Collaboration diagram for Startup Support:

Detailed Description

ChibiOS/RT provides its own generic startup file for the ARM Cortex-Mx port. Of course it is not mandatory to use it but care should be taken about the startup phase details.

Startup Process

The startup process, as implemented, is the following:

Interrupts are masked globally.
The two stacks are initialized by assigning them the sizes defined in the linker script (also known as scatter file).
The CPU state is switched to Privileged and the PSP stack is used.
An early initialization routine __early_init() is invoked, if the symbol is not defined then an empty default routine is executed (weak symbol).
DATA and BSS segments are initialized.
Constructors are invoked.
The main() function is invoked with no parameters.
Destructors are invoked.
A branch is performed to the weak symbol _default_exit(). The default code is an endless empty loop.

Expected linker symbols

The startup code starts at the symbol ResetHandler and expects the following symbols to be defined in the linker script:

__ram_end__, end of RAM.
__main_stack_base__, main stack lower boundary.
__main_stack_end__, main stack initial position.
__process_stack_base__, process stack lower boundary.
__process_stack_end__, process stack initial position.
_textdata, address of the data segment source read only data.
_data, start of the data segment.
_edata, end of the data segment end location.
_bss_start, start of the BSS.
_bss_end, end of the BSS segment.
__init_array_start, start of the constructors array.
__init_array_end, end of the constructors array.
__fini_array_start, start of the destructors array.
__fini_array_end, end of the destructors array.

Additionally the kernel expects the following symbols:

__main_thread_stack_base__, this symbol is required when the stack checking is enabled (CH_DBG_ENABLE_STACK_CHECK==TRUE), it is an alias of __process_stack_base__ in this port.
__heap_base__ and __heap_end__, those symbols are required if the memory core manager is enabled (CH_USE_MEMCORE==TRUE) with a default core size set to zero (CH_MEMCORE_SIZE==0).

Functions
void	main (void)
	Application `main()` function.
void	__early_init (void)
	Early initialization.
void	__late_init (void)
	Late initialization.
void	_default_exit (void)
	Default `main()` function exit handler.
void	ResetHandler (void)
	Reset vector.
Startup settings
#define	CRT0_CONTROL_INIT 0x00000002
	Control special register initialization value.
#define	CRT0_STACKS_FILL_PATTERN 0x55555555
	Stack segments initialization switch.
#define	CRT0_INIT_STACKS TRUE
	Stack segments initialization switch.
#define	CRT0_INIT_DATA TRUE
	DATA segment initialization switch.
#define	CRT0_INIT_BSS TRUE
	BSS segment initialization switch.
#define	CRT0_CALL_CONSTRUCTORS TRUE
	Constructors invocation switch.
#define	CRT0_CALL_DESTRUCTORS TRUE
	Destructors invocation switch.
Symbols from the scatter file
uint32_t	__main_stack_base__
	Main stack lower boundary.
uint32_t	__main_stack_end__
	Main stack initial position.
uint32_t	__process_stack_base__
	Process stack lower boundary.
uint32_t	__process_stack_end__
	Process stack initial position.
uint32_t	_textdata
	ROM image of the data segment start.
uint32_t	_data
	Data segment start.
uint32_t	_edata
	Data segment end.
uint32_t	_bss_start
	BSS segment start.
uint32_t	_bss_end
	BSS segment end.
funcp_t	__init_array_start
	Constructors table start.
funcp_t	__init_array_end
	Constructors table end.
funcp_t	__fini_array_start
	Destructors table start.
funcp_t	__fini_array_end
	Destructors table end.

Function Documentation

void main ( void )

Application main() function.

Referenced by ResetHandler().

void __early_init ( void )

Early initialization.

This hook is invoked immediately after the stack initialization and before the DATA and BSS segments initialization. The default behavior is to do nothing.

Note:: This function is a weak symbol.

Definition at line 234 of file crt0.c.

Referenced by ResetHandler().

void __late_init ( void )

Late initialization.

This hook is invoked after the DATA and BSS segments initialization and before any static constructor. The default behavior is to do nothing.

