Retro68/libretro/relocate.c
2015-08-29 20:11:53 +02:00

248 lines
6.6 KiB
C

/*
Copyright 2015 Wolfgang Thaller.
This file is part of Retro68.
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.
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.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>.
*/
#include <stdint.h>
#include <stdlib.h>
#include <Processes.h>
#include <Sound.h>
#include <Memory.h>
#include <OSUtils.h>
#include "Retro68Runtime.h"
struct flat_hdr {
char magic[4];
unsigned long rev; /* version */
unsigned long entry; /* Offset of first executable instruction
with text segment from beginning of file */
unsigned long data_start; /* Offset of data segment from beginning of
file */
unsigned long data_end; /* Offset of end of data segment
from beginning of file */
unsigned long bss_end; /* Offset of end of bss segment from beginning
of file */
/* (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
beginning of file */
unsigned long reloc_count; /* Number of relocation records */
unsigned long flags;
unsigned long filler[6]; /* Reserved, set to zero */
};
typedef void (*voidFunction)(void);
extern void __init_section(void);
extern void __init_section_end(void);
extern void __fini_section(void);
extern void __fini_section_end(void);
typedef struct Retro68RelocState
{
long headerVirtualAddress;
Ptr bssPtr;
Handle codeHandle;
} Retro68RelocState;
static Retro68RelocState relocState __attribute__ ((nocommon)) = {
-sizeof(struct flat_hdr), NULL, NULL
};
#if 1
#define assert(x) do { } while(0)
#else
#define assert(x) do { \
if(!(x)) {\
unsigned char str[6]; \
int i; \
int l = __LINE__; \
for(i = 1; i < 6; i++) \
str[i] = ' '; \
str[0] = 5; \
str[5] = '0'; \
for(i = 5; l && i > 0; i--) \
{ \
str[i] = '0' + (l % 10); \
l /= 10; \
} \
DebugStr(str); \
} \
} while(0)
#endif
void Retro68Relocate()
{
// Figure out the displacement
// what is the difference between the addresses in our program code
// and an address calculated by PC-relative access?
long displacement;
RETRO68_GET_DISPLACEMENT_STRIP(displacement);
struct Retro68RelocState *rState = (Retro68RelocState*)
((char*)&relocState + displacement);
// rState now points to the global relocState variable
if(displacement == 0)
{
if(rState->bssPtr)
{
// this is not the first time, no relocations needed.
// should only happen for code resources
// that are invoked more than once.
// Lock the code to be sure.
HLock(rState->codeHandle);
return;
}
}
// Locate the start of the FLT file header inside the code resource
long headerOldVirtualAddress = rState->headerVirtualAddress;
struct flat_hdr *header = (struct flat_hdr*) (headerOldVirtualAddress + displacement);
uint8_t *base = (uint8_t*) (header+1);
// Recover the handle to the code resource by looking at the
// longword before the FLT header. The resource templates in Retro68.r store the offset
// from the beginning of the code resource there.
uint32_t headerOffsetInResource = ((uint32_t*)header)[-1];
if(headerOffsetInResource < 4096)
// Arbitrary magic number. We expect the offset to be small, just a few header bytes before it.
// if it's out of range, assume the longword before the header is not the offset we're looking for.
{
Handle h = RecoverHandle((Ptr) header - headerOffsetInResource);
if(MemError() == noErr && h)
{
// Make sure the code is locked. Only relevant for some code resources.
HLock(h);
rState->codeHandle = h;
}
}
long bss_size = header->bss_end - header->data_end;
long n = header->reloc_count;
long *relocs = (long*)( (char*)header + header->reloc_start );
long i;
long data_end = header->data_end + headerOldVirtualAddress;
uint32_t flt_size = (uint32_t) header->data_end;
long bss_displacement = 0;
// Allocate BSS section (uninitialized/zero-initialized global data)
if(!rState->bssPtr)
{
THz zone = ApplicationZone();
if(!zone || (char*)header < (char*)zone)
rState->bssPtr = NewPtrSysClear(bss_size);
else
rState->bssPtr = NewPtrClear(bss_size);
bss_displacement = (long)(rState->bssPtr) - data_end;
}
// Process relocation records
for(i = 0; i < n; i++)
{
uint8_t *addrPtr = base + relocs[i];
uint32_t addr;
assert((Ptr)addrPtr >= (Ptr)header);
assert((Ptr)addrPtr < (Ptr)header + flt_size);
//addr = *(uint32_t*)addrPtr;
addr = (((((addrPtr[0] << 8) | addrPtr[1]) << 8) | addrPtr[2]) << 8) | addrPtr[3];
assert(addr + 0x40 >= headerOldVirtualAddress + 0x40);
assert(addr + 0x40 < headerOldVirtualAddress + header->bss_end + 0x40);
addr += (uint32_t)(addr - headerOldVirtualAddress) >= flt_size ?
bss_displacement : displacement;
assert((Ptr)addr >= (Ptr)header && (Ptr)addr < (Ptr)header + flt_size
|| (Ptr)addr >= rState->bssPtr && (Ptr)addr < rState->bssPtr + bss_size);
addrPtr[3] = addr;
addrPtr[2] = (addr >>= 8);
addrPtr[1] = (addr >>= 8);
addrPtr[0] = (addr >>= 8);
//*(uint32_t*)addrPtr = addr;
}
// We're basically done.
// Now check whether we're on 68040 or later and need to flush the cache.
SysEnvRec env;
env.processor = 0;
SysEnvirons(0, &env);
if(env.processor >= env68040)
{
FlushCodeCache();
}
// accessing globals and calling functions is OK below here.
rState->headerVirtualAddress += displacement;
}
void Retro68CallConstructors()
{
char *p = (char*)&__init_section;
char *e = (char*)&__init_section_end;
p += 2;
while( p < e )
{
(*(voidFunction)(*(long*)p))();
p += 6;
}
}
void Retro68CallDestructors()
{
char *p = (char*)&__fini_section;
char *e = (char*)&__fini_section_end;
p += 2;
while( p < e )
{
(*(voidFunction)(*(long*)p))();
p += 6;
}
}
void Retro68FreeGlobals()
{
if(relocState.bssPtr != (Ptr) -1)
{
DisposePtr(relocState.bssPtr);
relocState.bssPtr = (Ptr) -1;
}
}