boot-d45.c
/** \file
* Startup code for DIGIC 4 and 5
* ("Classic" boot process)
*/
#include "dryos.h"
#include "boot.h"
/** These are called when new tasks are created */
static int my_init_task(int a, int b, int c, int d);
/** This just goes into the bss */
#define RELOCSIZE 0x3000 // look in HIJACK macros for the highest address, and subtract ROMBASEADDR
static uint32_t _reloc[ RELOCSIZE / 4 ];
#define RELOCADDR ((uintptr_t) _reloc)
/** Translate a firmware address into a relocated address */
#define INSTR( addr ) ( *(uint32_t*)( (addr) - ROMBASEADDR + RELOCADDR ) )
/** Fix a branch instruction in the relocated firmware image */
#define FIXUP_BRANCH( rom_addr, dest_addr ) \
INSTR( rom_addr ) = BL_INSTR( &INSTR( rom_addr ), (dest_addr) )
void
__attribute__((noreturn,noinline,naked))
copy_and_restart( int offset )
{
zero_bss();
// Copy the firmware to somewhere safe in memory
const uint8_t * const firmware_start = (void*) ROMBASEADDR;
const uint32_t firmware_len = RELOCSIZE;
uint32_t * const new_image = (void*) RELOCADDR;
blob_memcpy( new_image, firmware_start, firmware_start + firmware_len );
/*
* in cstart() (0xff010ff4) make these changes:
* calls bzero(), then loads bs_end and calls
* create_init_task
*/
// Reserve memory after the BSS for our application
// This is done by resizing the malloc memory pool (user_mem_start in DryOS memory map),
// We are going to change its start address, to begin right after our BSS,
// (which is the last segment in our binary - see magiclantern.lds.S). */
// Malloc memory is usually specified by its start and end address.
// Exception: DIGIC 6 uses start address + size.
// Cannot use qprintf here (no snprintf).
qprint("[BOOT] changing user_mem_start from "); qprintn(INSTR(HIJACK_INSTR_BSS_END));
qprint("to "); qprintn((uintptr_t)_bss_end); qprint("\n");
INSTR( HIJACK_INSTR_BSS_END ) = (uintptr_t) _bss_end;
ml_reserved_mem = (uintptr_t)_bss_end - RESTARTSTART;
// Fix the calls to bzero32() and create_init_task()
FIXUP_BRANCH( HIJACK_FIXBR_BZERO32, bzero32 );
FIXUP_BRANCH( HIJACK_FIXBR_CREATE_ITASK, create_init_task );
// Set our init task to run instead of the firmware one
qprint("[BOOT] changing init_task from "); qprintn(INSTR( HIJACK_INSTR_MY_ITASK ));
qprint("to "); qprintn((uint32_t) my_init_task); qprint("\n");
INSTR( HIJACK_INSTR_MY_ITASK ) = (uint32_t) my_init_task;
// Make sure that our self-modifying code clears the cache
sync_caches();
// We enter after the signature, avoiding the
// relocation jump that is at the head of the data
thunk reloc_entry = (thunk)( RELOCADDR + 0xC );
reloc_entry();
// Unreachable
while(1)
;
}