Support Dreamcasts with 32MB system RAM

Only the 9.3.0 patch is updated!

Author: tsowell

kernel/arch/dreamcast/include/arch/arch.h

@@ -136,6 +136,14 @@ void __crtend_pullin();
 */
 int mm_init();
 
+/** \brief  Determine how much addressable memory is present.  On Dreamcast
+	    this checks the MCR to determine which addressing is being used.
+	    Only supports pristine 16MB SDRAM and 32MB SDRAM as described at
+	    https://tsowell.github.io/2020/06/21/dreamcast-32mb-ram-upgrade.html
+    \return The address that forms the upper bound of system RAM.
+*/
+uint32 mm_top();
+
 /** \brief  Request more core memory from the system.
     \param  increment       The number of bytes requested.
     \return                 A pointer to the memory.
@@ -354,17 +362,13 @@ const char *kos_get_authors(void);
 */
 #define arch_fptr_next(fptr) (*((uint32*)(fptr+4)))
 
-#ifndef _arch_sub_naomi
 /** \brief  Returns true if the passed address is likely to be valid. Doesn't
             have to be exact, just a sort of general idea.
 
     \return                 Whether the address is valid or not for normal
                             memory access.
 */
-#define arch_valid_address(ptr) ((ptr_t)(ptr) >= 0x8c010000 && (ptr_t)(ptr) < 0x8d000000)
-#else
-#define arch_valid_address(ptr) ((ptr_t)(ptr) >= 0x8c010000 && (ptr_t)(ptr) < 0x8e000000)
-#endif
+#define arch_valid_address(ptr) ((ptr_t)(ptr) >= 0x8c010000 && (ptr_t)(ptr) < mm_top())
 
 __END_DECLS
 

kernel/arch/dreamcast/kernel/mm.c

@@ -19,6 +19,8 @@
 #include <arch/irq.h>
 #include <stdio.h>
 
+#define MCR (*((volatile uint32_t *) 0xff800014))
+
 /* The end of the program is always marked by the '_end' symbol. So we'll
    longword-align that and add a little for safety. sbrk() calls will
    move up from there. */
@@ -34,6 +36,21 @@ int mm_init() {
     return 0;
 }
 
+/* Return address at top of system RAM */
+uint32 mm_top() {
+	if (((MCR >> 3) & 0x07) == 3) {
+		/* AMX 3, assuming 32MB SDRAM */
+		return 0x8e000000;
+	}
+	else {
+#ifndef _arch_sub_naomi
+		return 0x8d000000;
+#else
+		return 0x8e000000;
+#endif
+	}
+}
+
 /* Simple sbrk function */
 void* mm_sbrk(unsigned long increment) {
     int old;
@@ -46,7 +63,7 @@ void* mm_sbrk(unsigned long increment) {
 
     sbrk_base = (void *)(increment + (unsigned long)sbrk_base);
 
-    if(((uint32)sbrk_base) >= (0x8d000000 - 65536)) {
+    if(((uint32)sbrk_base) >= (mm_top() - 65536)) {
         dbglog(DBG_DEAD, "Requested sbrk_base %p, was %p, diff %lu\n",
                sbrk_base, base, increment);
         arch_panic("out of memory; about to run over kernel stack");

kernel/arch/dreamcast/kernel/stack.c

@@ -29,7 +29,7 @@ void arch_stk_trace_at(uint32 fp, int n) {
     dbgio_printf("-------- Stack Trace (innermost first) ---------\n");
 
     while(fp != 0xffffffff) {
-        if((fp & 3) || (fp < 0x8c000000) || (fp > 0x8d000000)) {
+        if((fp & 3) || (fp < 0x8c000000) || (fp > mm_top())) {
             dbgio_printf("   (invalid frame pointer)\n");
             break;
         }

kernel/arch/dreamcast/kernel/startup.s

@@ -71,7 +71,15 @@ init:
 	! Save the current stack, and set a new stack (higher up in RAM)
 	mov.l	old_stack_addr,r0
 	mov.l	r15,@r0
-	mov.l	new_stack,r15
+	! Set stack based on MCR
+        mov.l	new_stack_16m,r15
+	mov.l	mcr,r1
+	mov.l	@r1,r0
+	and	#0x38,r0
+	cmp/eq	#0x18,r0
+	bf	mcr_16m
+        mov.l	new_stack_32m,r15
+mcr_16m:
 
