BOOT --bios: Execute the ROM BIOS after DOS kernel shutdown but do no…

…t treat it as a system reset signal. Load the BIOS image first into a temporary buffer and do not map until it is ready to execute to avoid crashes during DOS kernel shutdown triggered by BOOT --bios

CHANGELOG

@@ -1,4 +1,17 @@
 Next:
+  - BOOT --bios no longer triggers a system reset VM event, but instead just
+    jumps to the new BIOS image after DOS kernel shutdown. This is needed for
+    hardware and resources to stay as they were when running the BIOS i.e.
+    keeping any IDE devices configured within the DOS kernel intact so that the
+    BIOS can find and use them. Prior to this change, all hardware was fully
+    reset and unmapped prior to running the BIOS which made IDE emulation
+    unusable with BIOS images. (joncampbell123).
+  - BOOT --bios no longer immediately loads the new BIOS into memory, but instead
+    loads and stores the image to a temporary buffer. The ROM image does not
+    actually get mapped in until the DOS kernel and everything else has had a
+    chance to shut down fully. (joncampbell123).
+  - Fix BOOT --bios not to try to load PC-98 ITF firmware unless actually running
+    in PC-98 mode (joncampbell123).
   - Write PC-98 keyboard translation table (non-shifted) in ROM BIOS and set the
     keyboard translation table pointer in the BIOS data area for "Nut Berry".
     This Nut Berry game also assumes lookup and translation tables exist at

src/dos/dos_programs.cpp

@@ -1637,6 +1637,9 @@ static void CFGTOOL_ProgramStart(Program * * make) {
 }
 
 extern bool custom_bios;
+extern size_t custom_bios_image_size;
+extern Bitu custom_bios_image_offset;
+extern unsigned char *custom_bios_image;
 extern uint32_t floppytype;
 extern bool boot_debug_break;
 extern Bitu BIOS_bootfail_code_offset;
@@ -2005,7 +2008,15 @@ class BOOT : public Program {
             Bitu segbase = 0x100000 - loadsz;
             LOG_MSG("Loading BIOS image %s to 0x%lx, 0x%lx bytes",bios.c_str(),(unsigned long)segbase,(unsigned long)loadsz);
             fseek(romfp, 0, SEEK_SET);
-            size_t readResult = fread(GetMemBase()+segbase,loadsz,1,romfp);
+
+            // To avoid crashes should any interrupt be called on the way to running the BIOS,
+            // don't actually map it in until it's good and ready to go.
+            if (custom_bios_image != NULL) delete[] custom_bios_image;
+            custom_bios_image_size = loadsz;
+            custom_bios_image_offset = segbase;
+            custom_bios_image = new unsigned char[custom_bios_image_size];
+
+            size_t readResult = fread(custom_bios_image,loadsz,1,romfp);
             fclose(romfp);
             if (readResult != 1) {
                 LOG(LOG_IO, LOG_ERROR) ("Reading error in Run\n");

src/gui/sdlmain.cpp

@@ -7520,6 +7520,9 @@ bool is_always_on_top(void) {
 }
 
 bool custom_bios = false;
+size_t custom_bios_image_size = 0;
+Bitu custom_bios_image_offset = 0;
+unsigned char *custom_bios_image = NULL;
 
 // OK why isn't this being set for Linux??
 #ifndef SDL_MAIN_NOEXCEPT
@@ -7643,6 +7646,8 @@ std::wstring win32_prompt_folder(const char *default_folder) {
 }
 #endif
 
+void CPU_OnReset(Section* sec);
+
 void DISP2_Init(uint8_t color), DISP2_Shut();
 //extern void UI_Init(void);
 void grGlideShutdown(void);
@@ -9298,13 +9303,15 @@ int main(int argc, char* argv[]) SDL_MAIN_NOEXCEPT {
         Reflect_Menu();
 #endif
 
+        bool run_bios;
         bool reboot_dos;
         bool run_machine;
         bool wait_debugger;
         bool reboot_machine;
         bool dos_kernel_shutdown;
 
 fresh_boot:
+        run_bios = false;
         reboot_dos = false;
         run_machine = false;
         wait_debugger = false;
@@ -9356,7 +9363,7 @@ int main(int argc, char* argv[]) SDL_MAIN_NOEXCEPT {
             else if (x == 8) { /* Booting to a BIOS, shutting down DOSBox-X BIOS */
                 LOG(LOG_MISC,LOG_DEBUG)("Emulation threw a signal to boot into BIOS image");
 
-                reboot_machine = true;
+                run_bios = true;
                 dos_kernel_shutdown = !dos_kernel_disabled; /* only if DOS kernel enabled */
             }
             else if (x == 9) { /* BIOS caught a JMP to F000:FFF0 without any other hardware reset signal */
@@ -9537,7 +9544,52 @@ int main(int argc, char* argv[]) SDL_MAIN_NOEXCEPT {
         Reflect_Menu();
 #endif
 
-        if (reboot_machine) {
+        if (run_bios) {
+            LOG_MSG("Running a custom BIOS");
+
+            boothax = BOOTHAX_NONE;
+            guest_msdos_LoL = 0;
+            guest_msdos_mcb_chain = 0;
+
+            void CPU_Snap_Back_Forget();
+            /* Shutdown everything. For shutdown to work properly we must force CPU to real mode */
+            CPU_Snap_Back_To_Real_Mode();
+            CPU_Snap_Back_Forget();
+
+            /* TODO: Should we tell the system? */
+
+            /* force the mapper to let go of all keys so that the host key is not stuck (Issue #1320) */
+            MAPPER_ReleaseAllKeys();
+            void MAPPER_LosingFocus(void);
+            MAPPER_LosingFocus();
+
+            if (custom_bios) {
+                if (custom_bios_image && custom_bios_image_size != 0 && custom_bios_image_offset != 0) {
+		    memcpy(GetMemBase()+custom_bios_image_offset,custom_bios_image,custom_bios_image_size);
+                }
+
+		if (custom_bios_image) delete[] custom_bios_image;
+
+                /* need to relocate BIOS allocations */
+                void ROMBIOS_InitForCustomBIOS(void);
+                ROMBIOS_InitForCustomBIOS();
+            }
+
+            CPU_OnReset(NULL);
+
+#if C_DEBUG
+            if (boot_debug_break) {
+                boot_debug_break = false;
+
+                Bitu DEBUG_EnableDebugger(void);
+                DEBUG_EnableDebugger();
+            }
+#endif
+
+            /* run again */
+            goto fresh_boot;
+        }
+        else if (reboot_machine) {
             LOG_MSG("Rebooting the system\n");
 
             boothax = BOOTHAX_NONE;