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Add dosbox.conf option to write protect the DOSBox private area in UMB to deal with games that have fast and loose video rendering code that can corrupt that area

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Jonathan Campbell 2025-01-09 21:38:59 -08:00
parent 22b40f1732
commit 764389c829
7 changed files with 41 additions and 6 deletions
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8
contrib/windows/installer/dosbox-x.reference.setup.conf
View File

@ -605,7 +605,7 @@ convertdrivefat = true
# To fit a scaler in the resolution used at full screen may require a border or side bars.
# To fill the screen entirely, depending on your hardware, a different scaler/fullresolution might work.
# Scalers should work with most output options, but they are ignored for openglpp and TrueType font outputs.
# If you are using OpenGL/Direct3D shaders that need the exact pixels of the video output without scaling, set to hardware_none or hardware2x.
# If you are using OpenGL/Direct3D output and a shader that requires it, set to hardware_none or hardware2x.
# Possible values: none, normal2x, normal3x, normal4x, normal5x, advmame2x, advmame3x, advinterp2x, advinterp3x, hq2x, hq3x, 2xsai, super2xsai, supereagle, tv2x, tv3x, rgb2x, rgb3x, scan2x, scan3x, gray, gray2x, hardware_none, hardware2x, hardware3x, hardware4x, hardware5x, xbrz, xbrz_bilinear.
# glshader: Path to GLSL shader source to use with OpenGL output ("none" to disable, or "default" for default shader).
# Can be either an absolute path, a file in the "glshaders" subdirectory of the DOSBox-X configuration directory, or one of the built-in shaders (e.g. "sharp" for the pixel-perfect scaling mode):
@ -2338,6 +2338,9 @@ timeout = 0
#DOSBOX-X-ADV:# Possible values: true, false, 1, 0, auto.
#DOSBOX-X-ADV:# private area in umb: If set, keep private DOS segment in upper memory block, usually segment 0xC800 (Mainline DOSBox behavior)
#DOSBOX-X-ADV:# If clear, place private DOS segment at the base of system memory (just below the MCB)
#DOSBOX-X-ADV:# private area write protect: If set, prevent the guest from writing to the DOSBox private area. The emulator itself can still write to it, of course.
#DOSBOX-X-ADV:# Some DOS games have sloppy video routines that can spill over and corrupt the private area and cause problems.
#DOSBOX-X-ADV:# This option when set can prevent that errant game from causing crashes.
# quick reboot: If set, the DOS restart call will reboot the emulated DOS (integrated DOS or guest DOS) instead of the virtual machine.
#
# ver: Set DOS version. Specify as major.minor format. A single number is treated as the major version (compatible with LFN support). Common settings are:
@ -2444,7 +2447,7 @@ timeout = 0
# dos idle api: If set, DOSBox-X can lower the host system's CPU load when a supported guest program is idle.
#DOSBOX-X-ADV-SEE:#
#DOSBOX-X-ADV-SEE:# Advanced options (see full configuration reference file [dosbox-x.reference.full.conf] for more details):
#DOSBOX-X-ADV-SEE:# -> xms memmove causes flat real mode; xms init causes flat real mode; resized free memory block becomes allocated; badcommandhandler; mscdex device name; hma allow reservation; command shell flush keyboard buffer; special operation file prefix; drive z is remote; drive z convert fat; drive z expand path; drive z hide files; automount drive directories; hidenonrepresentable; hma minimum allocation; dos sda size; hma free space; cpm compatibility mode; minimum dos initial private segment; minimum mcb segment; enable dummy device mcb; maximum environment block size on exec; additional environment block size on exec; enable a20 on windows init; zero memory on xms memory allocation; vcpi; unmask timer on disk io; zero int 67h if no ems; zero unused int 68h; emm386 startup active; zero memory on ems memory allocation; ems system handle memory size; ems system handle on even megabyte; ems frame; umb start; umb end; kernel allocation in umb; keep umb on boot; keep private area on boot; private area in umb; autoa20fix; autoloadfix; startincon; int33 max x; int33 max y; int33 xy adjust; int33 mickey threshold; int33 hide host cursor if interrupt subroutine; int33 hide host cursor when polling; int33 disable cell granularity; int 13 disk change detect; int 13 extensions; biosps2; int15 wait force unmask irq; int15 mouse callback does not preserve registers; filenamechar; collating and uppercase; con device use int 16h to detect keyboard input; zero memory on int 21h memory allocation; pipe temporary device
#DOSBOX-X-ADV-SEE:# -> xms memmove causes flat real mode; xms init causes flat real mode; resized free memory block becomes allocated; badcommandhandler; mscdex device name; hma allow reservation; command shell flush keyboard buffer; special operation file prefix; drive z is remote; drive z convert fat; drive z expand path; drive z hide files; automount drive directories; hidenonrepresentable; hma minimum allocation; dos sda size; hma free space; cpm compatibility mode; minimum dos initial private segment; minimum mcb segment; enable dummy device mcb; maximum environment block size on exec; additional environment block size on exec; enable a20 on windows init; zero memory on xms memory allocation; vcpi; unmask timer on disk io; zero int 67h if no ems; zero unused int 68h; emm386 startup active; zero memory on ems memory allocation; ems system handle memory size; ems system handle on even megabyte; ems frame; umb start; umb end; kernel allocation in umb; keep umb on boot; keep private area on boot; private area in umb; private area write protect; autoa20fix; autoloadfix; startincon; int33 max x; int33 max y; int33 xy adjust; int33 mickey threshold; int33 hide host cursor if interrupt subroutine; int33 hide host cursor when polling; int33 disable cell granularity; int 13 disk change detect; int 13 extensions; biosps2; int15 wait force unmask irq; int15 mouse callback does not preserve registers; filenamechar; collating and uppercase; con device use int 16h to detect keyboard input; zero memory on int 21h memory allocation; pipe temporary device
#DOSBOX-X-ADV-SEE:#
xms = true
#DOSBOX-X-ADV:xms memmove causes flat real mode = true
@ -2500,6 +2503,7 @@ umb = true
#DOSBOX-X-ADV:keep umb on boot = false
#DOSBOX-X-ADV:keep private area on boot = auto
#DOSBOX-X-ADV:private area in umb = true
#DOSBOX-X-ADV:private area write protect = false
quick reboot = false
ver =
lfn = auto