 	! Save VBR
 	mov.l	old_vbr_addr,r0
@@ -173,8 +181,12 @@ old_stack_addr:
 __arch_old_stack:
 old_stack:
 	.long	0
-new_stack:
+new_stack_16m:
 	.long	0x8d000000
+new_stack_32m:
+	.long	0x8e000000
+mcr:
+	.long	0xff800014
 p2_mask:
 	.long	0xa0000000
 setup_cache_addr:

kernel/mm/malloc_debug.c

@@ -108,7 +108,7 @@ void *malloc(size_t amt) {
     spinlock_unlock(&mutex);
 
     printf("Thread %d/%08lx allocated %d bytes at %08lx; %08lx left\n",
-           ctl->thread, ctl->addr, ctl->size, space, 0x8d000000 - (uint32)sbrk(0));
+           ctl->thread, ctl->addr, ctl->size, space, mm_top() - (uint32)sbrk(0));
 
     assert(!(((uint32)space) & 7));
 
@@ -178,7 +178,7 @@ void free(void *block) {
     printf("Thread %d/%08x freeing block @ %08x\n",
            thd_current->tid, pr, (uint32)block);
 
-    if(((uint32)block) & 7 || (uint32)block < 0x8c010000 || (uint32)block >= 0x8d000000) {
+    if(((uint32)block) & 7 || (uint32)block < 0x8c010000 || (uint32)block >= mm_top()) {
         printf("   ATTEMPT TO FREE INVALID ADDRESS!\n");
         spinlock_unlock(&mutex);
         return;

utils/dc-chain/patches/gcc-9.3.0-kos.diff

@@ -13,7 +13,7 @@ diff -ruN gcc-9.3.0/gcc/configure gcc-9.3.0-kos/gcc/configure
 diff -ruN gcc-9.3.0/libgcc/config/sh/crt1.S gcc-9.3.0-kos/libgcc/config/sh/crt1.S
 --- gcc-9.3.0/libgcc/config/sh/crt1.S	2020-03-12 07:07:23.000000000 -0400
 +++ gcc-9.3.0-kos/libgcc/config/sh/crt1.S	2020-04-03 16:07:04.540000000 -0400
-@@ -1,724 +1,197 @@
+@@ -1,724 +1,209 @@
 -/* Copyright (C) 2000-2019 Free Software Foundation, Inc.
 -   This file was pretty much copied from newlib.
 +! KallistiOS ##version##
@@ -232,7 +232,15 @@ diff -ruN gcc-9.3.0/libgcc/config/sh/crt1.S gcc-9.3.0-kos/libgcc/config/sh/crt1.
 +	! Save the current stack, and set a new stack (higher up in RAM)
 +	mov.l	old_stack_addr,r0
 +	mov.l	r15,@r0
-+	mov.l	new_stack,r15
++	! Set stack based on MCR
++	mov.l   new_stack_16m,r15
++	mov.l   mcr,r1
++	mov.l   @r1,r0
++	and     #0x38,r0
++	cmp/eq  #0x18,r0
++	bf      mcr_16m
++	mov.l   new_stack_32m,r15
++mcr_16m:
 +
 +	! Save VBR
 +	mov.l	old_vbr_addr,r0
@@ -896,8 +904,12 @@ diff -ruN gcc-9.3.0/libgcc/config/sh/crt1.S gcc-9.3.0-kos/libgcc/config/sh/crt1.
 +__arch_old_stack:
 +old_stack:
 +	.long	0
-+new_stack:
-+	.long	0x8d000000
++new_stack_16m:
++	.long   0x8d000000
++new_stack_32m:
++	.long   0x8e000000
++mcr:
++	.long   0xff800014
 +p2_mask:
 +	.long	0xa0000000
 +setup_cache_addr: