From 4c678ca21000f575095bbd0cc475c091dd709fc5 Mon Sep 17 00:00:00 2001
From: Tee-Kiah Chia <tkchia@users.noreply.github.com>
Date: Tue, 23 Mar 2021 16:31:11 +0000
Subject: [PATCH 1/8] Adding MS-DOS .com program support (msdos86). Still
 incomplete.

---
 build.lua                          |   1 +
 plat/msdos86/boot.s                | 145 +++++++++++++++++++++++++++++
 plat/msdos86/build-pkg.lua         |  25 +++++
 plat/msdos86/build-tools.lua       |  21 +++++
 plat/msdos86/descr                 |  86 +++++++++++++++++
 plat/msdos86/libsys/sys_initmain.c | 112 ++++++++++++++++++++++
 6 files changed, 390 insertions(+)
 create mode 100644 plat/msdos86/boot.s
 create mode 100644 plat/msdos86/build-pkg.lua
 create mode 100644 plat/msdos86/build-tools.lua
 create mode 100644 plat/msdos86/descr
 create mode 100644 plat/msdos86/libsys/sys_initmain.c

diff --git a/build.lua b/build.lua
index ccd113f1a..1b459fb52 100644
--- a/build.lua
+++ b/build.lua
@@ -11,6 +11,7 @@ vars.plats = {
 	"linux68k",
 	"linuxppc",
 	"linuxmips",
+	"msdos86",
 	"osx386",
 	"osxppc",
 	"pc86",
diff --git a/plat/msdos86/boot.s b/plat/msdos86/boot.s
new file mode 100644
index 000000000..56d424e1c
--- /dev/null
+++ b/plat/msdos86/boot.s
@@ -0,0 +1,145 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+begtext:
+	! Make sure we are running under MS-DOS 2 or above.
+	!
+	! While at it, also remember the actual DOS version, so that we know
+	! whether DOS gives us the program's name in the environment
+	! segment.  (DOS 3+ does; DOS 2.x does not.)
+	movb ah, 0x30
+	int 0x21
+	cmpb al, 2
+	xchg bx, ax
+	jc bad_sys
+
+	! Clear BSS.
+	mov di, begbss
+	mov cx, endbss+1
+	sub cx, di
+	shr cx, 1
+	xor ax, ax
+	cld
+	rep stosw
+
+	! Get the size of the environment variables plus (if present) the
+	! program name.  Also count the number of environment variables.
+	mov es, (0x002C)
+	xor di, di
+	! ax = 0 from above
+	cwd				! dx = count of env. vars.
+	mov cx, -1
+	scasb				! handle special case of empty env.
+	jz is_empty_env
+size_env:
+	inc dx
+	repnz scasb
+	scasb
+	jnz size_env
+is_empty_env:
+	cmpb bl, 2
+	jz no_argv0
+	scasw
+	repnz scasb
+no_argv0:
+
+	! Copy out the environment variables and (possibly) program name
+	! onto the stack.
+	mov si, di
+	dec si
+	and si, -2
+	std
+copy_env:
+	test si, si
+	eseg lodsw
+	push ax
+	jnz copy_env
+	mov cx, sp
+
+	! Reset DF and es properly.
+	cld
+	push ss
+	pop es
+
+	! Reserve space for argc and the argv and envp pointers on the
+	! stack.  These will be passed to __m_a_i_n later.
+	sub sp, 6
+	mov ax, sp
+
+	! Build up argc, argv[], and envp[].
+	push ax				! output buffer for argc, argv, envp
+	push bx				! MS-DOS version
+	push cx				! env. string data
+	push dx				! count of env. vars.
+	mov ax, 0x0080
+	push ax				! raw command line
+	call __sys_initmain
+	add sp, 10
+
+	! Bail out if something went wrong.
+	test ax, ax
+	jnz no_room
+
+	! argc, argv, and envp are now at the stack top.  Now go.
+	call __m_a_i_n
+	add sp, 6
+	push ax
+	call _exit
+
+bad_sys:
+	mov dx, bad_sys_msg
+dos_msg:
+	movb ah, 9
+	int 0x21
+	ret
+
+no_room:
+	mov dx, no_room_msg
+	call dos_msg
+	movb al, -1
+	jmp al_exit
+
+	! Exit.
+.define __exit
+.extern __exit
+.define EXIT
+.extern EXIT
+__exit:
+EXIT:
+	pop bx
+	pop ax
+al_exit:
+	movb ah, 0x4c
+	int 0x21
+
+! Define symbols at the beginning of our various segments, so that we can find
+! them. (Except .text, which has already been done.)
+
+.define begtext, begdata, begbss
+.sect .data;       begdata:
+.sect .rom;        begrom:
+.sect .bss;        begbss:
+
+.sect .rom
+
+! Some text messages.
+bad_sys_msg: .ascii 'Bad DOS$'
+no_room_msg: .ascii 'No room$'
+
+! Some magic data. All EM systems need these.
+
+.define .trppc, .ignmask, _errno
+.comm .trppc, 4
+.comm .ignmask, 4
+.comm _errno, 4
diff --git a/plat/msdos86/build-pkg.lua b/plat/msdos86/build-pkg.lua
new file mode 100644
index 000000000..29e141c4c
--- /dev/null
+++ b/plat/msdos86/build-pkg.lua
@@ -0,0 +1,25 @@
+include("plat/build.lua")
+
+ackfile {
+	name = "boot",
+	srcs = { "./boot.s" },
+	vars = { plat = "msdos86" }
+}
+
+build_plat_libs {
+	name = "libs",
+	arch = "i86",
+	plat = "msdos86",
+}
+
+installable {
+	name = "pkg",
+	map = {
+		"+tools",
+		"+libs",
+        "./include+pkg",
+		["$(PLATIND)/msdos86/boot.o"] = "+boot",
+        ["$(PLATIND)/msdos86/libsys.a"] = "./libsys+lib",
+	}
+}
+
diff --git a/plat/msdos86/build-tools.lua b/plat/msdos86/build-tools.lua
new file mode 100644
index 000000000..53f1e2706
--- /dev/null
+++ b/plat/msdos86/build-tools.lua
@@ -0,0 +1,21 @@
+include("plat/build.lua")
+
+build_as {
+	name = "as",
+	arch = "i86",
+}
+
+build_ncg {
+	name = "ncg",
+	arch = "i86",
+}
+
+return installable {
+	name = "tools",
+	map = {
+		["$(PLATDEP)/msdos86/as"] = "+as",
+		["$(PLATDEP)/msdos86/ncg"] = "+ncg",
+		["$(PLATIND)/descr/msdos86"] = "./descr",
+		"util/opt+pkg",
+	}
+}
diff --git a/plat/msdos86/descr b/plat/msdos86/descr
new file mode 100644
index 000000000..97c05751b
--- /dev/null
+++ b/plat/msdos86/descr
@@ -0,0 +1,86 @@
+# $Source$
+# $State$
+# $Revision$
+
+var w=2
+var wa=2
+var p=2
+var pa=2
+var s=2
+var sa=2
+var l=4
+var la=2
+var f=4
+var fa=2
+var d=8
+var da=2
+var x=8
+var xa=2
+var ARCH=i86
+var PLATFORM=msdos86
+var PLATFORMDIR={EM}/share/ack/{PLATFORM}
+var CPP_F=-D__MSDOS__ -D__DOS__ -D_DOS
+var ALIGN=-a0:2 -a1:2 -a2:2 -a3:2
+var MACHOPT_F=-m8
+var EGO_PLAT_FLAGS=-M{EM}/share/ack/ego/{ARCH}.descr
+
+# Override the setting in fe so that files compiled for this platform can see
+# the platform-specific headers.
+
+var C_INCLUDES=-I{PLATFORMDIR}/include -I{EM}/share/ack/include/ansi
+
+# These will be overridden under the small (separate I/D) memory model.
+
+var SEPID=-b0:0x100
+var LOD=aslod
+
+name be
+	from .m.g
+	to .s
+	program {EM}/lib/ack/{PLATFORM}/ncg
+	args <
+	stdout
+	need .e
+end
+name as
+	from .s.so
+	to .o
+	program {EM}/lib/ack/{PLATFORM}/as
+	args - -o > <
+	prep cond
+end
+name led
+	from .o.a
+	to .out
+	program {EM}/lib/ack/em_led
+	mapflag -l* LNAME={PLATFORMDIR}/lib*
+	mapflag -i SEPID=-b1:0
+	mapflag -fp FLOATS={EM}/{ILIB}fp
+	args {ALIGN} {SEPID} \
+		({RTS}:.b=-u _i_main) \
+	    (.e:{HEAD}={PLATFORMDIR}/boot.o) \
+		({RTS}:.ocm.bas.b={PLATFORMDIR}/c-ansi.o) \
+		({RTS}:.c={PLATFORMDIR}/c-ansi.o) \
+		({RTS}:.mod={PLATFORMDIR}/modula2.o) \
+		({RTS}:.p={PLATFORMDIR}/pascal.o) \
+		-o > < \
+		(.p:{TAIL}={PLATFORMDIR}/libpascal.a) \
+		(.b:{TAIL}={PLATFORMDIR}/libb.a) \
+		(.bas:{TAIL}={PLATFORMDIR}/libbasic.a) \
+		(.mod:{TAIL}={PLATFORMDIR}/libmodula2.a) \
+		(.ocm:{TAIL}={PLATFORMDIR}/liboccam.a) \
+		(.ocm.bas.mod.b.c.p:{TAIL}={PLATFORMDIR}/libc.a) \
+		{FLOATS?} \
+		(.e:{TAIL}={PLATFORMDIR}/libem.a \
+		           {PLATFORMDIR}/libsys.a \
+		           {PLATFORMDIR}/libend.a)
+	linker
+end
+name cv
+	from .out
+	to .exe
+	mapflag -i LOD=amzlod
+	program {EM}/bin/{LOD}
+	args < >
+	outfile msdos86.exe
+end
diff --git a/plat/msdos86/libsys/sys_initmain.c b/plat/msdos86/libsys/sys_initmain.c
new file mode 100644
index 000000000..11b5a1fb4
--- /dev/null
+++ b/plat/msdos86/libsys/sys_initmain.c
@@ -0,0 +1,112 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define	OUT_OF_MEMORY (void*)(-1)	/* sbrk returns this on failure */
+
+struct for_main {
+	int argc;
+	char **argv;
+	char **envp;
+};
+
+/*
+ * Marshal the command line and environment variable data provided by
+ * MS-DOS, into the standard format expected by a C main(...) routine.  The
+ * environment variable data has been copied to the near data segment.
+ *
+ * Return zero if everything went well, non-zero otherwise.
+ */
+int _sys_initmain(char *arg_data, size_t n_env_vars, char *env_data,
+    unsigned msdos_ver, struct for_main *out)
+{
+	char **argv, **envp;
+	char c, *p, **pp;
+	unsigned char n;
+
+	/*
+	 * Allocate space for argv[] for the maximum possible number of
+	 * arguments.  We can shrink this later.
+	 */
+	if ((argv = sbrk(65 * sizeof(char *))) == OUT_OF_MEMORY)
+		return -1;
+	out->argv = argv;
+
+	/* Sanity-check the original command line. */
+	p = arg_data;
+	n = (unsigned char)*p;
+	if (n > 0x7E || p[1 + n] != '\r')
+		return -1;
+
+	/* Initialize argv[0] to an empty string first. */
+	*p = 0;
+	argv[0] = p;
+
+	/*
+	 * Split the command line string into separate arguments.
+	 * TODO: handle double-quoting, backslashes, etc.
+	 */
+	pp = argv + 1;
+	do
+	{
+		do
+			c = *++p;
+		while (c == ' ' || c == '\t');
+
+		if (c != '\r')
+		{
+			*pp++ = p;
+			do
+				c = *++p;
+			while (c != ' ' && c != '\t' && c != '\r');
+			*p = 0;
+		}
+	} while (c != '\r');
+
+	/* Wrap up argv[].  Compute argc.  Free up unneeded space. */
+	out->argc = pp - argv;
+	*pp++ = NULL;
+	if (brk(pp) != 0)
+		return -1;
+
+	/* Allocate space for envp[]. */
+	if ((envp = sbrk((n_env_vars + 1) * sizeof(char *))) == OUT_OF_MEMORY)
+		return -1;
+	out->envp = envp;
+
+	/*
+	 * Populate envp[].  The environment data is simply a series of ASCIIZ
+	 * strings, one after another, terminated by an empty string.
+	 */
+	pp = envp;
+	p = env_data;
+	while (*p)
+	{
+		*pp++ = p;
+		while (*++p);
+		++p;
+	}
+	*pp = NULL;
+
+	/*
+	 * If there is a program name (MS-DOS version is 3 or above), point
+	 * argv[0] to it.
+	 *
+	 * p points to the zero byte just before the count of strings (a
+	 * shortword) following the environment variables, so advance p by 3
+	 * bytes to get at the program name.
+	 */
+	if ((msdos_ver & 0x00ff) >= 3)
+	{
+		p += 3;
+		argv[0] = p;
+	}
+
+	/* We are done. */
+	return 0;
+}

