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286 changes: 286 additions & 0 deletions src/rp2_common/pico_crt0/rp2040/memmap_flash.template.ld
Original file line number Diff line number Diff line change
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/* Based on GCC ARM embedded samples.
Defines the following symbols for use by code:
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There are a load of double-underscore identifiers (e.g. __logical_binary_start, __embedded_block_end, __binary_info_start) which aren't included in this list. Should they be? 🤷 (I know almost nothing about linker scripts)

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This is an identical copy of memmap_default.ld, so changing anything other than the memory regions is outside the scope of this PR - maybe worth pinging @kilograham about tidying up the linker scripts?

__exidx_start
__exidx_end
__etext
__data_start__
__preinit_array_start
__preinit_array_end
__init_array_start
__init_array_end
__fini_array_start
__fini_array_end
__data_end__
__bss_start__
__bss_end__
__end__
end
__HeapLimit
__StackLimit
__StackTop
__stack (== StackTop)
*/

MEMORY
{
INCLUDE "pico_flash_region.ld"
RAM(rwx) : ORIGIN = @RAM_ORIGIN@, LENGTH = @RAM_LENGTH@
SCRATCH_X(rwx) : ORIGIN = @SCRATCH_X_ORIGIN@, LENGTH = @SCRATCH_X_LENGTH@
SCRATCH_Y(rwx) : ORIGIN = @SCRATCH_Y_ORIGIN@, LENGTH = @SCRATCH_Y_LENGTH@
}

ENTRY(_entry_point)

SECTIONS
{
/* Second stage bootloader is prepended to the image. It must be 256 bytes big
and checksummed. It is usually built by the boot_stage2 target
in the Raspberry Pi Pico SDK
*/

.flash_begin : {
__flash_binary_start = .;
} > FLASH

.boot2 : {
__boot2_start__ = .;
KEEP (*(.boot2))
__boot2_end__ = .;
} > FLASH

ASSERT(__boot2_end__ - __boot2_start__ == 256,
"ERROR: Pico second stage bootloader must be 256 bytes in size")

/* The second stage will always enter the image at the start of .text.
The debugger will use the ELF entry point, which is the _entry_point
symbol if present, otherwise defaults to start of .text.
This can be used to transfer control back to the bootrom on debugger
launches only, to perform proper flash setup.
*/

.text : {
__logical_binary_start = .;
KEEP (*(.vectors))
KEEP (*(.binary_info_header))
__binary_info_header_end = .;
KEEP (*(.embedded_block))
__embedded_block_end = .;
KEEP (*(.reset))
/* TODO revisit this now memset/memcpy/float in ROM */
/* bit of a hack right now to exclude all floating point and time critical (e.g. memset, memcpy) code from
* FLASH ... we will include any thing excluded here in .data below by default */
*(.init)
*(EXCLUDE_FILE(*libgcc.a: *libc.a:*lib_a-mem*.o *libm.a:) .text*)
*(.fini)
/* Pull all c'tors into .text */
*crtbegin.o(.ctors)
*crtbegin?.o(.ctors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors)
*(SORT(.ctors.*))
*(.ctors)
/* Followed by destructors */
*crtbegin.o(.dtors)
*crtbegin?.o(.dtors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .dtors)
*(SORT(.dtors.*))
*(.dtors)

. = ALIGN(4);
/* preinit data */
PROVIDE_HIDDEN (__preinit_array_start = .);
KEEP(*(SORT(.preinit_array.*)))
KEEP(*(.preinit_array))
PROVIDE_HIDDEN (__preinit_array_end = .);

. = ALIGN(4);
/* init data */
PROVIDE_HIDDEN (__init_array_start = .);
KEEP(*(SORT(.init_array.*)))
KEEP(*(.init_array))
PROVIDE_HIDDEN (__init_array_end = .);

. = ALIGN(4);
/* finit data */
PROVIDE_HIDDEN (__fini_array_start = .);
*(SORT(.fini_array.*))
*(.fini_array)
PROVIDE_HIDDEN (__fini_array_end = .);

*(.eh_frame*)
. = ALIGN(4);
} > FLASH

.rodata : {
*(EXCLUDE_FILE(*libgcc.a: *libc.a:*lib_a-mem*.o *libm.a:) .rodata*)
. = ALIGN(4);
*(SORT_BY_ALIGNMENT(SORT_BY_NAME(.flashdata*)))
. = ALIGN(4);
} > FLASH

.ARM.extab :
{
*(.ARM.extab* .gnu.linkonce.armextab.*)
} > FLASH

__exidx_start = .;
.ARM.exidx :
{
*(.ARM.exidx* .gnu.linkonce.armexidx.*)
} > FLASH
__exidx_end = .;

/* Machine inspectable binary information */
. = ALIGN(4);
__binary_info_start = .;
.binary_info :
{
KEEP(*(.binary_info.keep.*))
*(.binary_info.*)
} > FLASH
__binary_info_end = .;
. = ALIGN(4);

