Retro68/libretro/start.c

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/*
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Copyright 2012 Wolfgang Thaller.
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This file is part of Retro68.
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Retro68 is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
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Retro68 is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
along with Retro68. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdint.h>
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#include <Processes.h>
#include <Sound.h>
#include <Memory.h>
#include <OSUtils.h>
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int main(int argc, char* argv[]);
struct flat_hdr {
char magic[4];
unsigned long rev; /* version */
unsigned long entry; /* Offset of first executable instruction
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with text segment from beginning of file */
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unsigned long data_start; /* Offset of data segment from beginning of
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file */
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unsigned long data_end; /* Offset of end of data segment
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from beginning of file */
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unsigned long bss_end; /* Offset of end of bss segment from beginning
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of file */
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/* (It is assumed that data_end through bss_end forms the bss segment.) */
unsigned long stack_size; /* Size of stack, in bytes */
unsigned long reloc_start; /* Offset of relocation records from
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beginning of file */
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unsigned long reloc_count; /* Number of relocation records */
unsigned long flags;
unsigned long filler[6]; /* Reserved, set to zero */
};
typedef void (*voidFunction)(void);
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extern void __init_section(void);
extern void __init_section_end(void);
extern void __fini_section(void);
extern void __fini_section_end(void);
void _start()
{
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long virtualstart, realstart;
__asm__( "move.l #_start, %0" : "=r"(virtualstart) );
__asm__( "lea (_start:w,%%pc), %0" : "=a"(realstart) );
long displacement = realstart - virtualstart;
struct flat_hdr *header = (struct flat_hdr*) (displacement - 0x40);
SysEnvRec env;
long bss_size;
env.processor = 0;
SysEnvirons(0, &env);
bss_size = header->bss_end - header->data_end;
Ptr bss = NewPtrClear(bss_size);
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long n = header->reloc_count;
long *relocs = (long*)( (char*)header + header->reloc_start );
long i;
long data_end = header->data_end - 0x40;
long bss_displacement = (long)bss - data_end;
for(i = 0; i < n; i++)
{
uint8_t *addrPtr = (uint8_t*)(relocs[i] + displacement);
long addr;
addr = (addrPtr[0] << 24) | (addrPtr[1] << 16) | (addrPtr[2] << 8) | addrPtr[3];
addr += addr >= data_end ? bss_displacement : displacement;
addrPtr[0] = addr >> 24;
addrPtr[1] = addr >> 16;
addrPtr[2] = addr >> 8;
addrPtr[3] = addr;
}
if(env.processor >= env68040)
{
FlushCodeCache();
}
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{
char *p = (char*)&__init_section;
char *e = (char*)&__init_section_end;
p += 2;
while( p < e )
{
(*(voidFunction)(*(long*)p))();
p += 6;
}
}
{
char *argv[2] = { "./a.out", NULL };
main(1, argv);
}
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ExitToShell();
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}