From aaf3ef695b12a88ab99986749dc2cf3672d6994e Mon Sep 17 00:00:00 2001
From: Tee-Kiah Chia <tkchia@users.noreply.github.com>
Date: Wed, 24 Mar 2021 14:30:18 +0000
Subject: [PATCH 2/8] plat/msdos86: implement close( ) function & proper errno
 setting

---
 plat/msdos86/libsys/close.s        | 23 +++++++++++++++
 plat/msdos86/libsys/errno.s        | 28 +++++++++++++++++++
 plat/msdos86/libsys/sys_seterrno.c | 45 ++++++++++++++++++++++++++++++
 plat/msdos86/libsys/sys_xret.s     | 35 +++++++++++++++++++++++
 4 files changed, 131 insertions(+)
 create mode 100644 plat/msdos86/libsys/close.s
 create mode 100644 plat/msdos86/libsys/errno.s
 create mode 100644 plat/msdos86/libsys/sys_seterrno.c
 create mode 100644 plat/msdos86/libsys/sys_xret.s

diff --git a/plat/msdos86/libsys/close.s b/plat/msdos86/libsys/close.s
new file mode 100644
index 000000000..b8c2f8a15
--- /dev/null
+++ b/plat/msdos86/libsys/close.s
@@ -0,0 +1,23 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Close a file.
+
+.define _close
+_close:
+	mov bx, sp
+	mov bx, 2(bx)
+	movb ah, 0x3E
+	int 0x21
+	jmp .sys_zret
diff --git a/plat/msdos86/libsys/errno.s b/plat/msdos86/libsys/errno.s
new file mode 100644
index 000000000..9858d2640
--- /dev/null
+++ b/plat/msdos86/libsys/errno.s
@@ -0,0 +1,28 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+#define D(e) .define e; e
+
+.sect .data
+
+! Define various ACK error numbers. Note that these are *not* ANSI C
+! errnos, and are used for different purposes.
+
+D(ERANGE)         = 1
+D(ESET)           = 2
+D(EIDIVZ)         = 6
+D(EHEAP)          = 17
+D(EILLINS)        = 18
+D(EODDZ)          = 19
+D(ECASE)          = 20
+D(EBADMON)        = 25
+
diff --git a/plat/msdos86/libsys/sys_seterrno.c b/plat/msdos86/libsys/sys_seterrno.c
new file mode 100644
index 000000000..779e600f5
--- /dev/null
+++ b/plat/msdos86/libsys/sys_seterrno.c
@@ -0,0 +1,45 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <errno.h>
+
+static const signed char err_map[] =
+	{
+		0,			/* 0x00 no error */
+		EINVAL,			/* 0x01 function number invalid */
+		ENOENT,			/* 0x02 file not found */
+		ENOENT,			/* 0x03 path not found */
+		EMFILE,			/* 0x04 too many open files */
+		EACCES,			/* 0x05 access denied */
+		EBADF,			/* 0x06 invalid handle */
+		EFAULT,			/* 0x07 mem. control block destroyed */
+		ENOMEM,			/* 0x08 insufficient memory */
+		EFAULT,			/* 0x09 memory block address invalid */
+		E2BIG,			/* 0x0A environment invalid */
+		ENOEXEC,		/* 0x0B format invalid */
+		EINVAL,			/* 0x0C access code invalid */
+		EINVAL,			/* 0x0D data invalid */
+		ENOEXEC,		/* 0x0E (?) fixup overflow */
+		ENODEV,			/* 0x0F invalid drive */
+		EBUSY,			/* 0x10 attempt to remove curr. dir. */
+		EXDEV,			/* 0x11 not same device */
+		ENOENT,			/* 0x12 no more files */
+		EIO,			/* 0x13 disk write-protected */
+		EIO,			/* 0x14 unknown unit */
+		ENXIO,			/* 0x15 drive not ready */
+	};
+
+/*
+ * Map an MS-DOS 2+ system error code to an `errno' value and store that in
+ * `errno'.  Return -1.
+ */
+int _sys_seterrno(unsigned dos_err)
+{
+	if (dos_err < sizeof(err_map) / sizeof(err_map[0]))
+		errno = err_map[dos_err];
+	else
+		errno = EIO;
+	return -1;
+}
diff --git a/plat/msdos86/libsys/sys_xret.s b/plat/msdos86/libsys/sys_xret.s
new file mode 100644
index 000000000..a5b65116a
--- /dev/null
+++ b/plat/msdos86/libsys/sys_xret.s
@@ -0,0 +1,35 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! .sys_zret: if the carry flag is set, then set `errno' from the DOS error
+! code in ax, and return -1.  If the carry flag is clear, just return zero.
+!
+! .sys_axret: if the carry flag is set, then set `errno' from the DOS error
+! code in ax, and return -1.  If the carry flag is clear, just return ax as
+! a return value.
+
+.extern .sys_zret
+.extern .sys_axret
+.sys_zret:
+	jc error
+	xor ax, ax
+no_error:
+	ret
+.sys_axret:
+	jnc no_error
+error:
+	push ax
+	call __sys_seterrno
+	pop cx
+	ret

