Add VGA support on bare metal (#588)

If your main module has this declaration:

    STATIC_YOINK("vga_console");

Then a VGA driver will be linked into your executable which
displays your stdio characters on the PC display, whereas
before we could only use the serial port. Your display is an
ANSI terminal and it's still a work in progress.

Makefile

@@ -117,7 +117,8 @@ include third_party/xed/xed.mk			# │
 include third_party/zlib/zlib.mk		# │
 include libc/elf/elf.mk				# │
 include ape/ape.mk				# │
-include libc/fmt/fmt.mk				#─┘
+include libc/fmt/fmt.mk				# │
+include libc/vga/vga.mk				#─┘
 include libc/calls/calls.mk			#─┐
 include libc/runtime/runtime.mk			# ├──SYSTEMS RUNTIME
 include libc/crt/crt.mk				# │  You can issue system calls
@@ -318,7 +319,8 @@ COSMOPOLITAN_OBJECTS =		\
 	LIBC_SYSV		\
 	LIBC_INTRIN		\
 	LIBC_NT_KERNEL32	\
-	LIBC_NEXGEN32E
+	LIBC_NEXGEN32E		\
+	LIBC_VGA
 
 COSMOPOLITAN_HEADERS =		\
 	APE			\
@@ -343,6 +345,7 @@ COSMOPOLITAN_HEADERS =		\
 	LIBC_TINYMATH		\
 	LIBC_X			\
 	LIBC_ZIPOS		\
+	LIBC_VGA		\
 	NET_HTTP		\
 	THIRD_PARTY_DLMALLOC	\
 	THIRD_PARTY_GDTOA	\

examples/examples.mk

@@ -66,6 +66,7 @@ EXAMPLES_DIRECTDEPS =								\
 	LIBC_THREAD								\
 	LIBC_TIME								\
 	LIBC_TINYMATH								\
+	LIBC_VGA								\
 	LIBC_X									\
 	LIBC_ZIPOS								\
 	NET_HTTP								\

examples/hello4.c

@@ -10,6 +10,8 @@
 #include "libc/math.h"
 #include "libc/stdio/stdio.h"
 
+STATIC_YOINK("vga_console");
+
 int main(int argc, char *argv[]) {
   volatile long double x = -.5;
   volatile long double y = 1.5;

libc/calls/writev-metal.c

@@ -19,10 +19,16 @@
 #include "libc/calls/struct/fd.internal.h"
 #include "libc/calls/struct/iovec.h"
 #include "libc/calls/struct/iovec.internal.h"
+#include "libc/intrin/weaken.h"
 #include "libc/sysv/errfuns.h"
+#include "libc/vga/vga.internal.h"
 
 ssize_t sys_writev_metal(struct Fd *fd, const struct iovec *iov, int iovlen) {
   switch (fd->kind) {
+    case kFdConsole:
+      if (weaken(sys_writev_vga))
+        weaken(sys_writev_vga)(fd, iov, iovlen);
+      /* fallthrough */
     case kFdSerial:
       return sys_writev_serial(fd, iov, iovlen);
     default:

libc/intrin/g_fds.c

@@ -21,6 +21,7 @@
 #include "libc/intrin/pthread.h"
 #include "libc/intrin/pushpop.h"
 #include "libc/intrin/spinlock.h"
+#include "libc/intrin/weaken.h"
 #include "libc/nt/runtime.h"
 #include "libc/sysv/consts/o.h"
 
@@ -55,10 +56,17 @@ textstartup void InitializeFileDescriptors(void) {
   fds->f = 3;
   fds->p = fds->__init_p;
   if (IsMetal()) {
+    extern const char vga_console[];
     pushmov(&fds->f, 3ull);
+    if (weaken(vga_console)) {
+      fds->__init_p[0].kind = pushpop(kFdConsole);
+      fds->__init_p[1].kind = pushpop(kFdConsole);
+      fds->__init_p[2].kind = pushpop(kFdConsole);
+    } else {
       fds->__init_p[0].kind = pushpop(kFdSerial);
       fds->__init_p[1].kind = pushpop(kFdSerial);
       fds->__init_p[2].kind = pushpop(kFdSerial);
+    }
     fds->__init_p[0].handle = VEIL("r", 0x3F8ull);
     fds->__init_p[1].handle = VEIL("r", 0x3F8ull);
     fds->__init_p[2].handle = VEIL("r", 0x3F8ull);

