Merge in __PAGEZERO hack from Michael Z. Sliczniak so that REAL_ADDRESSING

mode can work under Darwin.

BasiliskII/src/Unix/Darwin/lowmem.c

@@ -0,0 +1,148 @@
+/*
+ *  lowmem.c - enable access to low memory globals on Darwin
+ *
+ *  Copyright (c) 2003 Michael Z. Sliczniak
+ *
+ *  Basilisk II (C) 1997-2003 Christian Bauer
+ *
+ *  This program 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 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <mach/vm_prot.h>
+#include <mach-o/loader.h>
+
+static const char progname[] = "lowmem";
+
+/*
+ * Under Mach there is very little assumed about the memory map of object
+ * files. It is the job of the loader to create the initial memory map of an
+ * executable. In a Mach-O executable there will be numerous loader commands
+ * that the loader must process. Some of these will create the initial memory
+ * map used by the executable. Under Darwin the static object file linker,
+ * ld, automatically adds the __PAGEZERO segment to all executables. The
+ * default size of this segment is the page size of the target system and
+ * the initial and maximum permissions are set to allow no access. This is so
+ * that all programs fault on a NULL pointer dereference. Arguably this is
+ * incorrect and the maximum permissions shoould be rwx so that programs can
+ * change this default behavior. Then programs could be written that assume
+ * a null string at the null address, which was the convention on some
+ * systems. In our case we need to have 8K mapped at zero for the low memory
+ * globals and this program modifies the segment load command in the
+ * basiliskII executable so that it can be used for data.
+ */
+
+int
+main(int argc, const char *argv[])
+{
+	int fd;
+	char *addr;
+	struct mach_header *machhead;
+	struct segment_command *sc_cmd;
+
+	if (argc != 2) {
+		(void)fprintf(stderr, "Usage: %s executable\n", progname);
+		exit(1);
+	}
+
+	fd = open(argv[1], O_RDWR, 0);
+	if (fd == -1) {
+		(void)fprintf(stderr, "%s: could not open %s: %s\n",
+			progname, argv[1], strerror(errno));
+		exit(1);
+	}
+
+	/*
+	 * Size does not really matter, it will be rounded-up to a multiple
+	 * of the page size automatically.
+	 */
+	addr = mmap(NULL, 0x1000, PROT_READ | PROT_WRITE,
+	    MAP_FILE | MAP_SHARED, fd, 0);
+	if (addr == NULL) {
+		(void)fprintf(stderr, "%s: could not mmap %s: %s\n",
+				progname, argv[1], strerror(errno));
+		exit(1);
+	}
+
+	/*
+	 * Check to see if the Mach-O magic bytes are in the header.
+	 * If we cared about cross compiling we would also check against
+	 * MH_CIGAM and then change the endianness with every access, but
+	 * we do not care about that.
+	 */
+	machhead = (void *)addr;
+	if (machhead->magic != MH_MAGIC) {
+		(void)fprintf(stderr, "%s: %s does not appear to be a Mach-O object file\n",
+				progname, argv[1]);
+		exit(1);
+	}
+
+	if (machhead->filetype != MH_EXECUTE) {
+		(void)fprintf(stderr, "%s: %s does not appear to be an executable file\n",
+				progname, argv[1]);
+		exit(1);
+	}
+
+	if (machhead->ncmds == 0) {
+		(void)fprintf(stderr, "%s: %s does not contain any load commands\n",
+				progname, argv[1]);
+		exit(1);
+	}
+
+	sc_cmd = (void *)&machhead[1];
+	if (sc_cmd->cmd != LC_SEGMENT){
+		(void)fprintf(stderr, "%s: load segment not first command in %s\n",
+				progname, argv[1]);
+		exit(1);
+	}
+
+	if (strncmp(sc_cmd->segname, "__PAGEZERO",
+			 sizeof (*sc_cmd->segname))) {
+		(void)fprintf(stderr, "%s: zero page not first segment in %s\n",
+				progname, argv[1]);
+		exit(1);
+	}
+
+	/* change the permissions */
+	sc_cmd->maxprot = VM_PROT_ALL;
+	sc_cmd->initprot = VM_PROT_ALL;
+
+	/*
+	 * We do not make __PAGEZERO 8K in this program because then
+	 * all of the offsets would be wrong in the object file after
+	 * this segment. Instead we use the -pagezero_size option
+	 * to link the executable.
+	 */
+	if (msync(addr, 0x1000, MS_SYNC) == -1) {
+		(void)fprintf(stderr, "%s: could not sync %s: %s\n",
+				progname, argv[1], strerror(errno));
+		exit(1);
+	}
+
+	if (munmap(addr, 0x1000) == -1) {
+		(void)fprintf(stderr, "%s: could not unmap %s: %s\n",
+				progname, argv[1], strerror(errno));
+		exit(1);
+	}
+
+	(void)close(fd);
+
+	exit(0);
+}

BasiliskII/src/Unix/Darwin/pagezero.c

@@ -0,0 +1,31 @@
+/*
+ *  pagezero.c - test to see if low memory globals can be accessed
+ *
+ *  Copyright (c) 2003 Michael Z. Sliczniak
+ *
+ *  Basilisk II (C) 1997-2003 Christian Bauer
+ *
+ *  This program 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 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+int
+main(int argc, const char *argv[])
+{
+	volatile char *pagezero = (void *)0;
+
+	pagezero[0x1234] = pagezero[0x123];
+
+	return (0);
+}

