From 5c3580e9b58f28a4ede1b26093daeb1d97b1ce2d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juhani=20Krekel=C3=A4?= <juhani@krekelä.fi>
Date: Sun, 19 Mar 2023 19:28:30 +0200
Subject: [PATCH] Get rid of syscall thunks

---
 .gitignore            |  1 +
 Makefile              |  9 ++++++---
 add_syscalls.py       | 47 +++++++++++++++++++++++++++++++++++++++++++
 ponydos.asm           | 29 +++++++++++---------------
 ponydos.inc           |  9 ---------
 ponydos_nosyscall.inc |  5 +++++
 process_wallpaper.py  |  6 +++---
 7 files changed, 74 insertions(+), 32 deletions(-)
 create mode 100644 add_syscalls.py
 delete mode 100644 ponydos.inc
 create mode 100644 ponydos_nosyscall.inc

diff --git a/.gitignore b/.gitignore
index 7cf5001..1881db6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 *.bin
 *.img
+ponydos.inc
diff --git a/Makefile b/Makefile
index d431d3b..245bed2 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,10 @@ FS_FILES = wallpaper.bin shell.bin
 ponydos.img: ponydos.bin $(FS_FILES)
 	$(PYTHON) assemble_floppy.py $@ ponydos.bin $(FS_FILES)
 
-ponydos.bin: ponydos.inc
+ponydos.inc: ponydos.asm ponydos_nosyscall.inc
+	$(NASM) -fbin -d SYMBOLS -o /dev/null ponydos.asm | $(PYTHON) add_syscalls.py $@ ponydos_nosyscall.inc
+
+ponydos.bin: ponydos_nosyscall.inc
 
 shell.bin: ponydos.inc
 
@@ -19,13 +22,13 @@ shell.bin: ponydos.inc
 	$(NASM) -fbin -o $@ $<
 
 .ansi.bin:
-	$(PYTHON) process_wallpaper.py $< $@ 7 0 0 0
+	$(PYTHON) process_wallpaper.py $@ $< 7 0 0 0
 
 run: ponydos.img
 	qemu-system-i386 -fda $<
 
 clean:
-	rm -f *.bin *.img
+	rm -f *.bin *.img ponydos.inc
 
 distclean: clean
 
diff --git a/add_syscalls.py b/add_syscalls.py
new file mode 100644
index 0000000..3ae4028
--- /dev/null
+++ b/add_syscalls.py
@@ -0,0 +1,47 @@
+import sys
+
+syscalls = {
+	'open_file': None,
+	'read_sectors': None,
+	'draw_rect': None,
+}
+
+if len(sys.argv) != 3:
+	print(f'Usage: {sys.argv[0]} outfile infile', file=sys.stderr)
+	sys.exit(1)
+
+outfile = sys.argv[1]
+infile = sys.argv[2]
+
+with open(infile, 'r') as f:
+	header = f.read()
+header = f'; This is from {infile}\n' + header
+
+mapfile = []
+while True:
+	try:
+		line = input()
+	except EOFError:
+		break
+	mapfile.append(line)
+
+section = None
+for line in mapfile:
+	line = line.split()
+	if len(line) == 4 and all(c == '-' for c in line[0]) and line[1] == 'Section' and all(c == '-' for c in line[3]):
+		section = line[2]
+	if section == '.text' and len(line) == 3:
+		address, _, name = line
+		if name in syscalls:
+			syscalls[name] = int(address, 16)
+
+header += f'\n;This was automatically generated\n'
+
+for syscall, address in syscalls.items():
+	if address is None:
+		print(f'{sys.argv[0]}: Error: syscall {syscall} not found', file=sys.stderr)
+		sys.exit(1)
+	header += f'SYS_{syscall.upper()} equ 0x{address:x}\n'
+
+with open(outfile, 'w') as f:
+	f.write(header)
diff --git a/ponydos.asm b/ponydos.asm
index 5e418e3..efd1a9f 100644
--- a/ponydos.asm
+++ b/ponydos.asm
@@ -1,4 +1,7 @@
-%include "ponydos.inc"
+%ifdef SYMBOLS
+[map symbols]
+%endif
+%include "ponydos_nosyscall.inc"
 
 cpu 286
 bits 16
@@ -14,17 +17,6 @@ FILE_MAX_SIZE equ 128
 
 jmp 0:start
 
-; Thunks for application programs to use
-; 0x7c05 SYS_OPEN_FILE
-call open_file
-retf
-; 0x7c09 SYS_READ_SECTORS
-call read_sectors
-retf
-; 0x7c0d SYS_DRAW_RECT
-call draw_rect
-retf
-
 start:
 	cld
 