4
dosbox-x.reference.conf
View File

@ -295,7 +295,7 @@ convertdrivefat = true
# To fit a scaler in the resolution used at full screen may require a border or side bars.
# To fill the screen entirely, depending on your hardware, a different scaler/fullresolution might work.
# Scalers should work with most output options, but they are ignored for openglpp and TrueType font outputs.
# If you are using OpenGL/Direct3D shaders that need the exact pixels of the video output without scaling, set to hardware_none or hardware2x.
# If you are using OpenGL/Direct3D output and a shader that requires it, set to hardware_none or hardware2x.
# Possible values: none, normal2x, normal3x, normal4x, normal5x, advmame2x, advmame3x, advinterp2x, advinterp3x, hq2x, hq3x, 2xsai, super2xsai, supereagle, tv2x, tv3x, rgb2x, rgb3x, scan2x, scan3x, gray, gray2x, hardware_none, hardware2x, hardware3x, hardware4x, hardware5x, xbrz, xbrz_bilinear.
# glshader: Path to GLSL shader source to use with OpenGL output ("none" to disable, or "default" for default shader).
# Can be either an absolute path, a file in the "glshaders" subdirectory of the DOSBox-X configuration directory, or one of the built-in shaders (e.g. "sharp" for the pixel-perfect scaling mode):
@ -1164,7 +1164,7 @@ timeout = 0
# dos idle api: If set, DOSBox-X can lower the host system's CPU load when a supported guest program is idle.
#
# Advanced options (see full configuration reference file [dosbox-x.reference.full.conf] for more details):
# -> xms memmove causes flat real mode; xms init causes flat real mode; resized free memory block becomes allocated; badcommandhandler; mscdex device name; hma allow reservation; command shell flush keyboard buffer; special operation file prefix; drive z is remote; drive z convert fat; drive z expand path; drive z hide files; automount drive directories; hidenonrepresentable; hma minimum allocation; dos sda size; hma free space; cpm compatibility mode; minimum dos initial private segment; minimum mcb segment; enable dummy device mcb; maximum environment block size on exec; additional environment block size on exec; enable a20 on windows init; zero memory on xms memory allocation; vcpi; unmask timer on disk io; zero int 67h if no ems; zero unused int 68h; emm386 startup active; zero memory on ems memory allocation; ems system handle memory size; ems system handle on even megabyte; ems frame; umb start; umb end; kernel allocation in umb; keep umb on boot; keep private area on boot; private area in umb; autoa20fix; autoloadfix; startincon; int33 max x; int33 max y; int33 xy adjust; int33 mickey threshold; int33 hide host cursor if interrupt subroutine; int33 hide host cursor when polling; int33 disable cell granularity; int 13 disk change detect; int 13 extensions; biosps2; int15 wait force unmask irq; int15 mouse callback does not preserve registers; filenamechar; collating and uppercase; con device use int 16h to detect keyboard input; zero memory on int 21h memory allocation; pipe temporary device
# -> xms memmove causes flat real mode; xms init causes flat real mode; resized free memory block becomes allocated; badcommandhandler; mscdex device name; hma allow reservation; command shell flush keyboard buffer; special operation file prefix; drive z is remote; drive z convert fat; drive z expand path; drive z hide files; automount drive directories; hidenonrepresentable; hma minimum allocation; dos sda size; hma free space; cpm compatibility mode; minimum dos initial private segment; minimum mcb segment; enable dummy device mcb; maximum environment block size on exec; additional environment block size on exec; enable a20 on windows init; zero memory on xms memory allocation; vcpi; unmask timer on disk io; zero int 67h if no ems; zero unused int 68h; emm386 startup active; zero memory on ems memory allocation; ems system handle memory size; ems system handle on even megabyte; ems frame; umb start; umb end; kernel allocation in umb; keep umb on boot; keep private area on boot; private area in umb; private area write protect; autoa20fix; autoloadfix; startincon; int33 max x; int33 max y; int33 xy adjust; int33 mickey threshold; int33 hide host cursor if interrupt subroutine; int33 hide host cursor when polling; int33 disable cell granularity; int 13 disk change detect; int 13 extensions; biosps2; int15 wait force unmask irq; int15 mouse callback does not preserve registers; filenamechar; collating and uppercase; con device use int 16h to detect keyboard input; zero memory on int 21h memory allocation; pipe temporary device
#
xms = true
xms handles = 0

