kernel: further support for the Math+ in general

* Add a new HWCALC value HWCALC_FXCG100, detected based on being on an
  Area-3 RAM model and having OS version that's either less than 3 or
  3 and built after January 2025.
* Disable the _ostk heap arena, as the region might simply not exist,
  and improve the VRAM allocation code to account for this better than
  the hardcoded macro previously in place for the fx-CP 400.
* Disable gint_osmenu() which can't work with MPM right now.
* Add BFile_FindFirst() and GetVRAMAddress() syscalls.

include/gint/hardware.h

@@ -111,6 +111,8 @@ void hw_detect(void);
 #define HWCALC_FX9860G_SLIM  7
 /* fx-CP 400 */
 #define HWCALC_FXCP400       8
+/* fx-CG 100, successor to the CG-50 in the Prizm family. Also Graph Math+ */
+#define HWCALC_FXCG100       9
 
 /*
 **  Keyboard

src/kernel/hardware.c

@@ -127,10 +127,28 @@ void hw_detect(void)
 	gint[HWCPUVR] = PVR;
 	gint[HWCPUPR] = PRR;
 
-	/* Tell Prizms apart from fx-CG 50 by checking the stack address*/
 	uint32_t stack;
 	__asm__("mov r15, %0" : "=r"(stack));
-	gint[HWCALC] = (stack < 0x8c000000) ? HWCALC_PRIZM : HWCALC_FXCG50;
+	char const *version = (void *)0x80020020;
+	char const *osdate = (void *)0x80b5ffe0;
+
+	/* Tell Prizms apart from fx-CG 50 by checking the stack address*/
+	if(stack < 0x8c000000) {
+		gint[HWCALC] = HWCALC_PRIZM;
+	}
+	/* Tell Math+/fx-CG 100 apart from CG-50 by checking OS version + date.
+	   CG-50 OS versions use OS 3. Math+, for some reason, rewinds back to OS 1
+	   and got updated to OS 2 in late 2024. We decide that we are on a CG-50 OS
+	   if the version is 3 and the date is 201x-2024. */
+	else {
+		/* All known CG-50 versions have date at this address due to the footer
+		   location. WARNING: not a future-proof address! */
+		char d0 = osdate[0], d1 = osdate[1], d2 = osdate[2], d3 = osdate[3];
+		bool cg50 = version[1] == '3' && d0 == '2' && d1 == '0' &&
+						(d2 == '1' || (d2 == '2' && d3 <= '4'));
+		gint[HWCALC] = cg50 ? HWCALC_FXCG50 : HWCALC_FXCG100;
+	}
+
 	gint[HWFS] = HWFS_FUGUE;
 
 	/* Tell the fx-CG emulator apart using the product ID */

src/kernel/kernel.c

@@ -118,16 +118,18 @@ void kinit(void)
 
 	/* Create an arena in the OS stack as well, for VRAM and more data */
 	#if GINT_HW_CG && !defined(GINT_NO_OS_STACK)
-	static kmalloc_arena_t os_stack = { 0 };
-	os_stack.name = "_ostk";
-	os_stack.is_default = true;
-	if(gint[HWCALC] == HWCALC_PRIZM || gint[HWCALC] == HWCALC_FXCG_MANAGER)
-		os_stack.start = (void *)0x880f0000;
-	else
-		os_stack.start = (void *)0x8c0f0000;
-	os_stack.end = os_stack.start + (350 * 1024);
-	kmalloc_init_arena(&os_stack, true);
-	kmalloc_add_arena(&os_stack);
+	if(gint[HWCALC] != HWCALC_FXCG100) {
+		static kmalloc_arena_t os_stack = { 0 };
+		os_stack.name = "_ostk";
+		os_stack.is_default = true;
+		if(gint[HWCALC] == HWCALC_PRIZM || gint[HWCALC] == HWCALC_FXCG_MANAGER)
+			os_stack.start = (void *)0x880f0000;
+		else
+			os_stack.start = (void *)0x8c0f0000;
+		os_stack.end = os_stack.start + (350 * 1024);
+		kmalloc_init_arena(&os_stack, true);
+		kmalloc_add_arena(&os_stack);
+	}
 	#endif
 
 	/* Allocate world buffers for the OS and for gint */

src/kernel/osmenu.c

@@ -95,6 +95,11 @@ static os_menu_function_t *find_os_menu_function(void)
 
 void gint_osmenu_native(void)
 {
+#if GINT_OS_CG
+	if(gint[HWCALC] == HWCALC_FXCG100)
+		return;
+#endif
+
 // TODO: OS menu on fx-CP
 #if !GINT_OS_CP
 	__ClearKeyBuffer();

src/kernel/start.c

@@ -42,8 +42,9 @@ int8_t gint_restart = 0;
 /* gint_setrestart(): Set whether to restart the add-in after exiting */
 void gint_setrestart(int restart)
 {
-	/* There is now return-to-menu so no restart on CP */
-	gint_restart = restart && !GINT_OS_CP;
+	/* No restart on the machines for which there is no return-to-menu, i.e. on
+	   fx-CP and on the fx-CG 100. */
+	gint_restart = restart && !GINT_OS_CP && gint[HWCALC] != HWCALC_FXCG100;
 }
 
 /* Return value of main() */

src/kernel/syscalls.S

@@ -217,7 +217,7 @@ _gint_get_CASIOWIN_API:
 	.long 0x1dab, 0x8024003c  /* BFile_GetPos */
 	.long 0x1daf, 0x8024025e  /* BFile_Write */
 	.long 0x1dac, 0x80240082  /* BFile_Read */
-	.long 0x1db6, 0           /* BFile_FindFirst */
+	.long 0x1db6, 0x80240888  /* BFile_FindFirst */
 	.long 0x1db8, 0x80240b06  /* BFile_FindNext */
 	.long 0x1dba, 0x80240c10  /* BFile_FindClose */
 	.long 0x08d9, 0x800b130c  /* Timer_Install */
@@ -227,7 +227,7 @@ _gint_get_CASIOWIN_API:
 	.long 0x12c6, 0           /* PutKeyCode */
 	.long 0x12bf, 0x8017be56  /* GetKeyWait */
 	.long 0x12c7, 0           /* ClearKeyBuffer */
-	.long 0x01e6, 0           /* GetVRAMAddress */
+	.long 0x01e6, 0x8004579a  /* GetVRAMAddress */
 	.long 0x1e6e, 0           /* SetQuitHandler */
 	.long 0x1839, 0           /* PowerOff */
 	.long 0x1187, 0           /* Reset */

src/render-cg/dvram.c

@@ -97,16 +97,15 @@ bool dvram_init(void)
 {
 	int const MARGIN = 32;
 
+	char const *arena = NULL;
+	if(kmalloc_get_arena("_ostk"))
+		arena = "_ostk";
+
 	/* Leave MARGIN bytes on each side of the region; this enables some
 	   important optimizations in the image renderer. We also add another
 	   32 bytes so we can manually 32-align the region */
-	uint32_t region = (uint32_t)kmalloc(DWIDTH*DHEIGHT*2 + MARGIN*2 + 32,
-#if !defined(GINT_NO_OS_STACK)
-		"_ostk"
-#else
-		NULL
-#endif
-	);
+	uint32_t region =
+		(uint32_t)kmalloc(DWIDTH*DHEIGHT*2 + MARGIN*2 + 32, arena);
 	if(region == 0)
 		return false;