.ram_vector_table (NOLOAD): {
*(.ram_vector_table)
} > RAM

.uninitialized_data (NOLOAD): {
. = ALIGN(4);
*(.uninitialized_data*)
} > RAM

.data : {
__data_start__ = .;
*(vtable)

*(.time_critical*)

/* remaining .text and .rodata; i.e. stuff we exclude above because we want it in RAM */
*(.text*)
. = ALIGN(4);
*(.rodata*)
. = ALIGN(4);

*(.data*)

. = ALIGN(4);
*(.after_data.*)
. = ALIGN(4);
/* preinit data */
PROVIDE_HIDDEN (__mutex_array_start = .);
KEEP(*(SORT(.mutex_array.*)))
KEEP(*(.mutex_array))
PROVIDE_HIDDEN (__mutex_array_end = .);

. = ALIGN(4);
*(.jcr)
. = ALIGN(4);
} > RAM AT> FLASH

.tdata : {
. = ALIGN(4);
*(.tdata .tdata.* .gnu.linkonce.td.*)
/* All data end */
__tdata_end = .;
} > RAM AT> FLASH
PROVIDE(__data_end__ = .);

/* __etext is (for backwards compatibility) the name of the .data init source pointer (...) */
__etext = LOADADDR(.data);

.tbss (NOLOAD) : {
. = ALIGN(4);
__bss_start__ = .;
__tls_base = .;
*(.tbss .tbss.* .gnu.linkonce.tb.*)
*(.tcommon)

__tls_end = .;
} > RAM

.bss (NOLOAD) : {
. = ALIGN(4);
__tbss_end = .;

*(SORT_BY_ALIGNMENT(SORT_BY_NAME(.bss*)))
*(COMMON)
. = ALIGN(4);
__bss_end__ = .;
} > RAM

.heap (NOLOAD):
{
__end__ = .;
end = __end__;
KEEP(*(.heap*))
} > RAM
/* historically on GCC sbrk was growing past __HeapLimit to __StackLimit, however
to be more compatible, we now set __HeapLimit explicitly to where the end of the heap is */
__HeapLimit = ORIGIN(RAM) + LENGTH(RAM);

/* Start and end symbols must be word-aligned */
.scratch_x : {
__scratch_x_start__ = .;
*(.scratch_x.*)
. = ALIGN(4);
__scratch_x_end__ = .;
} > SCRATCH_X AT > FLASH
__scratch_x_source__ = LOADADDR(.scratch_x);

.scratch_y : {
__scratch_y_start__ = .;
*(.scratch_y.*)
. = ALIGN(4);
__scratch_y_end__ = .;
} > SCRATCH_Y AT > FLASH
__scratch_y_source__ = LOADADDR(.scratch_y);

/* .stack*_dummy section doesn't contains any symbols. It is only
* used for linker to calculate size of stack sections, and assign
* values to stack symbols later
*
* stack1 section may be empty/missing if platform_launch_core1 is not used */

/* by default we put core 0 stack at the end of scratch Y, so that if core 1
* stack is not used then all of SCRATCH_X is free.
*/
.stack1_dummy (NOLOAD):
{
*(.stack1*)
} > SCRATCH_X
.stack_dummy (NOLOAD):
{
KEEP(*(.stack*))
} > SCRATCH_Y

.flash_end : {
KEEP(*(.embedded_end_block*))
PROVIDE(__flash_binary_end = .);
} > FLASH

/* stack limit is poorly named, but historically is maximum heap ptr */
__StackLimit = ORIGIN(RAM) + LENGTH(RAM);
__StackOneTop = ORIGIN(SCRATCH_X) + LENGTH(SCRATCH_X);
__StackTop = ORIGIN(SCRATCH_Y) + LENGTH(SCRATCH_Y);
__StackOneBottom = __StackOneTop - SIZEOF(.stack1_dummy);
__StackBottom = __StackTop - SIZEOF(.stack_dummy);
PROVIDE(__stack = __StackTop);

/* picolibc and LLVM */
PROVIDE (__heap_start = __end__);
PROVIDE (__heap_end = __HeapLimit);
PROVIDE( __tls_align = MAX(ALIGNOF(.tdata), ALIGNOF(.tbss)) );
PROVIDE( __tls_size_align = (__tls_size + __tls_align - 1) & ~(__tls_align - 1));
PROVIDE( __arm32_tls_tcb_offset = MAX(8, __tls_align) );

/* llvm-libc */
PROVIDE (_end = __end__);
PROVIDE (__llvm_libc_heap_limit = __HeapLimit);

/* Check if data + heap + stack exceeds RAM limit */
ASSERT(__StackLimit >= __HeapLimit, "region RAM overflowed")

ASSERT( __binary_info_header_end - __logical_binary_start <= 256, "Binary info must be in first 256 bytes of the binary")
/* todo assert on extra code */
}

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