@@ -81,9 +73,9 @@ load_shell:
 	push word 0x1000
 	pop es
 	mov si, shell_name
-	call open_file
+	call 0:open_file
 	xor bx, bx
-	call read_sectors
+	call 0:read_sectors
 	; TODO: error management? Surely this works...
 
 	xor ax, ax ; WM_INITIALIZE
@@ -134,6 +126,7 @@ mainloop:
 ;  ds:si = beginning of source data
 ;  di = X
 ;  bp = Y
+; [Far calls only]
 draw_rect:
 	pusha
 	push es
@@ -173,7 +166,7 @@ draw_rect:
 
 	pop es
 	popa
-	ret
+	retf
 
 ; requires:
 ;  ds = 0
@@ -224,6 +217,7 @@ flip_mouse_cursor:
 ;;  bl = drive number
 ;  cx = number of sectors to read (must be at least 1)
 ;  es:bx = output buffer
+; [Far calls only]
 read_sectors:
 	pusha
 
@@ -235,7 +229,7 @@ read_sectors:
 		loop .loop
 
 	popa
-	ret
+	retf
 
 ; in:
 ;  ax = LBA of first sector
@@ -291,6 +285,7 @@ shell_name db 'shell.bin', 0
 ; out:
 ;  ax = LBA of first sector, 0 if no space left
 ;  cx = length in sectors
+; [Far calls only]
 open_file:
 	push si
 	push di
@@ -343,7 +338,7 @@ open_file:
 	pop bx
 	pop di
 	pop si
-	ret
+	retf
 
 	.create_file:
 		; TODO: zero out the sector for this file?
diff --git a/ponydos.inc b/ponydos.inc
deleted file mode 100644
index 86b71fd..0000000
--- a/ponydos.inc
+++ /dev/null
@@ -1,9 +0,0 @@
-PONYDOS_SEG equ 0
-
-SYS_OPEN_FILE equ 0x7c05
-SYS_READ_SECTORS equ 0x7c09
-SYS_DRAW_RECT equ 0x7c0d
-
-GLOBAL_WALLPAPER equ 0x500
-
-WM_INITIALIZE equ 0
diff --git a/ponydos_nosyscall.inc b/ponydos_nosyscall.inc
new file mode 100644
index 0000000..487b2e0
--- /dev/null
+++ b/ponydos_nosyscall.inc
@@ -0,0 +1,5 @@
+PONYDOS_SEG equ 0
+
+GLOBAL_WALLPAPER equ 0x500
+
+WM_INITIALIZE equ 0
diff --git a/process_wallpaper.py b/process_wallpaper.py
index 45f11cf..78a9ed3 100644
--- a/process_wallpaper.py
+++ b/process_wallpaper.py
@@ -7,11 +7,11 @@ HEIGHT = 25
 color_map = [0, 4, 2, 6, 1, 5, 3, 7]
 
 if len(sys.argv) != 7:
-	print("Usage: {sys.argv[0]} infile outfile default_fgcolor default_bgcolor origin_x origin_y", file=sys.stderr)
+	print("Usage: {sys.argv[0]} outfile infile default_fgcolor default_bgcolor origin_x origin_y", file=sys.stderr)
 	sys.exit(1)
 
-infile = sys.argv[1]
-outfile = sys.argv[2]
+outfile = sys.argv[1]
+infile = sys.argv[2]
 
 default_fgcolor = int(sys.argv[3])
 assert 0 <= default_fgcolor <= 15