Note:: This function is a weak symbol.

Definition at line 246 of file crt0.c.

Referenced by ResetHandler().

void _default_exit ( void )

Default main() function exit handler.

This handler is invoked or the main() function exit. The default behavior is to enter an infinite loop.

Note:: This function is a weak symbol.

Definition at line 257 of file crt0.c.

Referenced by ResetHandler().

void ResetHandler ( void )

Reset vector.

Definition at line 268 of file crt0.c.

References __early_init(), __fini_array_end, __fini_array_start, __init_array_end, __init_array_start, __late_init(), __main_stack_base__, __main_stack_end__, __process_stack_base__, __process_stack_end__, _bss_end, _bss_start, _data, _default_exit(), _edata, _textdata, CRT0_CONTROL_INIT, CRT0_STACKS_FILL_PATTERN, and main().

Here is the call graph for this function:

Variable Documentation

uint32_t __main_stack_base__

Main stack lower boundary.

This symbol must be exported by the linker script and represents the main stack lower boundary.

Referenced by ResetHandler().

uint32_t __main_stack_end__

Main stack initial position.

This symbol must be exported by the linker script and represents the main stack initial position.

Referenced by ResetHandler().

uint32_t __process_stack_base__

Process stack lower boundary.

This symbol must be exported by the linker script and represents the process stack lower boundary.

Referenced by ResetHandler().

uint32_t __process_stack_end__

Process stack initial position.

This symbol must be exported by the linker script and represents the process stack initial position.

Referenced by ResetHandler().

uint32_t _textdata

ROM image of the data segment start.

Precondition:: The symbol must be aligned to a 32 bits boundary.

Referenced by ResetHandler().

uint32_t _data

Data segment start.

Precondition:: The symbol must be aligned to a 32 bits boundary.

Referenced by ResetHandler().

uint32_t _edata

Data segment end.

Precondition:: The symbol must be aligned to a 32 bits boundary.

Referenced by ResetHandler().

uint32_t _bss_start

BSS segment start.

Precondition:: The symbol must be aligned to a 32 bits boundary.

Referenced by ResetHandler().

uint32_t _bss_end

BSS segment end.

Precondition:: The symbol must be aligned to a 32 bits boundary.

Referenced by ResetHandler().

funcp_t __init_array_start

Constructors table start.

Precondition:: The symbol must be aligned to a 32 bits boundary.

Referenced by ResetHandler().

funcp_t __init_array_end

Constructors table end.

Precondition:: The symbol must be aligned to a 32 bits boundary.

Referenced by ResetHandler().

funcp_t __fini_array_start

Destructors table start.

Precondition:: The symbol must be aligned to a 32 bits boundary.

Referenced by ResetHandler().

funcp_t __fini_array_end

Destructors table end.

Precondition:: The symbol must be aligned to a 32 bits boundary.

Referenced by ResetHandler().

Define Documentation

#define CRT0_CONTROL_INIT 0x00000002

Control special register initialization value.

The system is setup to run in privileged mode using the PSP stack (dual stack mode).

Definition at line 81 of file crt0.c.

Referenced by ResetHandler().

#define CRT0_STACKS_FILL_PATTERN 0x55555555

Stack segments initialization switch.

Definition at line 88 of file crt0.c.

Referenced by ResetHandler().

#define CRT0_INIT_STACKS TRUE

Stack segments initialization switch.

Definition at line 95 of file crt0.c.

#define CRT0_INIT_DATA TRUE

DATA segment initialization switch.

Definition at line 102 of file crt0.c.

#define CRT0_INIT_BSS TRUE

BSS segment initialization switch.

Definition at line 109 of file crt0.c.

#define CRT0_CALL_CONSTRUCTORS TRUE

Constructors invocation switch.

Definition at line 116 of file crt0.c.

#define CRT0_CALL_DESTRUCTORS TRUE

Destructors invocation switch.

Definition at line 123 of file crt0.c.

Detailed Description

Startup Process

Expected linker symbols

Functions

Startup settings

Symbols from the scatter file

Function Documentation

Variable Documentation

Define Documentation