328 lines
9.7 KiB
C
328 lines
9.7 KiB
C
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//
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// This file is part of the µOS++ III distribution.
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// Copyright (c) 2014 Liviu Ionescu.
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//
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// ----------------------------------------------------------------------------
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// This module contains the startup code for a portable embedded
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// C/C++ application, built with newlib.
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//
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// Control reaches here from the reset handler via jump or call.
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//
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// The actual steps performed by _start are:
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// - copy the initialised data region(s)
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// - clear the BSS region(s)
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// - initialise the system
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// - run the preinit/init array (for the C++ static constructors)
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// - initialise the arc/argv
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// - branch to main()
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// - run the fini array (for the C++ static destructors)
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// - call _exit(), directly or via exit()
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//
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// If OS_INCLUDE_STARTUP_INIT_MULTIPLE_RAM_SECTIONS is defined, the
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// code is capable of initialising multiple regions.
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//
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// The normal configuration is standalone, with all support
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// functions implemented locally.
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//
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// For this to be called, the project linker must be configured without
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// the startup sequence (-nostartfiles).
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// ----------------------------------------------------------------------------
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#include <stdint.h>
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#include <sys/types.h>
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// ----------------------------------------------------------------------------
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#if !defined(OS_INCLUDE_STARTUP_GUARD_CHECKS)
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#define OS_INCLUDE_STARTUP_GUARD_CHECKS (1)
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#endif
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// ----------------------------------------------------------------------------
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#if !defined(OS_INCLUDE_STARTUP_INIT_MULTIPLE_RAM_SECTIONS)
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// Begin address for the initialisation values of the .data section.
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// defined in linker script
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extern unsigned int _sidata;
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// Begin address for the .data section; defined in linker script
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extern unsigned int _sdata;
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// End address for the .data section; defined in linker script
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extern unsigned int _edata;
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// Begin address for the .bss section; defined in linker script
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extern unsigned int __bss_start__;
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// End address for the .bss section; defined in linker script
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extern unsigned int __bss_end__;
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#else
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// The following symbols are constructs generated by the linker, indicating
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// the location of various points in the "Memory regions initialisation arrays".
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// These arrays are created by the linker via the managed linker script
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// of each RW data mechanism. It contains the load address, execution address
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// and length section and the execution and length of each BSS (zero
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// initialised) section.
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extern unsigned int __data_regions_array_start;
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extern unsigned int __data_regions_array_end;
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extern unsigned int __bss_regions_array_start;
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extern unsigned int __bss_regions_array_end;
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#endif
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extern void
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__initialize_args (int*, char***);
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// main() is the entry point for newlib based applications.
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// By default, there are no arguments, but this can be customised
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// by redefining __initialize_args(), which is done when the
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// semihosting configurations are used.
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extern int
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start_application (int argc, char* argv[]);
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// The implementation for the exit routine; for embedded
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// applications, a system reset will be performed.
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extern void
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__attribute__((noreturn))
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_exit (int);
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// ----------------------------------------------------------------------------
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// Forward declarations
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void
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_start (void);
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void
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__initialize_data (unsigned int* from, unsigned int* region_begin,
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unsigned int* region_end);
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void
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__initialize_bss (unsigned int* region_begin, unsigned int* region_end);
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void
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__run_init_array (void);
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void
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__run_fini_array (void);
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void
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__initialize_hardware_early (void);
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void
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__initialize_hardware (void);
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// ----------------------------------------------------------------------------
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inline void
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__attribute__((always_inline))
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__initialize_data (unsigned int* from, unsigned int* region_begin,
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unsigned int* region_end)
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{
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// Iterate and copy word by word.
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// It is assumed that the pointers are word aligned.
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unsigned int *p = region_begin;
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while (p < region_end)
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*p++ = *from++;
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}
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inline void
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__attribute__((always_inline))
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__initialize_bss (unsigned int* region_begin, unsigned int* region_end)
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{
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// Iterate and clear word by word.
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// It is assumed that the pointers are word aligned.
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unsigned int *p = region_begin;
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while (p < region_end)
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*p++ = 0;
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}
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// These magic symbols are provided by the linker.
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extern void
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(*__preinit_array_start[]) (void) __attribute__((weak));
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extern void
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(*__preinit_array_end[]) (void) __attribute__((weak));
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extern void
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(*__init_array_start[]) (void) __attribute__((weak));
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extern void
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(*__init_array_end[]) (void) __attribute__((weak));
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extern void
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(*__fini_array_start[]) (void) __attribute__((weak));
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extern void
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(*__fini_array_end[]) (void) __attribute__((weak));
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// Iterate over all the preinit/init routines (mainly static constructors).
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inline void
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__attribute__((always_inline))
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__run_init_array (void)
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{
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int count;
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int i;
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count = __preinit_array_end - __preinit_array_start;
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for (i = 0; i < count; i++)
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__preinit_array_start[i] ();
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// If you need to run the code in the .init section, please use
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// the startup files, since this requires the code in crti.o and crtn.o
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// to add the function prologue/epilogue.
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//_init(); // DO NOT ENABE THIS!
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count = __init_array_end - __init_array_start;
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for (i = 0; i < count; i++)
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__init_array_start[i] ();
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}
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// Run all the cleanup routines (mainly static destructors).
