use specific memory section memory to link a variable

Candice1 — Wed, 16 Feb 2022 11:28:19 GMT

I'm having trouble in setting the section attribute of gcc to define that a variable should reside in a specific memory section instead of the default.

I'm using the arm cortex m3 LPC1759. I got the link files from LPCXpresso IDE, but I don't use it, I have my own makefile. The link files are:

Generic link file

INCLUDE "./link/LPCmem.ld" /* see below */ ENTRY(ResetISR) SECTIONS { /* MAIN TEXT SECTION */ .text : ALIGN(4) { FILL(0xff) __vectors_start__ = ABSOLUTE(.) ; KEEP(*(.isr_vector)) /* Global Section Table */ . = ALIGN(4) ; __section_table_start = .; __data_section_table = .; LONG(LOADADDR(.data)); LONG( ADDR(.data)); LONG( SIZEOF(.data)); LONG(LOADADDR(.data_RAM2)); LONG( ADDR(.data_RAM2)); LONG( SIZEOF(.data_RAM2)); __data_section_table_end = .; __bss_section_table = .; LONG( ADDR(.bss)); LONG( SIZEOF(.bss)); LONG( ADDR(.bss_RAM2)); LONG( SIZEOF(.bss_RAM2)); __bss_section_table_end = .; __section_table_end = . ; /* End of Global Section Table */ *(.after_vectors*) } >FLASH .text : ALIGN(4) { *(.text*) *(.rodata .rodata.* .constdata .constdata.*) . = ALIGN(4); } > FLASH /* * for exception handling/unwind - some Newlib functions (in common * with C++ and STDC++) use this. */ .ARM.extab : ALIGN(4) { *(.ARM.extab* .gnu.linkonce.armextab.*) } > FLASH __exidx_start = .; .ARM.exidx : ALIGN(4) { *(.ARM.exidx* .gnu.linkonce.armexidx.*) } > FLASH __exidx_end = .; _etext = .; /* DATA section for SRAM0 */ .data_RAM2 : ALIGN(4) { FILL(0xff) *(.ramfunc.$RAM2) *(.ramfunc.$SRAM0) *(.data.$RAM2*) *(.data.$SRAM0*) . = ALIGN(4) ; } > SRAM0 AT>FLASH /* MAIN DATA SECTION */ .uninit_RESERVED : ALIGN(4) { KEEP(*(.bss.$RESERVED*)) . = ALIGN(4) ; _end_uninit_RESERVED = .; } > SRAM /* Main DATA section (SRAM) */ .data : ALIGN(4) { FILL(0xff) _data = . ; *(vtable) *(.ramfunc*) *(.data*) . = ALIGN(4) ; _edata = . ; } > SRAM AT>FLASH /* BSS section for SRAM0 */ .bss_RAM2 : ALIGN(4) { *(.bss.$RAM2*) *(.bss.$SRAM0*) . = ALIGN(4) ; } > SRAM0 /* MAIN BSS SECTION */ .bss : ALIGN(4) { _bss = .; *(.bss*) *(COMMON) . = ALIGN(4) ; _ebss = .; PROVIDE(end = .); } > SRAM /* NOINIT section for SRAM0 */ .noinit_RAM2 (NOLOAD) : ALIGN(4) { *(.noinit.$RAM2*) *(.noinit.$SRAM0*) . = ALIGN(4) ; } > SRAM0 /* DEFAULT NOINIT SECTION */ .noinit (NOLOAD): ALIGN(4) { _noinit = .; *(.noinit*) . = ALIGN(4) ; _end_noinit = .; } > SRAM PROVIDE(_pvHeapStart = .); PROVIDE(_vStackTop = __top_SRAM - 0); }

Memory definition file

/* Define each memory region */ MEMORY { FLASH (rx) : ORIGIN = 0x0, LENGTH = 0x80000 /* 512K bytes */ SRAM (rwx) : ORIGIN = 0x10000000, LENGTH = 0x8000 /* 32K bytes */ SRAM0 (rwx) : ORIGIN = 0x2007c000, LENGTH = 0x8000 /* 32K bytes */ } /* Define a symbol for the top of each memory region */ __top_FLASH = 0x0 + 0x80000; __top_SRAM = 0x10000000 + 0x8000; __top_SRAM0 = 0x2007c000 + 0x8000;

Above is the LPCmem.ld file included in the previous file.

I'm forcing the freertos heap variable to be in the custom section, like this:

static unsigned char ucHeap[ configTOTAL_HEAP_SIZE ] __attribute__((section(".data_RAM2")));

The linking of objects files are done without errors, but the variable isn't placed in the right memory position, how I could check with nm command:

... 10000028 d ucHeap 10002028 d uxCriticalNesting ...

I try to change the section to another that doesn't exist, just to check if the linker verifies the names, and apparently, it doesn't.

Re: use specific memory section memory to link a variable

ZhangJennie — Fri, 18 Feb 2022 07:58:59 GMT

Hi Candice1

Please check if this article can help you

https://community.nxp.com/t5/LPC-Microcontrollers-Knowledge/LPC-How-to-place-data-function-file-in-specified-memory-under/ta-p/1316392

Have a nice day

Jun Zhang

LPCXpresso IDE中的主题 use specific memory section memory to link a variable

use specific memory section memory to link a variable

Generic link file

Memory definition file

Re: use specific memory section memory to link a variable