Fix disk/read write error handling and add int13h LBA BIOS extensions

.gitignore

@@ -2,5 +2,7 @@ bios.bin
 bios.lst
 tinyxms.sys
 tinyxms.lst
+quitemu.com
+quitemu.lst
 8086tiny
 hd.img

8086tiny.c

@@ -13,6 +13,7 @@
 #include <memory.h>
 #include <stdint.h>
 #include <stdlib.h>
+#include <errno.h>
 
 #define AMOUNT_XMS_HANDLES 32
 #define XMS_REPORTED_FREE (16 * 1024 * 1024)
@@ -355,6 +356,38 @@ code_to_utf8(unsigned char *const buffer,
 	return 3;
 }
 
+// read/write routine -- Joshua Hudson <joshudson@gmail.com> 2023
+unsigned char readwrite(int handle, unsigned char *buffer, unsigned char nsectors, char mopcode)
+{
+	if (nsectors == 0) return 0xFF; // not sure if right, DosBOX does this
+	ssize_t r;
+	size_t len = (size_t)nsectors << 9;
+	ssize_t(*rw)(int,unsigned char*,size_t) = (mopcode != 3) ? (ssize_t(*)(int,unsigned char*,size_t))read:(ssize_t(*)(int,unsigned char*,size_t))write;
+	while (((r = rw(handle, buffer, len)) > 0 || r < 0 && errno == EINTR)) {
+		if (r < 0) continue; // EINTR
+		buffer += (size_t)r;
+		if (!(len -= (size_t)r)) {
+			// All data transferred
+			if (mopcode == 3) {
+#ifndef _WIN32
+				if (fdatasync(handle)) break; // r will not be 0; switches on errno
+//#else I'd have to rewrite a whole lot to implement the call on Windows.
+#endif
+			}
+			return 0;
+		}
+		// Network FS had to chunk write down
+	}
+	// Error pathway
+	if (r == 0) return 0x04; // Sector not found
+	switch (errno) {
+		case ENODEV: case ENXIO: return 0xAA; // Drive not ready
+		case EBADF: case EROFS: return mopcode == 3 ? 0x03 /* write protected */ : 0x0A;
+		case ENOSPC: case EDQUOT: return 0x04; // sparce file and out of disk: best fit is no such sector
+		default: return 0x0A; // bad sector: it's EIO and there aren't many likely cases
+	}
+}
+
 // Emulator entry point
 int main(int argc, char **argv)
 {
@@ -810,9 +843,9 @@ int main(int argc, char **argv)
 						CAST(short)mem[SEGREG(REG_ES, REG_BX, 36+)] = ms_clock.millitm;
 					OPCODE 2: // DISK_READ
 					OPCODE_CHAIN 3: // DISK_WRITE
-						regs8[REG_AL] = ~lseek(disk[regs8[REG_DL]], CAST(unsigned)regs16[REG_BP] << 9, 0)
-							? ((char)i_data0 == 3 ? (int(*)())write : (int(*)())read)(disk[regs8[REG_DL]], mem + SEGREG(REG_ES, REG_BX,), regs16[REG_AX])
-							: 0;
+						regs8[REG_AH] = ~lseek(disk[regs8[REG_DL]], CAST(unsigned)regs16[REG_BP] << 9, 0)
+							? readwrite(disk[regs8[REG_DL]], mem + SEGREG(REG_ES, REG_BX,), regs8[REG_AL], (char)i_data0)
+							: (errno == EINVAL) ? 0x04 /* out of range on disk device */ : 0xAA /* no disk */;
 					OPCODE 4:	// XMS
 						callxms();
 				}
@@ -1055,7 +1088,8 @@ int main(int argc, char **argv)
 #ifndef NO_GRAPHICS
 	SDL_Quit();
 #endif
-	return 0;
+	// I really want to be able to pass an exit code out, but the pre-existing QUITEMU passes garbage. -JH
+	return (regs16[REG_BX] == 0x1234) ? regs8[REG_AL] : 0;
 }
 
 

Makefile

@@ -18,11 +18,14 @@ bios.bin: bios.asm
 tinyxms.sys: tinyxms.asm
 	nasm -f bin -I ../lmacros/ -I lmacros/ -l tinyxms.lst -o tinyxms.sys tinyxms.asm
 
-8086tiny: 8086tiny.c bios.bin tinyxms.sys
+quitemu.com: quitemu.asm
+	nasm -f bin -o quitemu.com quitemu.asm
+
+8086tiny: 8086tiny.c bios.bin tinyxms.sys quitemu.com
 	${CC} 8086tiny.c ${OPTS_SDL} ${OPTS_ALL} -o 8086tiny
 	strip 8086tiny
 
