esp-idf/components/esp_system/ld/ld.flash.sections

#include "sdkconfig.h"
#include "ld.common"

  .flash.text :
  {
    _stext = .;

    /**
     * Mark the start of flash.text.
     * This can be used by the MMU driver to maintain the virtual address.
     */
    _instruction_reserved_start = ABSOLUTE(.);
    _text_start = ABSOLUTE(.);

    SECTION_MAPPINGS_WITH_PADDING(flash_text)

    *(.stub)
    *(.gnu.linkonce.t.*)
    *(.gnu.warning)
    *(.irom0.text) /* catch stray ICACHE_RODATA_ATTR */

    /**
     * CPU will try to prefetch up to 16 bytes of instructions.
     * This means that any configuration (e.g. MMU, PMS) must allow
     * safe access to up to 16 bytes after the last real instruction.
     * Add dummy bytes to ensure this.
     */
    . += _esp_flash_mmap_prefetch_pad_size;

#if CONFIG_SPIRAM_FETCH_INSTRUCTIONS && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
    /**
     * Align the end of flash text region as per PMP granularity to allow using the
     * page alignment gap created while mapping the flash region into the PSRAM memory.
     */
    . = ALIGN(_esp_pmp_align_size);
#endif // CONFIG_SPIRAM_FETCH_INSTRUCTIONS && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION

    _text_end = ABSOLUTE(.);

    /**
     * Mark the flash.text end.
     * This can be used for MMU driver to maintain virtual address.
     */
    _instruction_reserved_end = ABSOLUTE(.);
    _etext = .;

    /**
     * Similar to _iram_start, this symbol goes here so it is
     * resolved by addr2line in preference to the first symbol in
     * the flash.text segment.
     */
    _flash_cache_start = ABSOLUTE(0);
  } > flash_text_seg

  /**
   * Dummy section represents the .flash.text section but in flash_rodata_seg.
   * Thus, it must have its alignment and (at least) its size.
   */
  .flash_rodata_dummy (NOLOAD) :
  {
    _flash_rodata_dummy_start = .;

    . = ALIGN(ALIGNOF(.flash.text)) + SIZEOF(.flash.text);

    /* Add alignment of MMU page size + 0x20 bytes for the mapping header */
    . = ALIGN(_esp_mmu_page_size) + 0x20;
  } > flash_rodata_seg

  .flash.appdesc : ALIGN(0x10)
  {
    /**
     * Mark flash.rodata start.
     * This can be used for MMU driver to maintain virtual address.
     */
    _rodata_reserved_start = ABSOLUTE(.);
    _rodata_start = ABSOLUTE(.);

    /* !DO NOT PUT ANYTHING BEFORE THIS! */

    /* Should be the first: App version info */
    *(.rodata_desc .rodata_desc.*)

    /* Should be the second: Custom app version info */
    *(.rodata_custom_desc .rodata_custom_desc.*)

    /**
     * Create an empty gap within this section. Thanks to this, the end of this
     * section will match .flash.rodata's begin address. Thus, both sections
     * will be merged when creating the final bin image.
     */
    . = ALIGN(ALIGNOF(.flash.rodata));
  } > flash_rodata_seg
  ASSERT_SECTIONS_GAP(.flash.appdesc, .flash.rodata)

  .flash.rodata : ALIGN(0x10)
  {
    _flash_rodata_start = ABSOLUTE(.);

    SECTION_MAPPINGS_WITH_PADDING(flash_rodata)

#if CONFIG_LIBC_PICOLIBC
    *(.got .got.plt) /* TODO: GCC-439 */
#endif
    *(.irom1.text) /* catch stray ICACHE_RODATA_ATTR */
    *(.gnu.linkonce.r.*)
    *(.rodata1)

    *(.gcc_except_table .gcc_except_table.*)
    *(.gnu.linkonce.e.*)

    . = ALIGN(ALIGNOF(.flash.init_array));
  } > flash_rodata_seg
  ASSERT_SECTIONS_GAP(.flash.rodata, .flash.init_array)

  .flash.init_array :
  {
    /**
     * C++ constructor tables.
     *
     * Excluding crtbegin.o/crtend.o since IDF doesn't use the toolchain crt.
     */
    ALIGNED_SYMBOL(4, __preinit_array_start)
    ALIGNED_SYMBOL(4, __bothinit_array_start)
    KEEP (*(.preinit_array))
    __preinit_array_end = ABSOLUTE(.);
    ALIGNED_SYMBOL(4, __init_array_start)
    KEEP (*(SORT_BY_INIT_PRIORITY(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array.*)))
    KEEP (*(EXCLUDE_FILE (*crtend.* *crtbegin.*) .init_array))
    __init_array_end = ABSOLUTE(.);
    __bothinit_array_end = ABSOLUTE(.);

    /* Addresses of memory regions reserved via SOC_RESERVE_MEMORY_REGION() */
    ALIGNED_SYMBOL(4, soc_reserved_memory_region_start)
    KEEP (*(.reserved_memory_address))
    soc_reserved_memory_region_end = ABSOLUTE(.);

