rt0.cpp
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extern "C" {
#include "rt0.h"
}
#include <stdint.h>
#include <string.h>
#include <ion.h>
#include "../device.h"
#include "../console.h"
typedef void (*cxx_constructor)();
extern "C" {
extern char _data_section_start_flash;
extern char _data_section_start_ram;
extern char _data_section_end_ram;
extern char _bss_section_start_ram;
extern char _bss_section_end_ram;
extern cxx_constructor _init_array_start;
extern cxx_constructor _init_array_end;
}
void abort() {
#if DEBUG
while (1) {
}
#else
Ion::reset();
#endif
}
void start() {
// This is where execution starts after reset.
// Many things are not initialized yet so the code here has to pay attention.
/* Copy data section to RAM
* The data section is R/W but its initialization value matters. It's stored
* in Flash, but linked as if it were in RAM. Now's our opportunity to copy
* it. Note that until then the data section (e.g. global variables) contains
* garbage values and should not be used. */
size_t dataSectionLength = (&_data_section_end_ram - &_data_section_start_ram);
memcpy(&_data_section_start_ram, &_data_section_start_flash, dataSectionLength);
/* Zero-out the bss section in RAM
* Until we do, any uninitialized global variable will be unusable. */
size_t bssSectionLength = (&_bss_section_end_ram - &_bss_section_start_ram);
memset(&_bss_section_start_ram, 0, bssSectionLength);
/* Initialize the FPU as early as possible.
* For example, static C++ objects are very likely to manipulate float values */
Ion::Device::initFPU();
/* Call static C++ object constructors
* The C++ compiler creates an initialization function for each static object.
* The linker then stores the address of each of those functions consecutively
* between _init_array_start and _init_array_end. So to initialize all C++
* static objects we just have to iterate between theses two addresses and
* call the pointed function. */
for (cxx_constructor * c = &_init_array_start; c<&_init_array_end; c++) {
(*c)();
}
Ion::Device::init();
ion_app();
abort();
}