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inline void
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__attribute__((always_inline))
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__run_fini_array (void)
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{
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int count;
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int i;
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count = __fini_array_end - __fini_array_start;
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for (i = count; i > 0; i--)
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__fini_array_start[i - 1] ();
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// If you need to run the code in the .fini section, please use
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// the startup files, since this requires the code in crti.o and crtn.o
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// to add the function prologue/epilogue.
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//_fini(); // DO NOT ENABE THIS!
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}
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#if defined(DEBUG) && (OS_INCLUDE_STARTUP_GUARD_CHECKS)
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// These definitions are used to check if the routines used to
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// clear the BSS and to copy the initialised DATA perform correctly.
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#define BSS_GUARD_BAD_VALUE (0xCADEBABA)
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static uint32_t volatile __attribute__ ((section(".bss_begin")))
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__bss_begin_guard;
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static uint32_t volatile __attribute__ ((section(".bss_end")))
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__bss_end_guard;
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#define DATA_GUARD_BAD_VALUE (0xCADEBABA)
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#define DATA_BEGIN_GUARD_VALUE (0x12345678)
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#define DATA_END_GUARD_VALUE (0x98765432)
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static uint32_t volatile __attribute__ ((section(".data_begin")))
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__data_begin_guard = DATA_BEGIN_GUARD_VALUE;
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static uint32_t volatile __attribute__ ((section(".data_end")))
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__data_end_guard = DATA_END_GUARD_VALUE;
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#endif // defined(DEBUG) && (OS_INCLUDE_STARTUP_GUARD_CHECKS)
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// This is the place where Cortex-M core will go immediately after reset,
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// via a call or jump from the Reset_Handler.
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//
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// For the call to work, and for the call to __initialize_hardware_early()
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// to work, the reset stack must point to a valid internal RAM area.
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void __attribute__ ((section(".after_vectors"),noreturn,weak))
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_start (void)
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{
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// Initialise hardware right after reset, to switch clock to higher
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// frequency and have the rest of the initialisations run faster.
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//
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// Mandatory on platforms like Kinetis, which start with the watch dog
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// enabled and require an early sequence to disable it.
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//
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// Also useful on platform with external RAM, that need to be
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// initialised before filling the BSS section.
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__initialize_hardware_early ();
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// Use Old Style DATA and BSS section initialisation,
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// that will manage a single BSS sections.
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#if defined(DEBUG) && (OS_INCLUDE_STARTUP_GUARD_CHECKS)
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__data_begin_guard = DATA_GUARD_BAD_VALUE;
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__data_end_guard = DATA_GUARD_BAD_VALUE;
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#endif
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#if !defined(OS_INCLUDE_STARTUP_INIT_MULTIPLE_RAM_SECTIONS)
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// Copy the DATA segment from Flash to RAM (inlined).
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__initialize_data(&_sidata, &_sdata, &_edata);
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#else
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// Copy the data sections from flash to SRAM.
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for (unsigned int* p = &__data_regions_array_start;
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p < &__data_regions_array_end;)
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{
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unsigned int* from = (unsigned int *) (*p++);
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unsigned int* region_begin = (unsigned int *) (*p++);
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unsigned int* region_end = (unsigned int *) (*p++);
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__initialize_data (from, region_begin, region_end);
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}
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#endif
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#if defined(DEBUG) && (OS_INCLUDE_STARTUP_GUARD_CHECKS)
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if ((__data_begin_guard != DATA_BEGIN_GUARD_VALUE)
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|| (__data_end_guard != DATA_END_GUARD_VALUE))
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{
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for (;;)
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;
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}
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#endif
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#if defined(DEBUG) && (OS_INCLUDE_STARTUP_GUARD_CHECKS)
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__bss_begin_guard = BSS_GUARD_BAD_VALUE;
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__bss_end_guard = BSS_GUARD_BAD_VALUE;
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#endif
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#if !defined(OS_INCLUDE_STARTUP_INIT_MULTIPLE_RAM_SECTIONS)
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// Zero fill the BSS section (inlined).
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__initialize_bss(&__bss_start__, &__bss_end__);
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#else
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// Zero fill all bss segments
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for (unsigned int *p = &__bss_regions_array_start;
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p < &__bss_regions_array_end;)
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{
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unsigned int* region_begin = (unsigned int*) (*p++);
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unsigned int* region_end = (unsigned int*) (*p++);
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__initialize_bss (region_begin, region_end);
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}
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#endif
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#if defined(DEBUG) && (OS_INCLUDE_STARTUP_GUARD_CHECKS)
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if ((__bss_begin_guard != 0) || (__bss_end_guard != 0))
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{
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for (;;)
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;
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}
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#endif
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// Hook to continue the initialisations. Usually compute and store the
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// clock frequency in the global CMSIS variable, cleared above.
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__initialize_hardware ();
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// Get the argc/argv (useful in semihosting configurations).
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int argc;
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char** argv;
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__initialize_args (&argc, &argv);
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// Call the standard library initialisation (mandatory for C++ to
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// execute the constructors for the static objects).
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__run_init_array ();
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// Call the main entry point, and save the exit code.
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int code = start_application (argc, argv);
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// Run the C++ static destructors.
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__run_fini_array ();
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_exit (code);
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// Should never reach this, _exit() should have already
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// performed a reset.
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for (;;)
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;
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}
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// ----------------------------------------------------------------------------
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