initialize data */
_sidata = LOADADDR(.data);
/* Initialized data sections goes into RAM, load LMA copy after code */
.data :
{
. = ALIGN(4);
_sdata = .; /* create a global symbol at data start */
*(.data) /* .data sections */
*(.data*) /* .data* sections */
. = ALIGN(4);
_edata = .; /* define a global symbol at data end */
} >RAM AT> FLASH
/* Uninitialized data section */
. = ALIGN(4);
.bss :
{
/* This is used by the startup in order to initialize the .bss secion */
_sbss = .; /* define a global symbol at bss start */
__bss_start__ = _sbss;
*(.bss)
*(.bss*)
*(COMMON)
. = ALIGN(4);
_ebss = .; /* define a global symbol at bss end */
__bss_end__ = _ebss;
} >RAM
/* User_heap_stack section, used to check that there is enough RAM left */
._user_heap_stack :
{
. = ALIGN(8);
PROVIDE ( end = . );
PROVIDE ( _end = . );
. = . + _Min_Heap_Size;
. = . + _Min_Stack_Size;
. = ALIGN(8);
} >RAM
/* Remove information from the standard libraries */
/DISCARD/ :
{
libc.a ( * )
libm.a ( * )
libgcc.a ( * )
}
.ARM.attributes 0 : { *(.ARM.attributes) }
}
1 ответ
Не сравнивайте плохо написанные линкерные скрипты.
Большая часть этого не имеет никакого смысла:
.isr_vectors должен быть выровнен на 512, как того требует SCB->VTOR. Большинство приложений помещают векторную таблицу в начале FLASH/RAM - и это местоположение в любом случае выравнивается по 512:)
Остальное (кроме стека, который может потребоваться для механизма ввода прерываний для выравнивания по 8 байтов - но в этом семействе UC по умолчанию (состояние сброса регистров конфигурации ядра) это не требуется), это просто воображение человека кто это написал. Они должны быть выровнены на 4 байта, чтобы избежать снижения производительности, так как эти микросхемы допускают неравномерный доступ.
Некоторые люди говорят, что шины имеют ширину 64 (или 128) бит, и такое выравнивание может оказать положительное влияние на производительность, но оно незначительно, если таковые имеются.
Если у вас есть доступ к памяти DMA, хорошо выровнять ее, чтобы избежать состояний ожидания.
Некоторые другие ядра Cotex не допускают выравнивания доступа.
PS Помните, что некоторые области памяти (в документации под названием "Тип памяти устройства" должны быть естественно выровнены - что означает 4 байта в 32-битных системах)