libc/libc.mk

@@ -30,6 +30,7 @@ o/$(MODE)/libc:	o/$(MODE)/libc/calls		\
 		o/$(MODE)/libc/thread		\
 		o/$(MODE)/libc/time		\
 		o/$(MODE)/libc/tinymath		\
+		o/$(MODE)/libc/vga		\
 		o/$(MODE)/libc/x		\
 		o/$(MODE)/libc/zipos		\
 		$(LIBC_CHECKS)

libc/vga/vga-init.S

@@ -0,0 +1,66 @@
+/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
+│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ This is free and unencumbered software released into the public domain.      │
+│                                                                              │
+│ Anyone is free to copy, modify, publish, use, compile, sell, or              │
+│ distribute this software, either in source code form or as a compiled        │
+│ binary, for any purpose, commercial or non-commercial, and by any            │
+│ means.                                                                       │
+│                                                                              │
+│ In jurisdictions that recognize copyright laws, the author or authors        │
+│ of this software dedicate any and all copyright interest in the              │
+│ software to the public domain. We make this dedication for the benefit       │
+│ of the public at large and to the detriment of our heirs and                 │
+│ successors. We intend this dedication to be an overt act of                  │
+│ relinquishment in perpetuity of all present and future rights to this        │
+│ software under copyright law.                                                │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,              │
+│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF           │
+│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.       │
+│ IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR            │
+│ OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,        │
+│ ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR        │
+│ OTHER DEALINGS IN THE SOFTWARE.                                              │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/macros.internal.h"
+
+//	Code snippet for initializing the VGA video mode for bare metal.
+//
+//	If a program requests VGA support (by yoinking vga_console),
+//	and it is started in bare metal mode, then try to ensure that
+//	the VGA monitor is in a known mode.  This is easier to do while
+//	the program is still running in real mode.
+//
+//	This module also ropes in the sys_writev_vga routine, which
+//	implements the actual VGA console output under x86-64 long mode.
+//
+//	@see	rlinit & .sort.text.real.init.* (ape/ape.S)
+//	@see	ape/ape.lds
+//	@see	sys_writev_vga (libc/vga/writev-vga.c)
+	.section .sort.text.real.init.2,"ax",@progbits
+	.code16
+	mov	$0x4f03,%ax		# get current video mode via VESA
+	int	$0x10
+	cmp	$0x004f,%ax		# is VESA a thing here?
+	jz	1f
+	mov	$0x0f,%ah		# if not, get the video mode via a
+	int	$0x10			# classical BIOS call
+	cbtw
+	xchgw	%ax,%bx
+1:	mov	$0x0003,%ax		# check if we are in a 80 × ? × 16
+	cmp	%ax,%bx			# text mode
+	jnz	2f
+	cmpb	$25-1,0x0484		# check if number of screen rows
+	jnz	2f			# (BDA.ROWS + 1) is 25; if so, then
+	mov	$0x0500,%ax		# just make sure we are on display
+					# page 0
+2:	int	$0x10			# otherwise, change the video mode
+	.previous
+	.code64
+	.section .rodata,"a",@progbits
+vga_console:
+	.endobj	vga_console,globl,hidden
+	.previous
+	.yoink	sys_writev_vga