BasiliskII/src/Unix/Darwin/testlmem.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+
+#  testlmem.sh - test whether the Mach-O hack works
+#
+#  Basilisk II (C) 1997-2003 Christian Bauer
+#
+#  testlmem.sh Copyright (C) 2003 Michael Z. Sliczniak
+#
+#  This program 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 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program 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.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+PAGEZERO_SIZE=0x2000
+[[ -n "$1" ]] && PAGEZERO_SIZE=$1
+# You want all the output to go to stderr so that configure is quiet but
+# config.log is verbose.
+{ echo 'building lowmem utility' && \
+make -f /dev/null Darwin/lowmem && \
+echo 'building pagezero test' && \
+make -f /dev/null LDFLAGS="-pagezero_size $PAGEZERO_SIZE" Darwin/pagezero && \
+echo 'enabling low memory globals in pagezero' && \
+Darwin/lowmem Darwin/pagezero && \
+echo 'running pagezero test' && \
+Darwin/pagezero; } 1>&2

BasiliskII/src/Unix/Makefile.in

@@ -23,6 +23,7 @@ LDFLAGS = @LDFLAGS@
 LIBS = @LIBS@
 SYSSRCS = @SYSSRCS@
 CPUSRCS = @CPUSRCS@
+BLESS = @BLESS@
 INSTALL = @INSTALL@
 INSTALL_PROGRAM = @INSTALL_PROGRAM@ -s
 INSTALL_DATA = @INSTALL_DATA@
@@ -61,6 +62,7 @@ VPATH += $(addprefix :, $(subst  ,:, $(filter-out $($(subst, :, ,$(VPATH))), $(S
 
 $(APP): $(OBJ_DIR) $(OBJS)
 	$(CXX) -o $(APP) $(LDFLAGS) $(OBJS) $(LIBS)
+	$(BLESS) $(APP)
 
 modules:
 	cd Linux/NetDriver; make

BasiliskII/src/Unix/configure.ac

@@ -558,6 +558,19 @@ AC_TRANSLATE_DEFINE(HAVE_MMAP_VM, $have_mmap_vm,
 
 fi dnl HAVE_MMAP_VM
 
+dnl Check if we can modify the __PAGEZERO segment for use as Low Memory
+AC_CACHE_CHECK([whether __PAGEZERO can be Low Memory area 0x0000-0x2000],
+  ac_cv_pagezero_hack, [
+  ac_cv_pagezero_hack=no 
+  if AC_TRY_COMMAND([Darwin/testlmem.sh 0x2000]); then
+    ac_cv_pagezero_hack=yes
+    dnl might as well skip the test for mmap-able low memory
+    ac_cv_can_map_lm=no
+  fi
+])
+AC_TRANSLATE_DEFINE(PAGEZERO_HACK, "$ac_cv_pagezero_hack",
+  [Define if the __PAGEZERO Mach-O Low Memory Globals hack works on this system.])
+
 dnl Check if we can mmap 0x2000 bytes from 0x0000
 AC_CACHE_CHECK([whether we can map Low Memory area 0x0000-0x2000],
   ac_cv_can_map_lm, [
@@ -743,6 +756,9 @@ if [[ -n "$sigsegv_recovery" ]]; then
   CAN_VOSF=yes
 fi
 
+dnl A dummy program that returns always true
+BLESS=/bin/true
+
 dnl Determine the addressing mode to use
 if [[ "x$WANT_NATIVE_M68K" = "xyes" ]]; then
   ADDRESSING_MODE="real"
@@ -753,10 +769,10 @@ else
     case $am in
     real)
       dnl Requires ability to mmap() Low Memory globals
-      if [[ "x$ac_cv_can_map_lm" = "xno" ]]; then
+      if [[ "x$ac_cv_can_map_lm$ac_cv_pagezero_hack" = "xnono" ]]; then
         continue
       fi
-	  dnl Requires VOSF screen updates
+      dnl Requires VOSF screen updates
       if [[ "x$CAN_VOSF" = "xno" ]]; then
         continue
       fi
@@ -764,6 +780,10 @@ else
       ADDRESSING_MODE="real"
       WANT_VOSF=yes dnl we can use VOSF and we need it actually
       DEFINES="$DEFINES -DREAL_ADDRESSING"
+      if [[ "x$ac_cv_pagezero_hack" = "xyes" ]]; then
+        BLESS=Darwin/lowmem
+        LDFLAGS="$LDFLAGS -pagezero_size 0x2000"
+      fi
       break
       ;;
     direct)
@@ -1152,6 +1172,7 @@ AC_SUBST(DEFINES)
 AC_SUBST(SYSSRCS)
 AC_SUBST(CPUINCLUDES)
 AC_SUBST(CPUSRCS)
+AC_SUBST(BLESS)
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT
 

BasiliskII/src/Unix/main_unix.cpp

@@ -413,7 +413,7 @@ int main(int argc, char **argv)
 	
 	// Under Solaris/SPARC and NetBSD/m68k, Basilisk II is known to crash
 	// when trying to map a too big chunk of memory starting at address 0
-#if defined(OS_solaris) || defined(OS_netbsd)
+#if defined(OS_solaris) || defined(OS_netbsd) || defined(PAGEZERO_HACK)
 	const bool can_map_all_memory = false;
 #else
 	const bool can_map_all_memory = true;
@@ -425,6 +425,7 @@ int main(int argc, char **argv)
 		memory_mapped_from_zero = true;
 	}
 	
+#ifndef PAGEZERO_HACK
 	// Otherwise, just create the Low Memory area (0x0000..0x2000)
 	else if (vm_acquire_fixed(0, 0x2000) == 0) {
 		D(bug("Could allocate the Low Memory globals\n"));
@@ -438,6 +439,7 @@ int main(int argc, char **argv)
 		QuitEmulator();
 	}
 #endif
+#endif /* REAL_ADDRESSING */
 
 	// Create areas for Mac RAM and ROM
 #if REAL_ADDRESSING