From 912d2e3c7eb1baa71dda2c0a28aa5809eaa96f27 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sat, 16 Jul 2022 13:33:00 +0200
Subject: amd64: barely boot into kernel code

---
 src/kernel/arch/amd64/tty/tty.c | 26 ++++++++++++++++++++++++++
 src/kernel/arch/amd64/tty/tty.h |  7 +++++++
 src/kernel/arch/amd64/tty/vga.c | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+)
 create mode 100644 src/kernel/arch/amd64/tty/tty.c
 create mode 100644 src/kernel/arch/amd64/tty/tty.h
 create mode 100644 src/kernel/arch/amd64/tty/vga.c

(limited to 'src/kernel/arch/amd64/tty')

diff --git a/src/kernel/arch/amd64/tty/tty.c b/src/kernel/arch/amd64/tty/tty.c
new file mode 100644
index 0000000..6593ef6
--- /dev/null
+++ b/src/kernel/arch/amd64/tty/tty.c
@@ -0,0 +1,26 @@
+#include <kernel/arch/generic.h>
+#include <kernel/arch/amd64/driver/serial.h>
+#include <kernel/arch/amd64/tty/tty.h>
+#include <shared/printf.h>
+
+void tty_init(void) {
+	vga_clear();
+	serial_preinit();
+
+	vga_write("\x03 ", 2); // cp437 heart
+	serial_write("<3 ", 3);
+}
+
+static void backend(void __attribute__((unused))  *arg, const char *buf, size_t len) {
+	vga_write(buf, len);
+	serial_write(buf, len);
+}
+
+int kprintf(const char *fmt, ...) {
+	int ret;
+	va_list argp;
+	va_start(argp, fmt);
+	ret = __printf_internal(fmt, argp, backend, NULL);
+	va_end(argp);
+	return ret;
+}
diff --git a/src/kernel/arch/amd64/tty/tty.h b/src/kernel/arch/amd64/tty/tty.h
new file mode 100644
index 0000000..b96003d
--- /dev/null
+++ b/src/kernel/arch/amd64/tty/tty.h
@@ -0,0 +1,7 @@
+#pragma once
+#include <stddef.h>
+
+void vga_write(const char *buf, size_t len);
+void vga_clear(void);
+
+void tty_init(void);
diff --git a/src/kernel/arch/amd64/tty/vga.c b/src/kernel/arch/amd64/tty/vga.c
new file mode 100644
index 0000000..e5f2274
--- /dev/null
+++ b/src/kernel/arch/amd64/tty/vga.c
@@ -0,0 +1,33 @@
+#include <kernel/arch/amd64/tty/tty.h>
+
+struct vga_cell {
+	unsigned char c;
+	unsigned char style;
+} __attribute__((__packed__));
+
+static const size_t     vga_len = 80 * 25;
+static struct vga_cell *vga     = (void*) 0xB8000;
+static size_t           vga_pos = 0;
+
+static void vga_scroll(void) {
+	for (size_t i = 0; i < vga_len - 80; i++)
+		vga[i] = vga[i + 80];
+	vga_pos -= 80;
+}
+
+static void vga_putchar(char c) {
+	if (vga_pos >= vga_len - 80)
+		vga_scroll();
+	vga[vga_pos++].c = c;
+}
+
+void vga_write(const char *buf, size_t len) {
+	for (size_t i = 0; i < len; i++)
+		vga_putchar(buf[i]);
+}
+
+void vga_clear(void) {
+	for (size_t i = 0; i < vga_len; i++)
+		vga[i].c = ' ';
+	vga_pos = 0;
+}
-- 
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