    /* System init functions registered via ESP_SYSTEM_INIT_FN */
    ALIGNED_SYMBOL(4, _esp_sys_init_fn_start)
    KEEP (*(SORT_BY_INIT_PRIORITY(.esp_sys_init_fn.*)))
    _esp_sys_init_fn_end = ABSOLUTE(.);

    _rodata_end = ABSOLUTE(.);
    . = ALIGN(ALIGNOF(SECTION_AFTER_FLASH_RODATA));
  } > flash_rodata_seg
  ASSERT_SECTIONS_GAP(.flash.init_array, SECTION_AFTER_FLASH_RODATA)

#if EH_FRAME_LINKING_ENABLED
  .eh_frame_hdr :
  {
    ALIGNED_SYMBOL(4, __eh_frame_hdr)

    KEEP (*(.eh_frame_hdr))

    __eh_frame_hdr_end = ABSOLUTE(.);

    . = ALIGN(ALIGNOF(.eh_frame));
  } > flash_rodata_seg
  ASSERT_SECTIONS_GAP(.eh_frame_hdr, .eh_frame)

  .eh_frame :
  {
    ALIGNED_SYMBOL(4, __eh_frame)

    KEEP (*(.eh_frame))

    /**
     * As we are not linking with crtend.o, which includes the CIE terminator
     * (see __FRAME_END__ in libgcc sources), it is manually provided here.
     */
    LONG(0);

    __eh_frame_end = ABSOLUTE(.);

    . = ALIGN(ALIGNOF(.flash.tdata));
  } > flash_rodata_seg
  ASSERT_SECTIONS_GAP(.eh_frame, .flash.tdata)
#if CONFIG_ESP_SYSTEM_USE_EH_FRAME
  ASSERT((__eh_frame_hdr_end > __eh_frame_hdr), "eh_frame_hdr size is 0")
  ASSERT((__eh_frame_end > __eh_frame), "eh_frame size is 0")
#endif // CONFIG_ESP_SYSTEM_USE_EH_FRAME
#endif // EH_FRAME_LINKING_ENABLED

  .flash.tdata :
  {
    /**
     * IMPORTANT: Keep tdata and tbss sections contiguous (no gaps between them).
     * The TLS runtime code calculates offsets assuming these sections are
     * adjacent. Gaps would cause incorrect address calculations, leading
     * to accessing wrong memory.
     */

    /* Thread-local data sections */
    _thread_local_data_start = ABSOLUTE(.);

#if CONFIG_LIBC_PICOLIBC
    _picolibc_reent_stub_start = ABSOLUTE(.);
    KEEP(*(.tdata.errno))

#if CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY
    /* Reproduce the public fields from struct _reent */
    KEEP(*(.tdata.tls_stdin))
    KEEP(*(.tdata.tls_stdout))
    KEEP(*(.tdata.tls_stderr))
#endif // CONFIG_LIBC_PICOLIBC_NEWLIB_COMPATIBILITY

    _picolibc_reent_stub_end = ABSOLUTE(.);
#endif // CONFIG_LIBC_PICOLIBC

    *(.tdata .tdata.* .gnu.linkonce.td.*)

    . = ALIGN(ALIGNOF(.flash.tbss));
    _thread_local_data_end = ABSOLUTE(.);
  } > flash_rodata_seg
  ASSERT_SECTIONS_GAP(.flash.tdata, .flash.tbss)
  ASSERT_PICOLIBC_REENT_STUB()

  .flash.tbss (NOLOAD) :
  {
    /* Thread-local BSS sections */
    _thread_local_bss_start = ABSOLUTE(.);
    *(.tbss .tbss.* .gnu.linkonce.tb.*)
    *(.tcommon .tcommon.*)
    _thread_local_bss_end = ABSOLUTE(.);
  } > flash_rodata_seg
  ASSERT(_thread_local_data_end == _thread_local_bss_start,
         "tdata and tbss must be contiguous.")

  /**
   * This section contains all the rodata that is not used at runtime,
   * helping to avoid an increase in binary size.
   */
  .flash.rodata_noload (NOLOAD) :
  {
#if CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
    /**
     * Align the end of flash rodata region as per PMP granularity to allow using the
     * page alignment gap created while mapping the flash region into the PSRAM memory.
     */
    . = ALIGN(_esp_pmp_align_size);
#endif // CONFIG_SPIRAM_RODATA && CONFIG_SPIRAM_PRE_CONFIGURE_MEMORY_PROTECTION
    /**
     * This symbol marks the end of flash.rodata. It can be utilized by the MMU
     * driver to maintain the virtual address.
     * NOLOAD rodata may not be included in this section.
     */
    _rodata_reserved_end = .;

    SECTION_MAPPINGS(rodata_noload)
  } > flash_rodata_seg

#if CONFIG_APP_BUILD_USE_FLASH_SECTIONS
  /**
   * If rodata default segment is placed in `flash_rodata_seg`, then flash's first
   * rodata section must also be first in the segment.
   */
  ASSERT(_flash_rodata_dummy_start == ORIGIN(flash_rodata_seg),
         ".flash_rodata_dummy section must be placed at the beginning of the rodata segment.")
#endif