amd64: barely boot into kernel code

1 files changed, 114 insertions, 0 deletions

diff --git a/src/kernel/arch/amd64/driver/serial.c b/src/kernel/arch/amd64/driver/serial.c
new file mode 100644
index 0000000..6dda657
--- /dev/null
+++ b/src/kernel/arch/amd64/driver/serial.c
@@ -0,0 +1,114 @@
+#include <kernel/arch/amd64/driver/serial.h>
+#include <kernel/arch/amd64/interrupts/irq.h>
+#include <kernel/arch/amd64/port_io.h>
+#include <kernel/mem/virt.h>
+#include <kernel/panic.h>
+#include <shared/container/ring.h>
+#include <shared/mem.h>
+#include <stdint.h>
+
+#define BACKLOG_CAPACITY 64
+static volatile uint8_t backlog_buf[BACKLOG_CAPACITY];
+static volatile ring_t backlog = {(void*)backlog_buf, BACKLOG_CAPACITY, 0, 0};
+
+static const int COM1 = 0x3f8;
+
+static void accept(struct vfs_request *req);
+static bool is_ready(struct vfs_backend *self);
+
+static struct vfs_request *blocked_on = NULL;
+static struct vfs_backend backend = BACKEND_KERN(is_ready, accept);
+void serial_init(void) { vfs_mount_root_register("/com1", &backend); }
+
+
+static void serial_selftest(void) {
+	char b = 0x69;
+	port_out8(COM1 + 4, 0b00011110); // enable loopback mode
+	port_out8(COM1, b);
+	assert(port_in8(COM1) == b);
+}
+
+void serial_preinit(void) {
+	// see https://www.sci.muni.cz/docs/pc/serport.txt
+	// set baud rate divisor
+	port_out8(COM1 + 3, 0b10000000); // enable DLAB
+	port_out8(COM1 + 0, 0x01);       // divisor = 1 (low  byte)
+	port_out8(COM1 + 1, 0x00);       //             (high byte)
+
+	port_out8(COM1 + 3, 0b00000011); // 8 bits, no parity, one stop bit
+	port_out8(COM1 + 1, 0x01);       // enable the Data Ready IRQ
+	port_out8(COM1 + 2, 0b11000111); // enable FIFO with 14-bit trigger level (???)
+
+	serial_selftest();
+
+	port_out8(COM1 + 4, 0b00001111); // enable everything in the MCR
+}
+
+
+void serial_irq(void) {
+	ring_put1b((void*)&backlog, port_in8(COM1));
+	if (blocked_on) {
+		accept(blocked_on);
+		blocked_on = NULL;
+		vfs_backend_tryaccept(&backend);
+	}
+}
+
+
+static void serial_putchar(char c) {
+	while ((port_in8(COM1 + 5) & 0x20) == 0); // wait for THRE
+	port_out8(COM1, c);
+}
+
+void serial_write(const char *buf, size_t len) {
+	for (size_t i = 0; i < len; i++)
+		serial_putchar(buf[i]);
+}
+
+
+static void accept(struct vfs_request *req) {
+	static char buf[32];
+	int ret;
+	bool valid;
+	switch (req->type) {
+		case VFSOP_OPEN:
+			valid = req->input.len == 0;
+			vfsreq_finish_short(req, valid ? 0 : -1);
+			break;
+		case VFSOP_READ:
+			if (ring_size((void*)&backlog) == 0) {
+				/* nothing to read, join queue */
+				assert(!req->postqueue_next);
+				struct vfs_request **slot = &blocked_on;
+				while (*slot)
+					slot = &(*slot)->postqueue_next;
+				*slot = req;
+			} else if (req->caller) {
+				ret = clamp(0, req->output.len, sizeof buf);
+				ret = ring_get((void*)&backlog, buf, ret);
+				virt_cpy_to(req->caller->pages, req->output.buf, buf, ret);
+				vfsreq_finish_short(req, ret);
+			} else {
+				vfsreq_finish_short(req, -1);
+			}
+			break;
+		case VFSOP_WRITE:
+			if (req->caller) {
+				struct virt_iter iter;
+				virt_iter_new(&iter, req->input.buf, req->input.len,
+						req->caller->pages, true, false);
+				while (virt_iter_next(&iter))
+					serial_write(iter.frag, iter.frag_len);
+				ret = iter.prior;
+			} else ret = -1;
+			vfsreq_finish_short(req, ret);
+			break;
+		default:
+			vfsreq_finish_short(req, -1);
+			break;
+	}
+}
+
+static bool is_ready(struct vfs_backend __attribute__((unused)) *self) {
+	return true;
+}