From 2dfddf3fa8fce4172559858f38c77d577118bfaa Mon Sep 17 00:00:00 2001
From: Tee-Kiah Chia <tkchia@users.noreply.github.com>
Date: Sat, 27 Mar 2021 06:59:07 +0000
Subject: [PATCH 3/8] libcc.ansi: add support for O_TEXT, O_BINARY file status
 flags

---
 lang/cem/libcc.ansi/headers/ack/config.h  |  4 ++++
 lang/cem/libcc.ansi/headers/ack/emufile.h |  1 +
 lang/cem/libcc.ansi/headers/unistd.h      |  4 ++++
 lang/cem/libcc.ansi/sys/stdio/fdopen.c    | 18 ++++++++++++++++++
 lang/cem/libcc.ansi/sys/stdio/fopen.c     | 11 +++++++++--
 lang/cem/libcc.ansi/sys/stdio/freopen.c   | 10 +++++++++-
 6 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/lang/cem/libcc.ansi/headers/ack/config.h b/lang/cem/libcc.ansi/headers/ack/config.h
index 41e9bc3b6..cf8f5d835 100644
--- a/lang/cem/libcc.ansi/headers/ack/config.h
+++ b/lang/cem/libcc.ansi/headers/ack/config.h
@@ -15,6 +15,10 @@
 #define ACKCONF_WANT_STANDARD_O 1
 #endif
 
+#ifndef ACKCONF_WANT_O_TEXT_O_BINARY
+#define ACKCONF_WANT_O_TEXT_O_BINARY 0
+#endif
+
 #ifndef ACKCONF_WANT_STANDARD_SIGNALS
 #define ACKCONF_WANT_STANDARD_SIGNALS 1
 #endif
diff --git a/lang/cem/libcc.ansi/headers/ack/emufile.h b/lang/cem/libcc.ansi/headers/ack/emufile.h
index 06a1ffcec..158ec58a8 100644
--- a/lang/cem/libcc.ansi/headers/ack/emufile.h
+++ b/lang/cem/libcc.ansi/headers/ack/emufile.h
@@ -24,6 +24,7 @@ struct FILE {
 #define	_IOREADING	0x080
 #define _IOWRITING	0x100
 #define	_IOAPPEND	0x200
+#define _IOBINARY	0x400
 
 #if !defined BUFSIZ
 #define	BUFSIZ      1024
diff --git a/lang/cem/libcc.ansi/headers/unistd.h b/lang/cem/libcc.ansi/headers/unistd.h
index bab5ada71..a316132d2 100644
--- a/lang/cem/libcc.ansi/headers/unistd.h
+++ b/lang/cem/libcc.ansi/headers/unistd.h
@@ -24,6 +24,10 @@
         O_WRONLY = 1,
         O_RDWR = 2,
         
+    #if ACKCONF_WANT_O_TEXT_O_BINARY
+        O_TEXT = 010000,
+        O_BINARY = 020000,
+    #endif
         O_CREAT = 0100,
         O_TRUNC = 01000,
         O_APPEND = 02000,
diff --git a/lang/cem/libcc.ansi/sys/stdio/fdopen.c b/lang/cem/libcc.ansi/sys/stdio/fdopen.c
index aff7d248e..58fcecfcd 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fdopen.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fdopen.c
@@ -5,6 +5,10 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#if ACKCONF_WANT_O_TEXT_O_BINARY
+    #include <unistd.h>
+    #include <fcntl.h>
+#endif
 
 #if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
@@ -38,6 +42,9 @@ FILE* fdopen(int fd, const char* mode)
 		switch (*mode++)
 		{
 			case 'b':
+#if ACKCONF_WANT_O_TEXT_O_BINARY
+				flags |= _IOBINARY;
+#endif
 				continue;
 			case '+':
 				flags |= _IOREAD | _IOWRITE;
@@ -57,6 +64,17 @@ FILE* fdopen(int fd, const char* mode)
 	if ((flags & _IOREAD) && (flags & _IOWRITE))
 		flags &= ~(_IOREADING | _IOWRITING);
 
+#if ACKCONF_WANT_O_TEXT_O_BINARY
+	{
+		/*
+		 * FIXME: this assumes that any platform that has O_TEXT and
+		 * O_BINARY will also have a _setmode() function.
+		 */
+		extern int _setmode(int, int);
+		_setmode(fd, (flags & _IOBINARY) ? O_BINARY : O_TEXT);
+	}
+#endif
+
 	stream->_count = 0;
 	stream->_fd = fd;
 	stream->_flags = flags;
diff --git a/lang/cem/libcc.ansi/sys/stdio/fopen.c b/lang/cem/libcc.ansi/sys/stdio/fopen.c
index f2189ee8f..cfea44154 100644
--- a/lang/cem/libcc.ansi/sys/stdio/fopen.c
+++ b/lang/cem/libcc.ansi/sys/stdio/fopen.c
@@ -7,7 +7,6 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <fcntl.h>
-#include <unistd.h>
 
 #if ACKCONF_WANT_STDIO && ACKCONF_WANT_EMULATED_FILE
 
@@ -68,6 +67,9 @@ FILE* fopen(const char* name, const char* mode)
 		switch (*mode++)
 		{
 			case 'b':
+#if ACKCONF_WANT_O_TEXT_O_BINARY
+				flags |= _IOBINARY;
+#endif
 				continue;
 			case '+':
 				rwmode = O_RDWR;
@@ -80,6 +82,7 @@ FILE* fopen(const char* name, const char* mode)
 		break;
 	}
 
+#if !ACKCONF_WANT_O_TEXT_O_BINARY
 	/* Perform a creat() when the file should be truncated or when
 	 * the file is opened for writing and the open() failed.
 	 */
@@ -87,12 +90,16 @@ FILE* fopen(const char* name, const char* mode)
 	    || (((fd = open(name, rwmode)) < 0)
 	           && (rwflags & O_CREAT)))
 	{
-		if (((fd = creat(name, PMODE)) > 0) && flags | _IOREAD)
+		if (((fd = creat(name, PMODE)) >= 0) && (flags & _IOREAD))
 		{
 			(void)close(fd);
 			fd = open(name, rwmode);
 		}
 	}
+#else
+	rwflags |= (flags & _IOBINARY) ? O_BINARY : O_TEXT;
+	fd = open(name, rwmode | rwflags, PMODE);
+#endif
 
 	if (fd < 0)
 		return (FILE*)NULL;
diff --git a/lang/cem/libcc.ansi/sys/stdio/freopen.c b/lang/cem/libcc.ansi/sys/stdio/freopen.c
index 846208420..1ae5befe0 100644
--- a/lang/cem/libcc.ansi/sys/stdio/freopen.c
+++ b/lang/cem/libcc.ansi/sys/stdio/freopen.c
@@ -50,6 +50,9 @@ FILE* freopen(const char* name, const char* mode, FILE* stream)
 		switch (*mode++)
 		{
 			case 'b':
+#if ACKCONF_WANT_O_TEXT_O_BINARY
+				flags |= _IOBINARY;
+#endif
 				continue;
 			case '+':
 				rwmode = O_RDWR;
@@ -62,16 +65,21 @@ FILE* freopen(const char* name, const char* mode, FILE* stream)
 		break;
 	}
 
+#if !ACKCONF_WANT_O_TEXT_O_BINARY
 	if ((rwflags & O_TRUNC)
 	    || (((fd = open(name, rwmode)) < 0)
 	           && (rwflags & O_CREAT)))
 	{
-		if (((fd = creat(name, PMODE)) < 0) && flags | _IOREAD)
+		if (((fd = creat(name, PMODE)) >= 0) && (flags & _IOREAD))
 		{
 			(void)close(fd);
 			fd = open(name, rwmode);
 		}
 	}
+#else
+	rwflags |= (flags & _IOBINARY) ? O_BINARY : O_TEXT;
+	fd = open(name, rwmode | rwflags, PMODE);
+#endif
 
 	if (fd < 0)
 	{

From 0d2b55cd295930b3b77f326c7237ce11d9ceb06c Mon Sep 17 00:00:00 2001
From: Tee-Kiah Chia <tkchia@users.noreply.github.com>
Date: Sat, 27 Mar 2021 19:30:38 +0000
Subject: [PATCH 4/8] plat/msdos86: add isatty( ), _setmode( ), read( ), write(
 )

