embassy/tests/stm32/link_ram.x

/* ##### EMBASSY NOTE
    Originally from https://github.com/rust-embedded/cortex-m-rt/blob/master/link.x.in
    Adjusted to put everything in RAM
*/

/* # Developer notes

- Symbols that start with a double underscore (__) are considered "private"

- Symbols that start with a single underscore (_) are considered "semi-public"; they can be
  overridden in a user linker script, but should not be referred from user code (e.g. `extern "C" {
  static mut __sbss }`).

- `EXTERN` forces the linker to keep a symbol in the final binary. We use this to make sure a
  symbol if not dropped if it appears in or near the front of the linker arguments and "it's not
  needed" by any of the preceding objects (linker arguments)

- `PROVIDE` is used to provide default values that can be overridden by a user linker script

- On alignment: it's important for correctness that the VMA boundaries of both .bss and .data *and*
  the LMA of .data are all 4-byte aligned. These alignments are assumed by the RAM initialization
  routine. There's also a second benefit: 4-byte aligned boundaries means that you won't see
  "Address (..) is out of bounds" in the disassembly produced by `objdump`.
*/

/* Provides information about the memory layout of the device */
/* This will be provided by the user (see `memory.x`) or by a Board Support Crate */
INCLUDE memory.x

/* # Entry point = reset vector */
EXTERN(__RESET_VECTOR);
EXTERN(Reset);
ENTRY(Reset);

/* # Exception vectors */
/* This is effectively weak aliasing at the linker level */
/* The user can override any of these aliases by defining the corresponding symbol themselves (cf.
   the `exception!` macro) */
EXTERN(__EXCEPTIONS); /* depends on all the these PROVIDED symbols */

EXTERN(DefaultHandler);

PROVIDE(NonMaskableInt = DefaultHandler);
EXTERN(HardFaultTrampoline);
PROVIDE(MemoryManagement = DefaultHandler);
PROVIDE(BusFault = DefaultHandler);
PROVIDE(UsageFault = DefaultHandler);
PROVIDE(SecureFault = DefaultHandler);
PROVIDE(SVCall = DefaultHandler);
PROVIDE(DebugMonitor = DefaultHandler);
PROVIDE(PendSV = DefaultHandler);
PROVIDE(SysTick = DefaultHandler);

PROVIDE(DefaultHandler = DefaultHandler_);
PROVIDE(HardFault = HardFault_);

/* # Interrupt vectors */
EXTERN(__INTERRUPTS); /* `static` variable similar to `__EXCEPTIONS` */

/* # Pre-initialization function */
/* If the user overrides this using the `pre_init!` macro or by creating a `__pre_init` function,
   then the function this points to will be called before the RAM is initialized. */
PROVIDE(__pre_init = DefaultPreInit);

/* # Sections */
SECTIONS
{
  PROVIDE(_stack_start = ORIGIN(RAM) + LENGTH(RAM));

  /* ## Sections in RAM */
  /* ### Vector table */
  .vector_table ORIGIN(RAM) :
  {
    /* Initial Stack Pointer (SP) value */
    LONG(_stack_start);

    /* Reset vector */
    KEEP(*(.vector_table.reset_vector)); /* this is the `__RESET_VECTOR` symbol */
    __reset_vector = .;

    /* Exceptions */
    KEEP(*(.vector_table.exceptions)); /* this is the `__EXCEPTIONS` symbol */
    __eexceptions = .;

    /* Device specific interrupts */
    KEEP(*(.vector_table.interrupts)); /* this is the `__INTERRUPTS` symbol */
  } > RAM

  PROVIDE(_stext = ADDR(.vector_table) + SIZEOF(.vector_table));

  /* ### .text */
  .text _stext :
  {
    __stext = .;
    *(.Reset);

    *(.text .text.*);

    /* The HardFaultTrampoline uses the `b` instruction to enter `HardFault`,
       so must be placed close to it. */
    *(.HardFaultTrampoline);
    *(.HardFault.*);

    . = ALIGN(4); /* Pad .text to the alignment to workaround overlapping load section bug in old lld */
    __etext = .;
  } > RAM

  /* ### .rodata */
  .rodata : ALIGN(4)
  {
    . = ALIGN(4);
    __srodata = .;
    *(.rodata .rodata.*);

    /* 4-byte align the end (VMA) of this section.
       This is required by LLD to ensure the LMA of the following .data
       section will have the correct alignment. */
    . = ALIGN(4);
    __erodata = .;
  } > RAM

  /* ## Sections in RAM */
  /* ### .data */
  .data : ALIGN(4)
  {
    . = ALIGN(4);
    __sdata = .;
    *(.data .data.*);
    . = ALIGN(4); /* 4-byte align the end (VMA) of this section */
  } > RAM
  /* Allow sections from user `memory.x` injected using `INSERT AFTER .data` to
   * use the .data loading mechanism by pushing __edata. Note: do not change
   * output region or load region in those user sections! */
  . = ALIGN(4);
  __edata = .;