libc/vga/vga.internal.h

@@ -0,0 +1,118 @@
+#ifndef COSMOPOLITAN_LIBC_VGA_VGA_INTERNAL_H_
+#define COSMOPOLITAN_LIBC_VGA_VGA_INTERNAL_H_
+
+/*
+ * VGA_TTY_HEIGHT, VGA_TTY_WIDTH, & VGA_USE_WCS are configuration knobs
+ * which can potentially be used to tweak the features to be compiled into
+ * our VGA teletypewriter support.
+ */
+
+/**
+ * Height of the video screen, in character units.  Undefine if the height
+ * may vary at runtime.
+ */
+#define VGA_TTY_HEIGHT 25
+/**
+ * Width of the video screen, in character units.  Undefine if the width may
+ * vary at runtime.
+ */
+#define VGA_TTY_WIDTH 80
+/**
+ * If VGA_USE_WCS is defined, the tty code can maintain an array of the
+ * Unicode characters "underlying" the 8-bit (or 9-bit) characters that are
+ * actually displayed on the text screen.  This can be used to implement
+ * something similar to Linux's /dev/vcsu* facility.
+ *
+ * @see lkml.kernel.org/lkml/204888.1529277815@turing-police.cc.vt.edu/T/
+ */
+#undef VGA_USE_WCS
+
+#define kTtyFg      0x0001
+#define kTtyBg      0x0002
+#define kTtyBold    0x0004
+#define kTtyFlip    0x0008
+#define kTtyFaint   0x0010
+#define kTtyUnder   0x0020
+#define kTtyDunder  0x0040
+#define kTtyTrue    0x0080
+#define kTtyBlink   0x0100
+#define kTtyItalic  0x0200
+#define kTtyFraktur 0x0400
+#define kTtyStrike  0x0800
+#define kTtyConceal 0x1000
+
+#define kTtyBell        0x001
+#define kTtyRedzone     0x002
+#define kTtyNocursor    0x004
+#define kTtyBlinkcursor 0x008
+#define kTtyNocanon     0x010
+#define kTtyNoecho      0x020
+#define kTtyNoopost     0x040
+#define kTtyLed1        0x080
+#define kTtyLed2        0x100
+#define kTtyLed3        0x200
+#define kTtyLed4        0x400
+
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+#include "libc/calls/struct/fd.internal.h"
+#include "libc/calls/struct/iovec.h"
+#include "libc/calls/struct/iovec.internal.h"
+
+COSMOPOLITAN_C_START_
+
+struct VgaTextCharCell {
+  uint8_t ch, attr;
+};
+
+struct Tty {
+  unsigned short y, x;
+#ifndef VGA_TTY_HEIGHT
+  unsigned short yn;
+#endif
+#ifndef VGA_TTY_WIDTH
+  unsigned short xn;
+#endif
+  uint32_t u8;
+  uint32_t n8;
+  uint32_t pr;
+  uint8_t fg, bg;
+  uint32_t conf;
+  unsigned short savey, savex;
+  struct VgaTextCharCell *ccs;
+#ifdef VGA_USE_WCS
+  wchar_t *wcs;
+#endif
+  wchar_t *xlat;
+  enum TtyState {
+    kTtyAscii,
+    kTtyUtf8,
+    kTtyEsc,
+    kTtyCsi,
+  } state;
+  struct TtyEsc {
+    unsigned i;
+    char s[64];
+  } esc;
+  struct TtyInput {
+    size_t i;
+    char p[256];
+  } input;
+};
+
+void _StartTty(struct Tty *, unsigned short, unsigned short,
+               unsigned short, unsigned short, void *, wchar_t *);
+ssize_t _TtyRead(struct Tty *, void *, size_t);
+ssize_t _TtyWrite(struct Tty *, const void *, size_t);
+ssize_t _TtyWriteInput(struct Tty *, const void *, size_t);
+void _TtyResetOutputMode(struct Tty *);
+void _TtyFullReset(struct Tty *);
+void _TtyMemmove(struct Tty *, size_t, size_t, size_t);
+void _TtyErase(struct Tty *, size_t, size_t);
+void _TtySetY(struct Tty *, unsigned short);
+void _TtySetX(struct Tty *, unsigned short);
+
+ssize_t sys_writev_vga(struct Fd *, const struct iovec *, int);
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_VGA_VGA_INTERNAL_H_ */

libc/vga/vga.mk

@@ -0,0 +1,58 @@
+#-*-mode:makefile-gmake;indent-tabs-mode:t;tab-width:8;coding:utf-8-*-┐
+#───vi: set et ft=make ts=8 tw=8 fenc=utf-8 :vi───────────────────────┘
+
+PKGS += LIBC_VGA
+
+LIBC_VGA_ARTIFACTS += LIBC_VGA_A
+LIBC_VGA_A = o/$(MODE)/libc/vga/vga.a
+LIBC_VGA_A_FILES := $(wildcard libc/vga/*)
+LIBC_VGA_A_HDRS = $(filter %.h,$(LIBC_VGA_A_FILES))
+LIBC_VGA_A_SRCS_S = $(filter %.S,$(LIBC_VGA_A_FILES))
+LIBC_VGA_A_SRCS_C = $(filter %.c,$(LIBC_VGA_A_FILES))
+
+LIBC_VGA =						\
+	$(LIBC_VGA_A_DEPS)				\
+	$(LIBC_VGA_A)
+
+LIBC_VGA_A_SRCS =					\
+	$(LIBC_VGA_A_SRCS_S)				\
+	$(LIBC_VGA_A_SRCS_C)
+
+LIBC_VGA_A_OBJS =					\
+	$(LIBC_VGA_A_SRCS_S:%.S=o/$(MODE)/%.o)		\
+	$(LIBC_VGA_A_SRCS_C:%.c=o/$(MODE)/%.o)
+
+LIBC_VGA_A_CHECKS =					\
+	$(LIBC_VGA_A).pkg				\
+	$(LIBC_VGA_A_HDRS:%=o/$(MODE)/%.ok)
+
+LIBC_VGA_A_DIRECTDEPS =					\
+	LIBC_NEXGEN32E					\
+	LIBC_SYSV					\
+	LIBC_STR					\
+	LIBC_INTRIN					\
+	LIBC_STUBS					\
+	LIBC_FMT
+
+LIBC_VGA_A_DEPS :=					\
+	$(call uniq,$(foreach x,$(LIBC_VGA_A_DIRECTDEPS),$($(x))))
+
+$(LIBC_VGA_A):libc/vga/					\
+		$(LIBC_VGA_A).pkg			\
+		$(LIBC_VGA_A_OBJS)
+
+$(LIBC_VGA_A).pkg:					\
+		$(LIBC_VGA_A_OBJS)			\
+		$(foreach x,$(LIBC_VGA_A_DIRECTDEPS),$($(x)_A).pkg)
+
+LIBC_VGA_LIBS = $(foreach x,$(LIBC_VGA_ARTIFACTS),$($(x)))
+LIBC_VGA_SRCS = $(foreach x,$(LIBC_VGA_ARTIFACTS),$($(x)_SRCS))
+LIBC_VGA_HDRS = $(foreach x,$(LIBC_VGA_ARTIFACTS),$($(x)_HDRS))
+LIBC_VGA_BINS = $(foreach x,$(LIBC_VGA_ARTIFACTS),$($(x)_BINS))
+LIBC_VGA_CHECKS = $(foreach x,$(LIBC_VGA_ARTIFACTS),$($(x)_CHECKS))
+LIBC_VGA_OBJS = $(foreach x,$(LIBC_VGA_ARTIFACTS),$($(x)_OBJS))
+LIBC_VGA_TESTS = $(foreach x,$(LIBC_VGA_ARTIFACTS),$($(x)_TESTS))
+$(LIBC_VGA_OBJS): $(BUILD_FILES) libc/vga/vga.mk
+
+.PHONY: o/$(MODE)/libc/vga
+o/$(MODE)/libc/vga: $(LIBC_VGA_CHECKS)