6
dosbox-x.reference.full.conf
View File

@ -593,7 +593,7 @@ enable pci bus = true
# To fit a scaler in the resolution used at full screen may require a border or side bars.
# To fill the screen entirely, depending on your hardware, a different scaler/fullresolution might work.
# Scalers should work with most output options, but they are ignored for openglpp and TrueType font outputs.
# If you are using OpenGL/Direct3D shaders that need the exact pixels of the video output without scaling, set to hardware_none or hardware2x.
# If you are using OpenGL/Direct3D output and a shader that requires it, set to hardware_none or hardware2x.
# Possible values: none, normal2x, normal3x, normal4x, normal5x, advmame2x, advmame3x, advinterp2x, advinterp3x, hq2x, hq3x, 2xsai, super2xsai, supereagle, tv2x, tv3x, rgb2x, rgb3x, scan2x, scan3x, gray, gray2x, hardware_none, hardware2x, hardware3x, hardware4x, hardware5x, xbrz, xbrz_bilinear.
# glshader: Path to GLSL shader source to use with OpenGL output ("none" to disable, or "default" for default shader).
# Can be either an absolute path, a file in the "glshaders" subdirectory of the DOSBox-X configuration directory, or one of the built-in shaders (e.g. "sharp" for the pixel-perfect scaling mode):
@ -2278,6 +2278,9 @@ timeout = 0
# Possible values: true, false, 1, 0, auto.
# private area in umb: If set, keep private DOS segment in upper memory block, usually segment 0xC800 (Mainline DOSBox behavior)
# If clear, place private DOS segment at the base of system memory (just below the MCB)
# private area write protect: If set, prevent the guest from writing to the DOSBox private area. The emulator itself can still write to it, of course.
# Some DOS games have sloppy video routines that can spill over and corrupt the private area and cause problems.
# This option when set can prevent that errant game from causing crashes.
# quick reboot: If set, the DOS restart call will reboot the emulated DOS (integrated DOS or guest DOS) instead of the virtual machine.
#
# ver: Set DOS version. Specify as major.minor format. A single number is treated as the major version (compatible with LFN support). Common settings are:
@ -2436,6 +2439,7 @@ kernel allocation in umb = false
keep umb on boot = false
keep private area on boot = auto
private area in umb = true
private area write protect = false
quick reboot = false
ver =
lfn = auto

1
include/dos_inc.h
View File

@ -324,6 +324,7 @@ bool DOS_ResizeMemory(uint16_t segment,uint16_t * blocks);
bool DOS_FreeMemory(uint16_t segment);
void DOS_FreeProcessMemory(uint16_t pspseg);
uint16_t DOS_GetMemory(uint16_t pages,const char *who=NULL);
void DOS_Private_UMB_Lock(const bool lock);
void DOS_FreeTableMemory();
bool DOS_SetMemAllocStrategy(uint16_t strat);
uint16_t DOS_GetMemAllocStrategy(void);

