Macintosh-Tools/Retro68
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Support for older systems (64K ROMs). See issue #22.

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Thanks to @mdanh2002 for submitting the patch.
This commit is contained in:
Wolfgang Thaller 2017-04-11 20:42:12 +02:00
parent 26c2330aae
commit 95b59e3315
2 changed files with 67 additions and 24 deletions
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13
libretro/Retro68Runtime.h
View File

@ -36,6 +36,19 @@
#define RETRO68_GET_DISPLACEMENT(DISPLACEMENT) \
_RETRO68_GET_DISPLACEMENT(DISPLACEMENT, )
// Calls to the StripAddress() trap are supposed to make sure addresses are 32-bit clean.
// But this trap doesn’t exist on old ROMs and old system versions,
// so programs built with StripAddress will mysteriously crash.
// Those systems always run in 24-bit mode, so we can just take the lower 24
// bits of the 32 bit address.
// StripAddress24 must not be used on 32-bit systems, or the resulting crashes
// will be even more mysterious.
#define StripAddress24(x) ((char*) ((unsigned long)(x) & 0x00FFFFFF))
#define RETRO68_GET_DISPLACEMENT_STRIP24(DISPLACEMENT) \
_RETRO68_GET_DISPLACEMENT(DISPLACEMENT, StripAddress24)
// original StripAddress
#define RETRO68_GET_DISPLACEMENT_STRIP(DISPLACEMENT) \
_RETRO68_GET_DISPLACEMENT(DISPLACEMENT, StripAddress)

40
libretro/relocate.c
View File

@ -30,6 +30,7 @@
#include <Sound.h>
#include <Memory.h>
#include <OSUtils.h>
#include <Traps.h>
#include "Retro68Runtime.h"
@ -98,16 +99,42 @@ static Retro68RelocState relocState __attribute__ ((nocommon)) = {
void Retro68Relocate()
{
// memory address to retrieve the ROM type (64K or a later ROM)
// see for details http://www.mac.linux-m68k.org/devel/macalmanac.php
short* ROM85 = (short*) 0x028E;
// figure out which trap is supported
Boolean is128KROM = ((*ROM85) > 0);
Boolean hasSysEnvirons = false;
Boolean hasStripAddr = false;
if (is128KROM)
{
UniversalProcPtr trapSysEnv = GetOSTrapAddress(_SysEnvirons);
UniversalProcPtr trapStripAddr = GetOSTrapAddress(_StripAddress);
UniversalProcPtr trapUnimpl = GetOSTrapAddress(_Unimplemented);
hasSysEnvirons = (trapSysEnv != trapUnimpl);
hasStripAddr = (trapStripAddr != trapUnimpl);
}
// 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;
if (hasStripAddr)
{
RETRO68_GET_DISPLACEMENT_STRIP(displacement);
}
else
{
RETRO68_GET_DISPLACEMENT_STRIP24(displacement);
}
struct Retro68RelocState *rState = (Retro68RelocState*)
((char*)&relocState + displacement);
// rState now points to the global relocState variable
// rState now points to the global relocState variable
if(displacement == 0)
{
if(rState->bssPtr)
@ -127,7 +154,6 @@ void Retro68Relocate()
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.
@ -146,8 +172,6 @@ void Retro68Relocate()
}
}
long bss_size = header->bss_end - header->data_end;
long n = header->reloc_count;
@ -198,6 +222,11 @@ void Retro68Relocate()
// We're basically done.
// Now check whether we're on 68040 or later and need to flush the cache.
// only do this if SysEnvirons is available.
// if SysEnvirons is not available, that means we're on an old System or ROM
// and likely not using a 68040, so we won't do this
if (hasSysEnvirons)
{
SysEnvRec env;
env.processor = 0;
@ -206,8 +235,9 @@ void Retro68Relocate()
{
FlushCodeCache();
}
// accessing globals and calling functions is OK below here.
}
// accessing globals and calling functions is OK below here.
rState->headerVirtualAddress += displacement;
}