libc/vga/writev-vga.c

@@ -0,0 +1,72 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ This is free and unencumbered software released into the public domain.      │
+│                                                                              │
+│ Anyone is free to copy, modify, publish, use, compile, sell, or              │
+│ distribute this software, either in source code form or as a compiled        │
+│ binary, for any purpose, commercial or non-commercial, and by any            │
+│ means.                                                                       │
+│                                                                              │
+│ In jurisdictions that recognize copyright laws, the author or authors        │
+│ of this software dedicate any and all copyright interest in the              │
+│ software to the public domain. We make this dedication for the benefit       │
+│ of the public at large and to the detriment of our heirs and                 │
+│ successors. We intend this dedication to be an overt act of                  │
+│ relinquishment in perpetuity of all present and future rights to this        │
+│ software under copyright law.                                                │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,              │
+│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF           │
+│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.       │
+│ IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR            │
+│ OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,        │
+│ ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR        │
+│ OTHER DEALINGS IN THE SOFTWARE.                                              │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/struct/fd.internal.h"
+#include "libc/calls/struct/iovec.h"
+#include "libc/calls/struct/iovec.internal.h"
+#include "libc/vga/vga.internal.h"
+#include "libc/runtime/pc.internal.h"
+#include "libc/str/str.h"
+
+static struct Tty vga_tty;
+#ifdef VGA_USE_WCS
+static wchar_t vga_wcs[VGA_TTY_HEIGHT * VGA_TTY_WIDTH];
+#else
+static wchar_t * const vga_wcs = NULL;
+#endif
+
+ssize_t sys_writev_vga(struct Fd *fd, const struct iovec *iov, int iovlen) {
+  size_t i, wrote = 0;
+  ssize_t res = 0;
+  for (i = 0; i < iovlen; ++i) {
+    void *input = iov[i].iov_base;
+    size_t len = iov[i].iov_len;
+    res = _TtyWrite(&vga_tty, input, len);
+    if (res < 0)
+      break;
+    wrote += res;
+    if (res != len)
+      return wrote;
+  }
+  if (!wrote)
+    return res;
+  return wrote;
+}
+
+__attribute__((__constructor__)) static textstartup void _vga_init(void) {
+  void * const vid_buf = (void *)(BANE + 0xb8000ull);
+  /* Get the initial cursor position from the BIOS data area. */
+  typedef struct {
+    unsigned char col, row;
+  } bios_curs_pos_t;
+  bios_curs_pos_t pos = *(bios_curs_pos_t *)(BANE + 0x0450ull);
+  /*
+   * Initialize our tty structure from the current screen contents & current
+   * cursor position.
+   */
+  _StartTty(&vga_tty, VGA_TTY_HEIGHT, VGA_TTY_WIDTH, pos.row, pos.col,
+            vid_buf, vga_wcs);
+}