---
 plat/msdos86/descr                 |  2 +
 plat/msdos86/include/ack/plat.h    | 12 +++++
 plat/msdos86/include/build.lua     | 24 ++++++++++
 plat/msdos86/include/sys/types.h   |  9 ++++
 plat/msdos86/libsys/_hol0.s        | 19 ++++++++
 plat/msdos86/libsys/brk.c          | 59 +++++++++++++++++++++++
 plat/msdos86/libsys/build.lua      | 15 ++++++
 plat/msdos86/libsys/creat.c        | 14 ++++++
 plat/msdos86/libsys/isatty.s       | 37 ++++++++++++++
 plat/msdos86/libsys/libsys.h       | 53 ++++++++++++++++++++
 plat/msdos86/libsys/read.c         | 77 ++++++++++++++++++++++++++++++
 plat/msdos86/libsys/setmode.c      | 23 +++++++++
 plat/msdos86/libsys/sys_fdmodes.c  | 13 +++++
 plat/msdos86/libsys/sys_getmode.c  | 27 +++++++++++
 plat/msdos86/libsys/sys_initmain.c |  3 +-
 plat/msdos86/libsys/sys_iseof.c    | 27 +++++++++++
 plat/msdos86/libsys/sys_isopen.s   | 26 ++++++++++
 plat/msdos86/libsys/sys_isreadyr.s | 28 +++++++++++
 plat/msdos86/libsys/sys_rawrw.s    | 33 +++++++++++++
 plat/msdos86/libsys/sys_seteof.c   | 42 ++++++++++++++++
 plat/msdos86/libsys/sys_setmode.c  | 55 +++++++++++++++++++++
 plat/msdos86/libsys/write.c        | 61 +++++++++++++++++++++++
 22 files changed, 657 insertions(+), 2 deletions(-)
 create mode 100644 plat/msdos86/include/ack/plat.h
 create mode 100644 plat/msdos86/include/build.lua
 create mode 100644 plat/msdos86/include/sys/types.h
 create mode 100644 plat/msdos86/libsys/_hol0.s
 create mode 100644 plat/msdos86/libsys/brk.c
 create mode 100644 plat/msdos86/libsys/build.lua
 create mode 100644 plat/msdos86/libsys/creat.c
 create mode 100644 plat/msdos86/libsys/isatty.s
 create mode 100644 plat/msdos86/libsys/libsys.h
 create mode 100644 plat/msdos86/libsys/read.c
 create mode 100644 plat/msdos86/libsys/setmode.c
 create mode 100644 plat/msdos86/libsys/sys_fdmodes.c
 create mode 100644 plat/msdos86/libsys/sys_getmode.c
 create mode 100644 plat/msdos86/libsys/sys_iseof.c
 create mode 100644 plat/msdos86/libsys/sys_isopen.s
 create mode 100644 plat/msdos86/libsys/sys_isreadyr.s
 create mode 100644 plat/msdos86/libsys/sys_rawrw.s
 create mode 100644 plat/msdos86/libsys/sys_seteof.c
 create mode 100644 plat/msdos86/libsys/sys_setmode.c
 create mode 100644 plat/msdos86/libsys/write.c

