/
userland_generic.ld
201 lines (186 loc) · 6.76 KB
/
userland_generic.ld
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/* Userland Generic Layout
*
* This linker script is designed for Tock apps where the end microcontroller
* is not known. Therefore, this script over provisions space on some platforms.
*/
/* Memory Spaces Definitions, 448K flash, 64K ram */
PROG_LENGTH = 0x00070000;
RAM_LENGTH = 0x00010000;
ENTRY(_start)
/* Note: On platforms where apps are position-independent and relocatable, the
* FLASH address here acts as a sentinel value for relocation fixup routines.
* The application loader will select the actual location in flash where the app
* is placed. On platforms where apps are compiled for fixed addresses, these
* addresses will be changed automatically before the linking step.
*/
MEMORY {
FLASH (rx) : ORIGIN = 0x80000000, LENGTH = PROG_LENGTH
SRAM (RWX) : ORIGIN = 0x00000000, LENGTH = RAM_LENGTH
}
SECTIONS {
/* Section for just the app crt0 header.
* This must be first so that the app can find it.
*/
.crt0_header :
{
/**
* Populate the header expected by `crt0`:
*
* struct hdr {
* uint32_t got_sym_start;
* uint32_t got_start;
* uint32_t got_size;
* uint32_t data_sym_start;
* uint32_t data_start;
* uint32_t data_size;
* uint32_t bss_start;
* uint32_t bss_size;
* uint32_t reldata_start;
* uint32_t stack_size;
* };
*/
/* Offset of GOT symbols in flash from the start of the application
* binary. */
LONG(LOADADDR(.got) - ORIGIN(FLASH));
/* Offset of where the GOT section will be placed in memory from the
* beginning of the app's assigned memory. */
LONG(_got - ORIGIN(SRAM));
/* Size of GOT section. */
LONG(SIZEOF(.got));
/* Offset of data symbols in flash from the start of the application
* binary. */
LONG(LOADADDR(.data) - ORIGIN(FLASH));
/* Offset of where the data section will be placed in memory from the
* beginning of the app's assigned memory. */
LONG(_data - ORIGIN(SRAM));
/* Size of data section. */
LONG(SIZEOF(.data));
/* Offset of where the BSS section will be placed in memory from the
* beginning of the app's assigned memory. */
LONG(_bss - ORIGIN(SRAM));
/* Size of BSS section */
LONG(SIZEOF(.bss));
/* First address offset after program flash, where elf2tab places
* .rel.data section */
LONG(LOADADDR(.endflash) - ORIGIN(FLASH));
/* The size of the stack requested by this application */
LONG(STACK_SIZE);
} > FLASH =0xFF
/* App state section. Used for persistent app data.
* We put this first so that if the app code changes but the persistent
* data doesn't, the app_state can be preserved.
*/
.wfr.app_state :
{
KEEP (*(.app_state))
. = ALIGN(4); /* Make sure we're word-aligned here */
} > FLASH =0xFF
/* Text section, Code! */
.text :
{
. = ALIGN(4);
_text = .;
KEEP (*(.start))
*(.text*)
*(.rodata*)
*(.srodata*) /* for RISC-V */
KEEP (*(.syscalls))
_etext = .;
*(.ARM.extab*)
. = ALIGN(4); /* Make sure we're word-aligned here */
} > FLASH =0xFF
/* Need to reserve room for the stack in the linker file. This makes the
* _got addresses used by the compiler match what they will be when the
* app is loaded into memory. This is not necessary for full PIC supported
* platforms (like Cortex-M), but is needed when an app is compiled for a
* fixed address.
*/
.stack :
{
/* elf2tab requires that the `_SRAM_ORIGIN` symbol be present to
* mark the first address in the SRAM memory. Since ELF files do
* not really need to specify this address as they only care about
* loading into flash, we need to manually mark this address for
* elf2tab. elf2tab will use it to add a fixed address header in the
* TBF header if needed.
*/
_sram_origin = .;
/* Be conservative about our alignment for the stack. Different
* architectures require different values (8 for ARM, 16 for RISC-V),
* so we choose the largest value. In practice, this likely will not
* matter since the start of SRAM is unlikely to be at a very peculiar
* address.
*/
. = ALIGN(16);
_stack = .;
. = _stack + STACK_SIZE;
. = ALIGN(16);
} > SRAM
/* Global Offset Table */
.got :
{
. = ALIGN(4); /* Make sure we're word-aligned here */
_got = .;
*(.got*)
*(.got.plt*)
. = ALIGN(4);
} > SRAM AT > FLASH
/* Data section, static initialized variables
* Note: This is placed in Flash after the text section, but needs to be
* moved to SRAM at runtime
*/
.data :
{
. = ALIGN(4); /* Make sure we're word-aligned here */
_data = .;
KEEP(*(.data*))
/* Include the "small data" in the data section. Otherwise it will be
* dropped when the TBF is created.
*/
KEEP(*(.sdata*))
. = ALIGN(4); /* Make sure we're word-aligned at the end of flash */
} > SRAM AT > FLASH
/* BSS section, static uninitialized variables */
.bss :
{
. = ALIGN(4); /* Make sure we're word-aligned here */
_bss = .;
KEEP(*(.bss*))
KEEP(*(.sbss*)) /* for RISC-V */
*(COMMON)
. = ALIGN(4);
} > SRAM
/* End of flash. */
.endflash :
{
} > FLASH
/* ARM Exception support
*
* This contains compiler-generated support for unwinding the stack,
* consisting of key-value pairs of function addresses and information on
* how to unwind stack frames.
* https://wiki-archive.linaro.org/KenWerner/Sandbox/libunwind
* (See also https://github.com/tock/libtock-c/issues/48)
*
*
* .ARM.exidx is sorted, so has to go in its own output section.
*
* __NOTE__: It's at the end because we currently don't actually serialize
* it to the binary in elf2tab. If it was before the RAM sections, it would
* through off our calculations of the header.
*
* The section is marked as NOLOAD, to ensure elf2tab does not serialize it
* https://github.com/tock/elf2tab/pull/66
*/
PROVIDE_HIDDEN (__exidx_start = .);
.ARM.exidx (NOLOAD) :
{
/* (C++) Index entries for section unwinding */
*(.ARM.exidx* .gnu.linkonce.armexidx.*)
} > FLASH
PROVIDE_HIDDEN (__exidx_end = .);
}
ASSERT(_got <= _bss, "
The GOT section must be before the BSS section for crt0 setup to be correct.");
ASSERT(_data <= _bss, "
The data section must be before the BSS section for crt0 setup to be correct.");