-8086tiny_slowcpu: 8086tiny.c bios.bin tinyxms.sys
+8086tiny_slowcpu: 8086tiny.c bios.bin tinyxms.sys quitemu.com
 	${CC} 8086tiny.c ${OPTS_SDL} ${OPTS_ALL} ${OPTS_SLOWCPU} -o 8086tiny
 	strip 8086tiny
 
@@ -31,4 +34,4 @@ no_graphics: 8086tiny.c bios.bin tinyxms.sys
 	strip 8086tiny
 
 clean:
-	rm -f 8086tiny bios.bin bios.lst tinyxms.sys tinyxms.lst
+	rm -f 8086tiny bios.bin bios.lst tinyxms.sys tinyxms.lst quitemu.com

bios.asm

@@ -55,7 +55,7 @@ main:
 	dw	flags_mult	; Table 19: FLAGS multipliers
 
 
-biosstr	db	'8086tiny BIOS Revision 1.62!', 0, 0
+biosstr	db	'8086tiny BIOS Revision 1.70!', 0, 0
 
 
 bios_entry:
@@ -2141,6 +2141,14 @@ int13:
 	je	int13_getdisktype
 	cmp	ah, 0x16 ; Detect disk change
 	je	int13_diskchange
+	cmp	ah, 0x41
+	je	int13_echeck
+	cmp	ah, 0x42
+	je	int13_eread_disk
+	cmp	ah, 0x43
+	je	int13_ewrite_disk
+	cmp	ah, 0x48
+	je	int13_eparam
 
 	mov	ah, 1 ; Invalid function
 	jmp	reach_stack_stc
@@ -2204,18 +2212,12 @@ int13:
 
 	call	chs_to_abs
 
-	; Now, SI:BP contains the absolute sector offset of the block. We then multiply by 512 to get the offset into the disk image
+	; Now, SI:BP contains the absolute sector offset of the block.
 
-	mov	ah, 0
-	cpu	186
-	shl	ax, 9
 	extended_read_disk
-	shr	ax, 9
-	cpu	8086
-	mov	ah, 0x02	; Put read code back
 
-	cmp	al, 0
-	je	rd_error
+	cmp	ah, 0
+	jne	rd_error
 
 	; Read was successful. Now, check if we have read the boot sector. If so, we want to update
 	; our internal table of sectors/track to match the disk format
@@ -2247,14 +2249,11 @@ int13:
 
     rd_noerror:
 
-	clc
-	mov	ah, 0 ; No error
-	jmp	rd_finish
+	db 0A8h			; test al, imm8 (NC, skip stc)
 
     rd_error:
 
 	stc
-	mov	ah, 4 ; Sector not found
 
     rd_finish:
 
@@ -2323,24 +2322,16 @@ int13:
 wr_fine:
 
 	mov	ah, 0
-	cpu	186
-	shl	ax, 9
 	extended_write_disk
-	shr	ax, 9
-	cpu	8086
-	mov	ah, 0x03	; Put write code back
 
-	cmp	al, 0
-	je	wr_error
+	cmp	ah, 0
+	jne	wr_error
 
-	clc
-	mov	ah, 0 ; No error
-	jmp	wr_finish
+	db 0A8h			; test al, imm8 (NC, skip stc)
 
     wr_error:
 
 	stc
-	mov	ah, 4 ; Sector not found
 
     wr_finish:
 
@@ -2451,6 +2442,148 @@ wr_fine:
 	mov	ah, 0 ; Disk not changed
 	jmp	reach_stack_clc
 