diff --git a/plat/msdos86/descr b/plat/msdos86/descr
index 97c05751b..333bb671b 100644
--- a/plat/msdos86/descr
+++ b/plat/msdos86/descr
@@ -73,6 +73,8 @@ name led
 		{FLOATS?} \
 		(.e:{TAIL}={PLATFORMDIR}/libem.a \
 		           {PLATFORMDIR}/libsys.a \
+		           {PLATFORMDIR}/libc.a \
+		           {PLATFORMDIR}/libem.a \
 		           {PLATFORMDIR}/libend.a)
 	linker
 end
diff --git a/plat/msdos86/include/ack/plat.h b/plat/msdos86/include/ack/plat.h
new file mode 100644
index 000000000..a1e942cdd
--- /dev/null
+++ b/plat/msdos86/include/ack/plat.h
@@ -0,0 +1,12 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#ifndef _ACK_PLAT_H
+#define _ACK_PLAT_H
+
+#define ACKCONF_WANT_O_TEXT_O_BINARY 1
+#define ACKCONF_WANT_EMULATED_TIME 0
+
+#endif
diff --git a/plat/msdos86/include/build.lua b/plat/msdos86/include/build.lua
new file mode 100644
index 000000000..6ae480041
--- /dev/null
+++ b/plat/msdos86/include/build.lua
@@ -0,0 +1,24 @@
+include("plat/build.lua")
+
+headermap = {}
+packagemap = {}
+
+local function addheader(h)
+	headermap[h] = "./"..h
+	packagemap["$(PLATIND)/msdos86/include/"..h] = "./"..h
+end
+
+addheader("ack/plat.h")
+addheader("sys/types.h")
+
+acklibrary {
+	name = "headers",
+	hdrs = headermap
+}
+
+installable {
+	name = "pkg",
+	map = packagemap
+}
+
+
diff --git a/plat/msdos86/include/sys/types.h b/plat/msdos86/include/sys/types.h
new file mode 100644
index 000000000..6a0c3d3db
--- /dev/null
+++ b/plat/msdos86/include/sys/types.h
@@ -0,0 +1,9 @@
+#ifndef _SYS_TYPES_H
+#define _SYS_TYPES_H
+
+typedef int pid_t;
+typedef int mode_t;
+typedef long time_t;
+typedef long suseconds_t;
+
+#endif
diff --git a/plat/msdos86/libsys/_hol0.s b/plat/msdos86/libsys/_hol0.s
new file mode 100644
index 000000000..f01566fe8
--- /dev/null
+++ b/plat/msdos86/libsys/_hol0.s
@@ -0,0 +1,19 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .bss
+
+! This data block is used to store information about the current line number
+! and file.
+
+.define hol0
+.comm hol0, 8
diff --git a/plat/msdos86/libsys/brk.c b/plat/msdos86/libsys/brk.c
new file mode 100644
index 000000000..ab333e550
--- /dev/null
+++ b/plat/msdos86/libsys/brk.c
@@ -0,0 +1,59 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include "libsys.h"
+
+#define STACK_BUFFER 128 /* number of bytes to leave for stack */
+
+extern char _end[1];
+static char* current = _end;
+
+int brk(void* newend)
+{
+	/* This variable is used to figure out the current stack pointer,
+	 * by taking its address. */
+	char dummy;
+	char* p = newend;
+	
+	if ((p > (&dummy - STACK_BUFFER)) ||
+	    (p < _end))	
+	{
+		errno = ENOMEM;
+		return -1;
+	}
+		
+	current = p;
+	return 0;
+}
+
+void* sbrk(int increment)
+{
+	char* old;
+	char* new;
+
+	if (increment == 0)
+		return current;
+		
+	old = current;
+
+	new = old + increment;
+
+	if ((increment > 0) && (new <= old))
+		goto out_of_memory;
+	else if ((increment < 0) && (new >= old))
+		goto out_of_memory;
+
+	if (brk(new) < 0)
+		goto out_of_memory;
+		
+	return old;
+
+out_of_memory:
+	errno = ENOMEM;
+	return OUT_OF_MEMORY;
+}
diff --git a/plat/msdos86/libsys/build.lua b/plat/msdos86/libsys/build.lua
new file mode 100644
index 000000000..dd357082a
--- /dev/null
+++ b/plat/msdos86/libsys/build.lua
@@ -0,0 +1,15 @@
+acklibrary {
+    name = "lib",
+    srcs = {
+        "./*.c",
+        "./*.s",
+    },
+	deps = {
+		"lang/cem/libcc.ansi/headers+headers",
+		"plat/msdos86/include+headers",
+	},
+    vars = {
+        plat = "msdos86"
+    }
+}
+
diff --git a/plat/msdos86/libsys/creat.c b/plat/msdos86/libsys/creat.c
new file mode 100644
index 000000000..8f18317c5
--- /dev/null
+++ b/plat/msdos86/libsys/creat.c
@@ -0,0 +1,14 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include "libsys.h"
+
+int creat(const char* path, int mode)
+{
+	return open(path, O_CREAT|O_WRONLY|O_TRUNC, mode);
+}
diff --git a/plat/msdos86/libsys/isatty.s b/plat/msdos86/libsys/isatty.s
new file mode 100644
index 000000000..bd2e195e6
--- /dev/null
+++ b/plat/msdos86/libsys/isatty.s
@@ -0,0 +1,37 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Say whether a given file descriptor number refers to a terminal.
+
+.define _isatty
+_isatty:
+	mov bx, sp
+	mov bx, 2(bx)
+	mov ax, 0x4400
+	int 0x21
+	jc error
+	testb dl, dl
+	jz not_tty
+	mov ax, 1
+	ret
+not_tty:
+	mov (_errno), 25		! ENOTTY
+not_tty_2:
+	xor ax, ax
+	ret
+error:
+	push ax
+	call __sys_seterrno
+	pop cx
+	jmp not_tty_2
diff --git a/plat/msdos86/libsys/libsys.h b/plat/msdos86/libsys/libsys.h
new file mode 100644
index 000000000..ddba5cda6
--- /dev/null
+++ b/plat/msdos86/libsys/libsys.h
@@ -0,0 +1,53 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#ifndef LIBSYS_H
+#define LIBSYS_H
+
+#include <limits.h>
+#include <stdint.h>
+#include <sys/types.h>
+
+#define OUT_OF_MEMORY ((void *)-1)	/* sbrk returns this on failure */
+
+/*
+ * Data structure for remembering whether each file descriptor is open in
+ * text mode (O_TEXT) or binary mode (O_BINARY).
+ *
+ * Currently this is just a simple linked list, where each linked list node
+ * records the modes for 16 file descriptors, in bit vector form (0: text,
+ * 1: binary).  In addition, each node also remembers, for each of its file
+ * descriptors,  whether an end-of-file (^Z) character was encountered when
+ * reading from it in text mode.
+ *
+ * List nodes are allocated using sbrk() and never freed.
+ *
+ * This scheme should be fast and light enough, as the number of open file
+ * descriptors is expected to be small.
+ *
+ * FIXME: the code for updating this structure is not exactly thread-safe.
+ */
+typedef uint16_t _fdvec_t;
+
+struct _fdmodes {
+	struct _fdmodes *next;
+	int begfd;
+	_fdvec_t modevec, eofvec;
+};
+
+extern struct _fdmodes _sys_fdmodes;
+
+#define _FDVECMASK (sizeof(_fdvec_t) * CHAR_BIT - 1)
+
+extern int _sys_getmode(int);
+extern int _sys_setmode(int, int);
+extern int _sys_iseof(int);
+extern int _sys_seteof(int, int);
+extern ssize_t _sys_rawread(int, char *, size_t);
+extern ssize_t _sys_rawwrite(int, const char *, size_t);
+extern int _sys_isopen(int);
+extern int _sys_isreadyr(int);
+
+#endif
diff --git a/plat/msdos86/libsys/read.c b/plat/msdos86/libsys/read.c
new file mode 100644
index 000000000..71711832e
--- /dev/null
+++ b/plat/msdos86/libsys/read.c
@@ -0,0 +1,77 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include "libsys.h"
+
+ssize_t read(int fd, void* buffer, size_t count)
+{
+	char *p, *q;
+	ssize_t r, tot;
+	size_t left;
+	int eof = 0;
+
+	if (!count || _sys_getmode(fd) == O_BINARY)
+		return _sys_rawread(fd, buffer, count);
+
+	if (_sys_iseof(fd))
+		return 0;
+
+	/*
+	 * If the file descriptor is an O_TEXT fd, read from it, and then
+	 * remove CRs from the input.  After removing CRs, if the buffer is
+	 * not filled and the fd still has bytes left to read, then keep
+	 * reading, and keep removing CRs.
+	 *
+	 * Also handle end-of-file indicators (^Z).  If we see one, move the
+	 * file pointer to just before the ^Z.  Also set an internal flag
+	 * for the fd so that we do not try to read any further (until e.g. 
+	 * a seek happens).
+	 */
+	p = buffer;
+	tot = 0;
+
+	do
+	{
+		r = _sys_rawread(fd, p, count - (p - (char *)buffer));
+		if (r <= 0)
+			return tot;
+
+		q = memchr(p, 0x1a, (size_t)r);
+		if (q)
+		{
+			_sys_rawlseek(fd, (off_t)(q - p) - r, SEEK_CUR);
+			r = q - p;
+			eof = 1;
+			_sys_seteof(fd, 1);
+		}
+
+		q = memchr(p, '\r', (size_t)r);
+		if (!q)
+			return tot + r;
+
+		tot += q - p;
+		left = r - (q + 1 - p);
+		p = q;
+		++q;
+
+		while (left)
+		{
+			char c = *q++;
+			if (c != '\r')
+			{
+				*p++ = c;
+				++tot;
+			}
+			--left;
+		}
+	} while (tot < count && !eof && _sys_isreadyr(fd));
+
+	return tot;
+}
diff --git a/plat/msdos86/libsys/setmode.c b/plat/msdos86/libsys/setmode.c
new file mode 100644
index 000000000..ac086d397
--- /dev/null
+++ b/plat/msdos86/libsys/setmode.c
@@ -0,0 +1,23 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include "libsys.h"
+
+int _setmode(int fd, int mode)
+{
+	if (mode != O_TEXT && mode != O_BINARY)
+	{
+		errno = EINVAL;
+		return -1;
+	}
+	if (!_sys_isopen(fd))
+	{
+		errno = EBADF;
+		return -1;
+	}
+	return _sys_setmode(fd, mode);
+}
diff --git a/plat/msdos86/libsys/sys_fdmodes.c b/plat/msdos86/libsys/sys_fdmodes.c
new file mode 100644
index 000000000..c37b5bc7e
--- /dev/null
+++ b/plat/msdos86/libsys/sys_fdmodes.c
@@ -0,0 +1,13 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <stdlib.h>
+#include "libsys.h"
+
+/*
+ * By default, consider all file descriptors, including those for stdin (0),
+ * stdout (1), and stderr (2), as being open in text mode.
+ */
+struct _fdmodes _sys_fdmodes = { NULL, 0, 0 };
diff --git a/plat/msdos86/libsys/sys_getmode.c b/plat/msdos86/libsys/sys_getmode.c
new file mode 100644
index 000000000..4ae0aba2d
--- /dev/null
+++ b/plat/msdos86/libsys/sys_getmode.c
@@ -0,0 +1,27 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <fcntl.h>
+#include "libsys.h"
+
+/*
+ * Say whether a particular fd is currently open in text or binary mode.
+ * Assume that the fd is valid.  Return O_TEXT or O_BINARY.
+ */
+int _sys_getmode(int fd)
+{
+	int reqbegfd = fd & ~_FDVECMASK;
+	struct _fdmodes *p = &_sys_fdmodes;
+	_fdvec_t mask;
+
+	while (p->begfd != reqbegfd)
+	{
+		p = p->next;
+		if (!p)
+			return O_TEXT;
+	}
+	mask = (_fdvec_t)1 << (fd & _FDVECMASK);
+	return (p->modevec & mask) ? O_BINARY : O_TEXT;
+}
diff --git a/plat/msdos86/libsys/sys_initmain.c b/plat/msdos86/libsys/sys_initmain.c
index 11b5a1fb4..5530a0510 100644
--- a/plat/msdos86/libsys/sys_initmain.c
+++ b/plat/msdos86/libsys/sys_initmain.c
@@ -6,8 +6,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
-
-#define	OUT_OF_MEMORY (void*)(-1)	/* sbrk returns this on failure */
+#include "libsys.h"
 