2
src/dos/dos.cpp
View File

@ -3480,6 +3480,7 @@ static Bitu DOS_26Handler(void) {
return DOS_26Handler_Actual(false);
}
bool private_segment_write_protect = false;
bool enable_collating_uppercase = true;
bool keep_private_area_on_boot = false;
bool private_always_from_umb = false;
@ -4148,6 +4149,7 @@ public:
minimum_mcb_free = section->Get_hex("minimum mcb free");
minimum_mcb_segment = section->Get_hex("minimum mcb segment");
private_segment_in_umb = section->Get_bool("private area in umb");
private_segment_write_protect = section->Get_bool("private area write protect");
enable_collating_uppercase = section->Get_bool("collating and uppercase");
private_always_from_umb = section->Get_bool("kernel allocation in umb");
minimum_dos_initial_private_segment = section->Get_hex("minimum dos initial private segment");

21
src/dos/dos_tables.cpp
View File

@ -31,6 +31,7 @@ extern int maxfcb;
extern bool gbk, chinasea;
extern Bitu DOS_PRIVATE_SEGMENT_Size;
extern uint16_t desired_ems_segment;
extern bool private_segment_write_protect;
#if defined(USE_TTF)
extern bool ttf_dosv;
#endif
@ -103,6 +104,20 @@ bool DOS_User_Wants_UMBs() {
bool EMS_Active(void);
void Update_Get_Desired_Segment(void);
/* Some DOS games and demoscene stuff has fast and loose VRAM rendering code that can spill
* past video RAM into whatever follows in C0000h. If the DOSBox private area is there, then
* that sloppiness will corrupt whatever data structures and interrupts we put there and
* cause crashes. To prevent that, we allow write-protecting the area (DOSBox-X can still
* write to it using phys_writeb). */
void DOS_Private_UMB_Lock(const bool lock) {
if (DOS_PRIVATE_SEGMENT >= 0xA000) {
if (lock)
MEM_map_ROM_physmem((Bitu)DOS_PRIVATE_SEGMENT<<4u,((Bitu)DOS_PRIVATE_SEGMENT_END<<4u)-1u);
else
MEM_map_RAM_physmem((Bitu)DOS_PRIVATE_SEGMENT<<4u,((Bitu)DOS_PRIVATE_SEGMENT_END<<4u)-1u);
}
}
void DOS_GetMemory_Choose() {
if (DOS_PRIVATE_SEGMENT == 0) {
/* DOSBox-X non-compatible: Position ourself just past the VGA BIOS */
@ -145,7 +160,11 @@ void DOS_GetMemory_Choose() {
if (DOS_PRIVATE_SEGMENT >= 0xA000) {
memset(GetMemBase()+((Bitu)DOS_PRIVATE_SEGMENT<<4u),0x00,(Bitu)(DOS_PRIVATE_SEGMENT_END-DOS_PRIVATE_SEGMENT)<<4u);
MEM_map_RAM_physmem((Bitu)DOS_PRIVATE_SEGMENT<<4u,((Bitu)DOS_PRIVATE_SEGMENT_END<<4u)-1u);
if (private_segment_write_protect)
MEM_map_ROM_physmem((Bitu)DOS_PRIVATE_SEGMENT<<4u,((Bitu)DOS_PRIVATE_SEGMENT_END<<4u)-1u);
else
MEM_map_RAM_physmem((Bitu)DOS_PRIVATE_SEGMENT<<4u,((Bitu)DOS_PRIVATE_SEGMENT_END<<4u)-1u);
}
LOG(LOG_DOSMISC,LOG_DEBUG)("DOS private segment set to 0x%04x-0x%04x",DOS_PRIVATE_SEGMENT,DOS_PRIVATE_SEGMENT_END-1);

5
src/dosbox.cpp
View File

@ -4700,6 +4700,11 @@ void DOSBOX_SetupConfigSections(void) {
Pbool->Set_help("If set, keep private DOS segment in upper memory block, usually segment 0xC800 (Mainline DOSBox behavior)\n"
"If clear, place private DOS segment at the base of system memory (just below the MCB)");
Pbool = secprop->Add_bool("private area write protect",Property::Changeable::WhenIdle,false);
Pbool->Set_help("If set, prevent the guest from writing to the DOSBox private area. The emulator itself can still write to it, of course.\n"
"Some DOS games have sloppy video routines that can spill over and corrupt the private area and cause problems.\n"
"This option when set can prevent that errant game from causing crashes.");
Pbool = secprop->Add_bool("quick reboot",Property::Changeable::WhenIdle,false);
Pbool->Set_help("If set, the DOS restart call will reboot the emulated DOS (integrated DOS or guest DOS) instead of the virtual machine.\n");
Pbool->SetBasic(true);