Reorganize startup code (make some parts publicly available)

CMakeLists.txt

@@ -23,6 +23,7 @@ add_subdirectory(libretro)
 
 # add library path so that GCC picks up the freshly-built libretro
 link_directories(${CMAKE_CURRENT_BINARY_DIR}/libretro)
+include_directories(${CMAKE_CURRENT_SOURCE_DIR}/libretro)
 
 add_subdirectory(Console)
 add_subdirectory(TestApps)

libretro/CMakeLists.txt

@@ -23,7 +23,10 @@
 
 cmake_minimum_required(VERSION 2.8)
 
-add_library(retrocrt start.c
+add_library(retrocrt
+	Retro68Runtime.h
+	start.c
+	relocate.c
 	malloc.c
 	syscalls.c
 	glue.c

libretro/Retro68Runtime.h

@@ -0,0 +1,46 @@
+/*
+	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/>.
+*/
+
+#define RETRO68_GET_DISPLACEMENT(DISPLACEMENT) \
+	do {	\
+		long virtualstart, realstart;	\
+		__asm__( "1:\n"	\
+				 "\tmove.l #1b, %0\n"	\
+				 "\tlea (1b:w,%%pc), %1" \
+				: "=r"(virtualstart) , "=a"(realstart) );	\
+		DISPLACEMENT = realstart - virtualstart;	\
+	} while(0)
+
+#define RETRO68_CALL_UNRELOCATED(FUN,ARGS) \
+	do {	\
+		long displacement;	\
+		RETRO68_GET_DISPLACEMENT(displacement);	\
+		(*(typeof(&FUN)) ((char*)(&FUN) + displacement)) ARGS;	\
+	} while(0)
+
+void Retro68Relocate();
+void Retro68CallConstructors();
+
+#define RETRO68_RELOCATE() RETRO68_CALL_UNRELOCATED(Retro68Relocate,())

libretro/relocate.c

@@ -0,0 +1,137 @@
+/*
+	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);
+
+
+
+static long headerVirtualAddress = -0x40;
+static Ptr savedBSS = (Ptr) -1;
+
+#define ACCESS_DISPLACED(VAR) \
+	( * (typeof(&VAR)) ((char*)(&VAR) + displacement) )
+
+void Retro68Relocate()
+{
+	long displacement;
+	RETRO68_GET_DISPLACEMENT(displacement);
+
+	struct flat_hdr *header = (struct flat_hdr*) (ACCESS_DISPLACED(headerVirtualAddress) + displacement);
+
+	SysEnvRec env;
+	long bss_size;
+
+	env.processor = 0;
+	SysEnvirons(0, &env);
+
+	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 - 0x40;
+	long bss_displacement = 0;
+
+	Ptr bss = ACCESS_DISPLACED(savedBSS);
+	if(bss == (Ptr)-1)
+	{
+		bss = NewPtrClear(bss_size);
+		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();
+	}
+	// accessing globals and calling functions is OK below here.
+
+	headerVirtualAddress += displacement;
+	savedBSS = bss;
+}
+
+void Retro68CallConstructors()
+{
+	char *p = (char*)&__init_section;
+	char *e = (char*)&__init_section_end;
+	p += 2;
+	while( p < e )
+	{
+		(*(voidFunction)(*(long*)p))();
+		p += 6;
+	}
+}

libretro/start.c

@@ -25,101 +25,17 @@
 
 #include <stdint.h>
 #include <stdlib.h>
+#include <SegLoad.h>
 
-#include <Processes.h>
+#include "Retro68Runtime.h"
-#include <Sound.h>
-#include <Memory.h>
-#include <OSUtils.h>
-
 
 int main(int argc, char* argv[]);
 
-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);
-
-
 void _start()
 {
-	
+	RETRO68_RELOCATE();
-	long virtualstart, realstart;
+	Retro68CallConstructors();
-	
-	__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);
-
-	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();
-	}
-	{
-		char *p = (char*)&__init_section;
-		char *e = (char*)&__init_section_end;
-		p += 2;
-		while( p < e )
-		{
-			(*(voidFunction)(*(long*)p))();
-			p += 6;
-		}
-	}
-	
 	int result;
 	{
 		char *argv[2] = { "./a.out", NULL };