 struct for_main {
 	int argc;
diff --git a/plat/msdos86/libsys/sys_iseof.c b/plat/msdos86/libsys/sys_iseof.c
new file mode 100644
index 000000000..ab9f6c994
--- /dev/null
+++ b/plat/msdos86/libsys/sys_iseof.c
@@ -0,0 +1,27 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <fcntl.h>
+#include "libsys.h"
+
+/*
+ * Say whether a particular fd is currently open in text mode and has just
+ * hit an MS-DOS end-of-file character (^Z).
+ */
+int _sys_iseof(int fd)
+{
+	int reqbegfd = fd & ~_FDVECMASK;
+	struct _fdmodes *p = &_sys_fdmodes;
+	_fdvec_t mask;
+
+	while (p->begfd != reqbegfd)
+	{
+		p = p->next;
+		if (!p)
+			return 0;
+	}
+	mask = (_fdvec_t)1 << (fd & _FDVECMASK);
+	return p->eofvec & mask;
+}
diff --git a/plat/msdos86/libsys/sys_isopen.s b/plat/msdos86/libsys/sys_isopen.s
new file mode 100644
index 000000000..5ce49ed45
--- /dev/null
+++ b/plat/msdos86/libsys/sys_isopen.s
@@ -0,0 +1,26 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Say whether a given file descriptor number refers to a valid open file
+! descriptor.
+
+.define __sys_isopen
+__sys_isopen:
+	mov bx, sp
+	mov bx, 2(bx)
+	mov ax, 0x4400
+	int 0x21
+	sbb ax, ax
+	inc ax
+	ret
diff --git a/plat/msdos86/libsys/sys_isreadyr.s b/plat/msdos86/libsys/sys_isreadyr.s
new file mode 100644
index 000000000..b5d0800ee
--- /dev/null
+++ b/plat/msdos86/libsys/sys_isreadyr.s
@@ -0,0 +1,28 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Say whether a file descriptor is ready for input, i.e. reading from the
+! fd will immediately return something.
+
+.define __sys_isreadyr
+__sys_isreadyr:
+	mov bx, sp
+	mov ax, 0x4406
+	mov bx, 2(bx)
+	int 0x21
+	jnc ok
+	movb al, 0
+ok:
+	cbw
+	ret
diff --git a/plat/msdos86/libsys/sys_rawrw.s b/plat/msdos86/libsys/sys_rawrw.s
new file mode 100644
index 000000000..a306d6528
--- /dev/null
+++ b/plat/msdos86/libsys/sys_rawrw.s
@@ -0,0 +1,33 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Read/write bytes to/to a file descriptor.  These routines do not do any
+! translation between CRLF and LF line endings.
+!
+! Note that, for MS-DOS, a raw "write" request of zero bytes will truncate
+! (or extend) the file to the current file position.
+
+.define __sys_rawread
+__sys_rawread:
+	movb ah, 0x3f
+	.data1 0x3d			! eat up the next instruction
+.define __sys_rawwrite
+__sys_rawwrite:
+	movb ah, 0x40
+	mov bx, sp
+	mov dx, 4(bx)
+	mov cx, 6(bx)
+	mov bx, 2(bx)
+	int 0x21
+	jmp .sys_axret
diff --git a/plat/msdos86/libsys/sys_seteof.c b/plat/msdos86/libsys/sys_seteof.c
new file mode 100644
index 000000000..643e2167f
--- /dev/null
+++ b/plat/msdos86/libsys/sys_seteof.c
@@ -0,0 +1,42 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <fcntl.h>
+#include "libsys.h"
+
+/*
+ * Set or reset the "end-of-file encountered" indicator for a particular fd.
+ * Assume that the fd is valid, and is being read from in text mode.
+ */
+int _sys_seteof(int fd, int eof)
+{
+	int reqbegfd = fd & ~_FDVECMASK;
+	struct _fdmodes *p = &_sys_fdmodes;
+	_fdvec_t mask;
+
+	while (p->begfd != reqbegfd)
+	{
+		p = p->next;
+		if (!p)
+		{
+			if (!eof)
+				return 0;
+			if ((p = sbrk(sizeof(struct _fdmodes)))
+			    == OUT_OF_MEMORY)
+				return -1;
+			p->next = _sys_fdmodes.next;
+			p->begfd = reqbegfd;
+			p->modevec = p->eofvec = 0;
+			_sys_fdmodes.next = p;
+			break;
+		}
+	}
+	mask = (_fdvec_t)1 << (fd & _FDVECMASK);
+	if (eof)
+		p->eofvec |= mask;
+	else
+		p->eofvec &= ~mask;
+	return 0;
+}
diff --git a/plat/msdos86/libsys/sys_setmode.c b/plat/msdos86/libsys/sys_setmode.c
new file mode 100644
index 000000000..6191e9027
--- /dev/null
+++ b/plat/msdos86/libsys/sys_setmode.c
@@ -0,0 +1,55 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <fcntl.h>
+#include "libsys.h"
+
+/*
+ * Set text/binary mode for a particular fd.  Assume that the fd is valid,
+ * and that the mode is either O_TEXT or O_BINARY.
+ *
+ * Return the previous mode (either O_TEXT or O_BINARY) on success, -1 (with
+ * errno set) on error.
+ */
+int _sys_setmode(int fd, int mode)
+{
+	int reqbegfd = fd & ~_FDVECMASK;
+	struct _fdmodes *p = &_sys_fdmodes;
+	_fdvec_t mask;
+
+	while (p->begfd != reqbegfd)
+	{
+		p = p->next;
+		if (!p)
+		{
+			if (mode == O_TEXT)
+				return O_TEXT;
+			if ((p = sbrk(sizeof(struct _fdmodes)))
+			    == OUT_OF_MEMORY)
+				return -1;
+			p->next = _sys_fdmodes.next;
+			p->begfd = reqbegfd;
+			p->modevec = p->eofvec = 0;
+			_sys_fdmodes.next = p;
+			break;
+		}
+	}
+	mask = (_fdvec_t)1 << (fd & _FDVECMASK);
+	if (mode == O_BINARY)
+	{
+		if (p->modevec & mask)
+			return O_BINARY;
+		p->modevec |= mask;
+		p->eofvec &= ~mask;
+		return O_TEXT;
+	}
+	else
+	{
+		if (!(p->modevec & mask))
+			return O_TEXT;
+		p->modevec &= ~mask;
+		return O_BINARY;
+	}
+}
diff --git a/plat/msdos86/libsys/write.c b/plat/msdos86/libsys/write.c
new file mode 100644
index 000000000..fc744b256
--- /dev/null
+++ b/plat/msdos86/libsys/write.c
@@ -0,0 +1,61 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include "libsys.h"
+
+ssize_t write(int fd, void* buffer, size_t count)
+{
+	static const char crlf[2] = "\r\n";
+	int i;
+	char *p, *q;
+	size_t left, n;
+	ssize_t r, tot;
+
+	if (!count)
+		return 0;
+
+	if (_sys_getmode(fd) == O_BINARY)
+		return _sys_rawwrite(fd, buffer, count);
+
+	/* If the file descriptor is an O_TEXT fd, translate LFs to CRLFs. */
+	p = buffer;
+	left = count;
+	tot = 0;
+	while (left)
+	{
+		q = memchr(p, '\n', left);
+		if (!q)
+			return _sys_rawwrite(fd, p, left);
+
+		n = q - p;
+		if (n)
+		{
+			r = _sys_rawwrite(fd, p, n);
+			if (r <= 0)
+				return tot ? tot : r;
+			tot += r;
+			p += r;
+			left -= r;
+			if (r != n)
+				break;
+		}
+
+		r = _sys_rawwrite(fd, crlf, sizeof crlf);
+		if (r != 2)
+		{
+			if (r > 0)
+				r = 0;
+			return tot ? tot : r;
+		}
+		++tot;
+		++p;
+		--left;
+	}
+	return tot;
+}

From 466cf20805a99dc4dbcbf8eb9f69ad2cd61b965c Mon Sep 17 00:00:00 2001
From: Tee-Kiah Chia <tkchia@users.noreply.github.com>
Date: Sun, 28 Mar 2021 12:09:52 +0000
Subject: [PATCH 5/8] plat/msdos86: add open( ), lseek( ), and getpid()

---
 plat/msdos86/include/sys/types.h   |   2 +-
 plat/msdos86/libsys/getpid.s       |  27 ++++++++
 plat/msdos86/libsys/libsys.h       |   5 ++
 plat/msdos86/libsys/lseek.c        |  26 ++++++++
 plat/msdos86/libsys/open.c         | 101 +++++++++++++++++++++++++++++
 plat/msdos86/libsys/sys_exists.s   |  25 +++++++
 plat/msdos86/libsys/sys_rawcreat.s |  24 +++++++
 plat/msdos86/libsys/sys_rawlseek.s |  26 ++++++++
 plat/msdos86/libsys/sys_rawopen.s  |  24 +++++++
 plat/msdos86/libsys/sys_seterrno.c |   4 +-
 plat/msdos86/libsys/sys_xret.s     |  12 +++-
 11 files changed, 270 insertions(+), 6 deletions(-)
 create mode 100644 plat/msdos86/libsys/getpid.s
 create mode 100644 plat/msdos86/libsys/lseek.c
 create mode 100644 plat/msdos86/libsys/open.c
 create mode 100644 plat/msdos86/libsys/sys_exists.s
 create mode 100644 plat/msdos86/libsys/sys_rawcreat.s
 create mode 100644 plat/msdos86/libsys/sys_rawlseek.s
 create mode 100644 plat/msdos86/libsys/sys_rawopen.s

diff --git a/plat/msdos86/include/sys/types.h b/plat/msdos86/include/sys/types.h
index 6a0c3d3db..005f48eb0 100644
--- a/plat/msdos86/include/sys/types.h
+++ b/plat/msdos86/include/sys/types.h
@@ -1,7 +1,7 @@
 #ifndef _SYS_TYPES_H
 #define _SYS_TYPES_H
 
-typedef int pid_t;
+typedef long pid_t;
 typedef int mode_t;
 typedef long time_t;
 typedef long suseconds_t;
diff --git a/plat/msdos86/libsys/getpid.s b/plat/msdos86/libsys/getpid.s
new file mode 100644
index 000000000..009c4f9f4
--- /dev/null
+++ b/plat/msdos86/libsys/getpid.s
@@ -0,0 +1,27 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Get the current process identifier.  For MS-DOS, use the Program Segment
+! Prefix (PSP) segment as the PID.
+!
+! (Note that pid_t is a 32-bit type.  This is to allow for PSP addresses
+! above 0x7FFF:0.)
+
+.define _getpid
+_getpid:
+	movb ah, 0x51
+	int 0x21
+	xchg bx, ax
+	xor dx, dx
+	ret
diff --git a/plat/msdos86/libsys/libsys.h b/plat/msdos86/libsys/libsys.h
index ddba5cda6..3488c332e 100644
--- a/plat/msdos86/libsys/libsys.h
+++ b/plat/msdos86/libsys/libsys.h
@@ -49,5 +49,10 @@ extern ssize_t _sys_rawread(int, char *, size_t);
 extern ssize_t _sys_rawwrite(int, const char *, size_t);
 extern int _sys_isopen(int);
 extern int _sys_isreadyr(int);
+extern int _sys_exists(const char *);
+extern int _sys_rawcreat(const char *, unsigned);
+extern int _sys_rawopen(const char *, int);
+extern off_t _sys_rawlseek(int, off_t, int);
+
 