+;******************************************************************
+; INT 13h LBA Extensions - Joshua Hudson <joshudson@gmail.com> 2023
+
+  int13_echeck:
+
+	cmp	dl, 0x80
+	jne	int13_enofloppy
+	mov	ah, 0x20
+	mov	bx, 0xAA55
+	mov	cx, 1
+	jmp	reach_stack_clc
+
+  int13_enofloppy:		; Special version for int13_echeck: don't set disk status
+	mov	ah, 1
+	jmp	reach_stack_stc
+
+  int13_eread_disk:
+
+	cmp	dl, 0x80
+	jne	no_int13e
+	jmp	int13_ereadwrite_disk
+
+  int13_ewrite_disk:
+
+	cmp	dl, 0x80
+	jne	no_int13e
+	;; Phoenix BIOS had to disable and move write/verify because of messed-up callers
+	;; Don't look at low bit of AL to decide write verify or not. We can't implement anyway.
+	jmp	int13_ereadwrite_disk
+
+  int13_eparam:
+
+	cmp	dl, 0x80
+	jne	no_int13e
+	cmp	[si], word 0x1E
+	jne	no_int13e
+	push	ax
+	xor	ax, ax
+	mov	[si + 2], ax
+	mov	[si + 0x06], ax
+	mov	[si + 0x0A], ax
+	mov	[si + 0x0E], ax
+	mov	[si + 0x14], ax
+	mov	[si + 0x16], ax
+	mov	[si + 0x1A], ax
+	mov	[si + 0x1E], ax
+	mov	ax, [cs:hd_max_track]	; Not bothering to detranslate -- there's no ATA device to talk to
+	mov	[si + 0x04], ax
+	mov	ax, [cs:hd_max_head]
+	mov	[si + 0x08], ax
+	mov	ax, [cs:hd_max_sector]
+	mov	[si + 0x0C], ax
+	mov	ax, [cs:hd_secs_lo]
+	mov	[si + 0x10], ax
+	mov	ax, [cs:hd_secs_hi]
+	mov	[si + 0x12], ax
+	mov	[si + 0x18], word 512
+	pop	ax
+	mov	ah, 0
+	jmp	int13_eresult
+
+  no_int13e:				; Invalid function argument
+	mov	ah, 1
+  int13_eresult:
+	mov	[cs:disk_laststatus], ah
+	cmp	ah, 0
+	jne	int13_efail
+	jmp	reach_stack_clc
+  int13_efail:
+	jmp	reach_stack_stc
+
+  int13_ereadwrite_disk:
+
+	cmp	[si], byte 0x10
+	jne	no_int13e
+	cmp	[si + 3], byte 0
+	je	int13_erangeok
+	mov	ah, 0x0D
+	jmp	int13_eresult
+
+  int13_erangefail:
+
+	mov	ah, 0x04
+	jmp	int13_eresult
+
+  int13_erangeok:
+
+	cmp	[si + 12], word 0
+	jne	int13_erangefail
+	cmp	[si + 14], word 0
+	jne	int13_erangefail
+
+	push	dx
+	push	si
+	push	ax
+	push	bp
+	push	es
+	push	bx
+
+	mov	al, [si + 2]
+	mov	es, [si + 6]
+	mov	bx, [si + 4]
+	mov	bp, [si + 8]
+	mov	si, [si + 10]
+	mov	dl, 0		; Hard disk handle offset
+
+	cmp	si, [cs:hd_secs_hi]
+	jb	int13_erangeok2
+	ja	int13_erangefail2
+	cmp	bp, [cs:hd_secs_lo]
+	jae	int13_erangefail2
+
+  int13_erangeok2:
+	cmp	ah, 0x43
+	je	int13_ewritecall
+
+	extended_read_disk
+	jmp	int13_edecode
+
+  int13_ewritecall:
+
+	extended_write_disk
+	;jmp	int13_edecode
+
+  int13_edecode:
+
+	mov	dh, ah
+	pop	bx
+	pop	es
+	pop	bp
+	pop	ax
+	mov	ah, dh
+	pop	si
+	pop	dx
+
+	jmp	int13_eresult
+
+  int13_erangefail2:
+
+	mov	ah, 0x04
+	jmp	int13_edecode
+
 ; ************************* INT 14h - serial port functions
 
 int14:
@@ -3880,6 +4013,7 @@ int_table	dw int0
           	dw int1d
           	dw 0xf000
           	dw int1e
+          	dw 0xf000
 
 itbl_size equ $-int_table
 
@@ -4087,4 +4221,4 @@ tm_msec		equ $+36
 
 mem_top:
 	jmp 0F000h:100h
-	db '03/08/14', 0, 0xfe, 0
+	db '11/26/23', 0, 0xfe, 0

quitemu.asm

@@ -0,0 +1,40 @@
+CPU 8086
+
+BITS 16
+
+ORG 0x100
+
+	mov	si, 0x80
+	lodsb
+	mov	bl, al
+	mov	bh, 0
+	add	bx, si
+	mov	cl, 10
+	xor	dx, dx
+lop:
+	cmp	si, bx
+	je	go
+	lodsb
+	cmp	al, ' '
+	je	lop
+	cmp	al, 9
+	je	lop
+	sub	al, '0'
+	jb	help
+	cmp	al, 9
+	ja	help
+	xchg	ax, dx
+	mul	cl
+	add	al, dl
+	xchg	ax, dx
+	jmp	lop
+help:
+	mov	dx, msg
+	mov	ah, 9
+	int	21h
+	ret
+go:
+	xchg	ax, dx
+	mov	bx, 0x1234	; Tell emulator to use AL as exit code
+	jmp	0:0		; Actual enstruction that exits emulator
+msg	db	'Quits 8086tiny emulator', 13, 10, 'Usage: QUITEMU [exit code]', 13, 10, '$'