  /* LMA of .data */
  __sidata = LOADADDR(.data);

  /* ### .gnu.sgstubs
     This section contains the TrustZone-M veneers put there by the Arm GNU linker. */
  /* Security Attribution Unit blocks must be 32 bytes aligned. */
  /* Note that this pads the RAM usage to 32 byte alignment. */
  .gnu.sgstubs : ALIGN(32)
  {
    . = ALIGN(32);
    __veneer_base = .;
    *(.gnu.sgstubs*)
    . = ALIGN(32);
    __veneer_limit = .;
  } > RAM

  /* ### .bss */
  .bss (NOLOAD) : ALIGN(4)
  {
    . = ALIGN(4);
    __sbss = .;
    *(.bss .bss.*);
    *(COMMON); /* Uninitialized C statics */
    . = ALIGN(4); /* 4-byte align the end (VMA) of this section */
  } > RAM
  /* Allow sections from user `memory.x` injected using `INSERT AFTER .bss` to
   * use the .bss zeroing mechanism by pushing __ebss. Note: do not change
   * output region or load region in those user sections! */
  . = ALIGN(4);
  __ebss = .;

  /* ### .uninit */
  .uninit (NOLOAD) : ALIGN(4)
  {
    . = ALIGN(4);
    __suninit = .;
    *(.uninit .uninit.*);
    . = ALIGN(4);
    __euninit = .;
  } > RAM

  /* Place the heap right after `.uninit` in RAM */
  PROVIDE(__sheap = __euninit);

  /* ## .got */
  /* Dynamic relocations are unsupported. This section is only used to detect relocatable code in
     the input files and raise an error if relocatable code is found */
  .got (NOLOAD) :
  {
    KEEP(*(.got .got.*));
  }

  /* ## Discarded sections */
  /DISCARD/ :
  {
    /* Unused exception related info that only wastes space */
    *(.ARM.exidx);
    *(.ARM.exidx.*);
    *(.ARM.extab.*);
  }
}

/* Do not exceed this mark in the error messages below                                    | */
/* # Alignment checks */
ASSERT(ORIGIN(RAM) % 4 == 0, "
ERROR(cortex-m-rt): the start of the RAM region must be 4-byte aligned");

ASSERT(__sdata % 4 == 0 && __edata % 4 == 0, "
BUG(cortex-m-rt): .data is not 4-byte aligned");

ASSERT(__sidata % 4 == 0, "
BUG(cortex-m-rt): the LMA of .data is not 4-byte aligned");

ASSERT(__sbss % 4 == 0 && __ebss % 4 == 0, "
BUG(cortex-m-rt): .bss is not 4-byte aligned");

ASSERT(__sheap % 4 == 0, "
BUG(cortex-m-rt): start of .heap is not 4-byte aligned");

/* # Position checks */

/* ## .vector_table */
ASSERT(__reset_vector == ADDR(.vector_table) + 0x8, "
BUG(cortex-m-rt): the reset vector is missing");

ASSERT(__eexceptions == ADDR(.vector_table) + 0x40, "
BUG(cortex-m-rt): the exception vectors are missing");

ASSERT(SIZEOF(.vector_table) > 0x40, "
ERROR(cortex-m-rt): The interrupt vectors are missing.
Possible solutions, from most likely to less likely:
- Link to a svd2rust generated device crate
- Check that you actually use the device/hal/bsp crate in your code
- Disable the 'device' feature of cortex-m-rt to build a generic application (a dependency
may be enabling it)
- Supply the interrupt handlers yourself. Check the documentation for details.");

/* ## .text */
ASSERT(ADDR(.vector_table) + SIZEOF(.vector_table) <= _stext, "
ERROR(cortex-m-rt): The .text section can't be placed inside the .vector_table section
Set _stext to an address greater than the end of .vector_table (See output of `nm`)");

ASSERT(_stext + SIZEOF(.text) < ORIGIN(RAM) + LENGTH(RAM), "
ERROR(cortex-m-rt): The .text section must be placed inside the RAM memory.
Set _stext to an address smaller than 'ORIGIN(RAM) + LENGTH(RAM)'");

/* # Other checks */
ASSERT(SIZEOF(.got) == 0, "
ERROR(cortex-m-rt): .got section detected in the input object files
Dynamic relocations are not supported. If you are linking to C code compiled using
the 'cc' crate then modify your build script to compile the C code _without_
the -fPIC flag. See the documentation of the `cc::Build.pic` method for details.");
/* Do not exceed this mark in the error messages above                                    | */


/* Provides weak aliases (cf. PROVIDED) for device specific interrupt handlers */
/* This will usually be provided by a device crate generated using svd2rust (see `device.x`) */
INCLUDE device.x