 #endif
diff --git a/plat/msdos86/libsys/lseek.c b/plat/msdos86/libsys/lseek.c
new file mode 100644
index 000000000..db996a1dd
--- /dev/null
+++ b/plat/msdos86/libsys/lseek.c
@@ -0,0 +1,26 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include "libsys.h"
+
+off_t lseek(int fd, off_t offset, int whence)
+{
+	off_t newoff;
+
+	if (whence != SEEK_SET && whence != SEEK_CUR && whence != SEEK_END)
+	{
+		errno = EINVAL;
+		return -1L;
+	}
+
+	newoff = _sys_rawlseek(fd, offset, whence);
+	if (newoff != -1L)
+		_sys_seteof(fd, 0);
+
+	return newoff;
+}
diff --git a/plat/msdos86/libsys/open.c b/plat/msdos86/libsys/open.c
new file mode 100644
index 000000000..038ab004b
--- /dev/null
+++ b/plat/msdos86/libsys/open.c
@@ -0,0 +1,101 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+/*
+ * Derived from dos-open.c for newlib-ia16 which was written for the
+ * gcc-ia16 toolchain.
+ *
+ * Copyright (c) 2018 Bart Oldeman
+ * Copyright (c) 2019--2021 TK Chia
+ *
+ * The authors hereby grant permission to use, copy, modify, distribute,
+ * and license this software and its documentation for any purpose, provided
+ * that existing copyright notices are retained in all copies and that this
+ * notice is included verbatim in any distributions. No written agreement,
+ * license, or royalty fee is required for any of the authorized uses.
+ * Modifications to this software may be copyrighted by their authors
+ * and need not follow the licensing terms described here, provided that
+ * the new terms are clearly indicated on the first page of each file where
+ * they apply.
+ */
+
+#include <errno.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <unistd.h>
+#include "libsys.h"
+
+int open(const char* pathname, int flags, ...)
+{
+	int fd = -1, binmode;
+	off_t ret;
+
+	if ((flags & ~(O_ACCMODE | O_CREAT | O_TRUNC | O_APPEND
+		       | O_TEXT | O_BINARY)))
+	{
+		/* bail out if there are unknown flags */
+		errno = EINVAL;
+		return -1;
+	}
+
+	binmode = flags & (O_TEXT | O_BINARY);
+	if (binmode != O_TEXT && binmode != O_BINARY && binmode != 0)
+	{
+		/* bail out if both O_TEXT and O_BINARY are specified (!) */
+		errno = EINVAL;
+		return -1;
+	}
+
+	if ((flags & O_CREAT))
+	{
+		/* special but common case O_WRONLY | O_CREAT | O_TRUNC
+		 * should be handled by only calling _sys_rawcreat */
+		int fileexists = 0;
+		if (!(flags & O_TRUNC))
+			fileexists = _sys_exists(pathname);
+		if (!fileexists)
+		{
+			va_list ap;
+			mode_t mode;
+
+			va_start(ap, flags);
+			mode = va_arg(ap, mode_t);
+			va_end(ap);
+
+			fd = _sys_rawcreat(pathname, mode & 0200 ? 0 : 1);
+			if (fd != -1)
+			{
+				if ((flags & O_ACCMODE) == O_WRONLY)
+					return fd;
+				close(fd);
+				fd = -1;
+			}
+		}
+	}
+
+	/* try to open file with mode */
+	if (fd == -1)
+		fd = _sys_rawopen(pathname, flags & O_ACCMODE);
+	if (fd == -1)
+		return fd;
+	ret = 0;
+
+	/* handle O_TRUNC and O_APPEND */
+	if ((flags & O_TRUNC))
+		ret = _sys_rawwrite(fd, NULL, 0);
+	else if ((flags & O_APPEND))
+		ret = _sys_rawlseek(fd, 0L, SEEK_END);
+	if (ret == -1)
+	{
+		close(fd);
+		return -1;
+	}
+
+	/* handle O_TEXT and O_BINARY, and reset "end of file encountered" */
+	_sys_setmode(fd, binmode == O_BINARY ? O_BINARY : O_TEXT);
+	_sys_seteof(fd, 0);
+
+	return fd;
+}
diff --git a/plat/msdos86/libsys/sys_exists.s b/plat/msdos86/libsys/sys_exists.s
new file mode 100644
index 000000000..e282ef687
--- /dev/null
+++ b/plat/msdos86/libsys/sys_exists.s
@@ -0,0 +1,25 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Say whether a file exists with the given name.
+
+.define __sys_exists
+__sys_exists:
+	mov bx, sp
+	mov dx, 2(bx)
+	mov ax, 0x4300
+	int 0x21
+	sbb ax, ax
+	inc ax
+	ret
diff --git a/plat/msdos86/libsys/sys_rawcreat.s b/plat/msdos86/libsys/sys_rawcreat.s
new file mode 100644
index 000000000..67bc34e59
--- /dev/null
+++ b/plat/msdos86/libsys/sys_rawcreat.s
@@ -0,0 +1,24 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Create or truncate a file.
+
+.define __sys_rawcreat
+__sys_rawcreat:
+	movb ah, 0x3c
+	mov bx, sp
+	mov dx, 2(bx)
+	mov cx, 4(bx)
+	int 0x21
+	jmp .sys_axret
diff --git a/plat/msdos86/libsys/sys_rawlseek.s b/plat/msdos86/libsys/sys_rawlseek.s
new file mode 100644
index 000000000..992c4c655
--- /dev/null
+++ b/plat/msdos86/libsys/sys_rawlseek.s
@@ -0,0 +1,26 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Move the current file position for a file descriptor.
+
+.define __sys_rawlseek
+__sys_rawlseek:
+	movb ah, 0x42
+	mov bx, sp
+	mov dx, 4(bx)
+	mov cx, 6(bx)
+	movb al, 8(bx)
+	mov bx, 2(bx)
+	int 0x21
+	jmp .sys_dxaxret
diff --git a/plat/msdos86/libsys/sys_rawopen.s b/plat/msdos86/libsys/sys_rawopen.s
new file mode 100644
index 000000000..301e2fded
--- /dev/null
+++ b/plat/msdos86/libsys/sys_rawopen.s
@@ -0,0 +1,24 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Open an existing file.
+
+.define __sys_rawopen
+__sys_rawopen:
+	movb ah, 0x3d
+	mov bx, sp
+	mov dx, 2(bx)
+	movb al, 4(bx)
+	int 0x21
+	jmp .sys_axret
diff --git a/plat/msdos86/libsys/sys_seterrno.c b/plat/msdos86/libsys/sys_seterrno.c
index 779e600f5..b135aea33 100644
--- a/plat/msdos86/libsys/sys_seterrno.c
+++ b/plat/msdos86/libsys/sys_seterrno.c
@@ -33,9 +33,9 @@ static const signed char err_map[] =
 
 /*
  * Map an MS-DOS 2+ system error code to an `errno' value and store that in
- * `errno'.  Return -1.
+ * `errno'.  Return a longword -1.
  */
-int _sys_seterrno(unsigned dos_err)
+long _sys_seterrno(unsigned dos_err)
 {
 	if (dos_err < sizeof(err_map) / sizeof(err_map[0]))
 		errno = err_map[dos_err];
diff --git a/plat/msdos86/libsys/sys_xret.s b/plat/msdos86/libsys/sys_xret.s
index a5b65116a..57f407ef4 100644
--- a/plat/msdos86/libsys/sys_xret.s
+++ b/plat/msdos86/libsys/sys_xret.s
@@ -13,20 +13,26 @@
 .sect .text
 
 ! .sys_zret: if the carry flag is set, then set `errno' from the DOS error
-! code in ax, and return -1.  If the carry flag is clear, just return zero.
+! code in ax, and return a shortword -1.  If the carry flag is clear, just
+! return a shortword zero.
 !
 ! .sys_axret: if the carry flag is set, then set `errno' from the DOS error
-! code in ax, and return -1.  If the carry flag is clear, just return ax as
-! a return value.
+! code in ax, and return a shortword -1.  If the carry flag is clear, just
+! return ax as a return value.
+!
+! .sys_dxaxret: same as .sys_axret, but return a longword -1 or dx:ax as a
+! return value.
 
 .extern .sys_zret
 .extern .sys_axret
+.extern .sys_dxaxret
 .sys_zret:
 	jc error
 	xor ax, ax
 no_error:
 	ret
 .sys_axret:
+.sys_dxaxret:
 	jnc no_error
 error:
 	push ax

From f2c8828a4b034eefdeaffa5d1e1c3234d542e74d Mon Sep 17 00:00:00 2001
From: Tee-Kiah Chia <tkchia@users.noreply.github.com>
Date: Sun, 28 Mar 2021 12:28:57 +0000
Subject: [PATCH 6/8] plat/msdos86: copy stubs kill( ), signal( ), from
 plat/pc86

---
 plat/msdos86/libsys/kill.c   | 14 ++++++++++++++
 plat/msdos86/libsys/signal.c | 15 +++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 plat/msdos86/libsys/kill.c
 create mode 100644 plat/msdos86/libsys/signal.c

diff --git a/plat/msdos86/libsys/kill.c b/plat/msdos86/libsys/kill.c
new file mode 100644
index 000000000..4a179c47c
--- /dev/null
+++ b/plat/msdos86/libsys/kill.c
@@ -0,0 +1,14 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+
+int kill(pid_t pid, int sig)
+{
+	errno = EINVAL;
+	return -1;
+}
diff --git a/plat/msdos86/libsys/signal.c b/plat/msdos86/libsys/signal.c
new file mode 100644
index 000000000..a87b9ced2
--- /dev/null
+++ b/plat/msdos86/libsys/signal.c
@@ -0,0 +1,15 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <signal.h>
+#include "libsys.h"
+
+sighandler_t signal(int signum, sighandler_t handler)
+{
+	return SIG_DFL;
+}

From a6c7ac2a280b895a7dfb29cda31510c757b50f77 Mon Sep 17 00:00:00 2001
From: Tee-Kiah Chia <tkchia@users.noreply.github.com>
Date: Mon, 29 Mar 2021 15:15:13 +0000
Subject: [PATCH 7/8] plat/msdos86: add gettimeofday( )

---
 plat/msdos86/include/ack/plat.h    |  1 -
 plat/msdos86/libsys/gettimeofday.c | 92 ++++++++++++++++++++++++++++++
 plat/msdos86/libsys/libsys.h       | 18 +++++-
 plat/msdos86/libsys/sys_getdate.s  | 25 ++++++++
 plat/msdos86/libsys/sys_gettime.s  | 25 ++++++++
 5 files changed, 159 insertions(+), 2 deletions(-)
 create mode 100644 plat/msdos86/libsys/gettimeofday.c
 create mode 100644 plat/msdos86/libsys/sys_getdate.s
 create mode 100644 plat/msdos86/libsys/sys_gettime.s

diff --git a/plat/msdos86/include/ack/plat.h b/plat/msdos86/include/ack/plat.h
index a1e942cdd..4343f1cf8 100644
--- a/plat/msdos86/include/ack/plat.h
+++ b/plat/msdos86/include/ack/plat.h
@@ -7,6 +7,5 @@
 #define _ACK_PLAT_H
 
 #define ACKCONF_WANT_O_TEXT_O_BINARY 1
-#define ACKCONF_WANT_EMULATED_TIME 0
 
 #endif
diff --git a/plat/msdos86/libsys/gettimeofday.c b/plat/msdos86/libsys/gettimeofday.c
new file mode 100644
index 000000000..5cea28f0f
--- /dev/null
+++ b/plat/msdos86/libsys/gettimeofday.c
@@ -0,0 +1,92 @@
+/* $Source$
+ * $State$
+ * $Revision$
+ */
+
+/*
+ * Derived from dos-gettimeofday.c for newlib-ia16 which was written for the
+ * gcc-ia16 toolchain.
+ *
+ * Copyright (c) 2017--2021 TK Chia
+ *
+ * The authors hereby grant permission to use, copy, modify, distribute,
+ * and license this software and its documentation for any purpose, provided
+ * that existing copyright notices are retained in all copies and that this
+ * notice is included verbatim in any distributions. No written agreement,
+ * license, or royalty fee is required for any of the authorized uses.
+ * Modifications to this software may be copyrighted by their authors
+ * and need not follow the licensing terms described here, provided that
+ * the new terms are clearly indicated on the first page of each file where
+ * they apply.
+ */
+
+#include <string.h>
+#include <unistd.h>
+#include <time.h>
+#include <stdbool.h>
+#include "libsys.h"
+
+extern long _timezone;
+extern int _daylight;
+
+int gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+	static volatile bool tzinited = false;
+	struct _dosdate dosdt, olddt;
+	struct _dostime dostm;
+	suseconds_t usec;
+	struct tm tm;
+	time_t tim;
+
+	if (!tzinited)
+	{
+		tzset();
+		tzinited = true;
+	}
+
+	memset(&tm, 0, sizeof tm);
+
+	_sys_getdate(&dosdt);
+	do
+	{
+		uint8_t hour;
+
+		_sys_gettime(&dostm);
+		tm.tm_hour = hour = dostm.hour;
+		tm.tm_min = dostm.minute;
+		tm.tm_sec = dostm.second;
+		usec = dostm.hsecond * 10000UL;
+
+		/* If the time is close to midnight, read the date again to
+		 * check for midnight crossover.  If crossover happens,
+		 * repeat until it stops. */
+		if (hour)
+			break;
+
+		olddt = dosdt;
+		_sys_getdate(&dosdt);
+	} while (dosdt.day != olddt.day);
+
+	tm.tm_year = dosdt.year - 1900;
+	tm.tm_mon = dosdt.month - 1;
+	tm.tm_mday = dosdt.day;
+	tm.tm_isdst = -1;
+
+	tim = mktime(&tm);
+	if (tim == -1)
+		return -1;
+
+	if (tv)
+	{
+		tv->tv_sec = tim;
+		tv->tv_usec = usec;
+	}
+
+	if (tz)
+	{
+		tz->tz_minuteswest = _timezone / 60;
+		tz->tz_dsttime = _daylight;
+	}
+
+	return 0;
+}
diff --git a/plat/msdos86/libsys/libsys.h b/plat/msdos86/libsys/libsys.h
index 3488c332e..e6aad45de 100644
--- a/plat/msdos86/libsys/libsys.h
+++ b/plat/msdos86/libsys/libsys.h
@@ -41,6 +41,21 @@ extern struct _fdmodes _sys_fdmodes;
 
 #define _FDVECMASK (sizeof(_fdvec_t) * CHAR_BIT - 1)
 
+/* Structures for getting MS-DOS's idea of the current date and time. */
+
+struct _dosdate {
+	uint8_t day;
+	uint8_t month;
+	uint16_t year;
+};
+
+struct _dostime {
+	uint8_t minute;
+	uint8_t hour;
+	uint8_t hsecond;
+	uint8_t second;
+};
+
 extern int _sys_getmode(int);
 extern int _sys_setmode(int, int);
 extern int _sys_iseof(int);
@@ -53,6 +68,7 @@ extern int _sys_exists(const char *);
 extern int _sys_rawcreat(const char *, unsigned);
 extern int _sys_rawopen(const char *, int);
 extern off_t _sys_rawlseek(int, off_t, int);
-
+extern void _sys_getdate(struct _dosdate *);
+extern void _sys_gettime(struct _dostime *);
 
 #endif
diff --git a/plat/msdos86/libsys/sys_getdate.s b/plat/msdos86/libsys/sys_getdate.s
new file mode 100644
index 000000000..41d69fc85
--- /dev/null
+++ b/plat/msdos86/libsys/sys_getdate.s
@@ -0,0 +1,25 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Get the current system date from MS-DOS.
+
+.define __sys_getdate
+__sys_getdate:
+	movb ah, 0x2a
+	int 0x21
+	mov bx, sp
+	mov bx, 2(bx)
+	mov (bx), dx
+	mov 2(bx), cx
+	ret
diff --git a/plat/msdos86/libsys/sys_gettime.s b/plat/msdos86/libsys/sys_gettime.s
new file mode 100644
index 000000000..d062fad8d
--- /dev/null
+++ b/plat/msdos86/libsys/sys_gettime.s
@@ -0,0 +1,25 @@
+#
+! $Source$
+! $State$
+! $Revision$
+
+! Declare segments (the order is important).
+
+.sect .text
+.sect .rom
+.sect .data
+.sect .bss
+
+.sect .text
+
+! Get the current system time from MS-DOS.
+
+.define __sys_gettime
+__sys_gettime:
+	movb ah, 0x2c
+	int 0x21
+	mov bx, sp
+	mov bx, 2(bx)
+	mov (bx), cx
+	mov 2(bx), dx
+	ret

From 85953022b5febac9ab5787032b2883af2e18960e Mon Sep 17 00:00:00 2001
From: Tee-Kiah Chia <tkchia@users.noreply.github.com>
Date: Thu, 1 Apr 2021 14:42:02 +0000
Subject: [PATCH 8/8] README: mention msdos86 target platform

---
 README | 1 +
 1 file changed, 1 insertion(+)

diff --git a/README b/README
index c27385337..53630e755 100644
--- a/README
+++ b/README
@@ -37,6 +37,7 @@ linuxmips     produces ELF executables for little-endian MIPS32r2 Linux systems
 cpm           produces i80 CP/M .COM files
 rpi           produces Raspberry Pi GPU binaries
 pdpv7         produces PDP/11 V7 Unix binaries
+msdos86       produces i86 MS-DOS .COM files