Hello world over serial

kernel/amd64/io.c

@@ -0,0 +1,54 @@
+#include <libk/std.h>
+#include <amd64/io.h>
+
+void amd64_io_outb(uint16_t port, uint8_t v) {
+  __asm__ volatile("outb %1, %0" :: "dN"(port), "a"(v));
+}
+
+void amd64_io_outw(uint16_t port, uint16_t v) {
+  __asm__ volatile("outw %%ax, %%dx" :: "a"(v), "d"(port));
+}
+
+void amd64_io_outl(uint16_t port, uint32_t v) {
+  __asm__ volatile("outl %%eax, %%dx" :: "d"(port), "a"(v));
+}
+
+void amd64_io_outsw(uint16_t port, const void *addr, int cnt) {
+  __asm__ volatile(
+    "cld; rep outsw"
+    : "+S"(addr), "+c"(cnt)
+    : "d"(port)
+    : "memory", "cc"
+  );
+}
+
+uint8_t amd64_io_inb(uint16_t port) {
+  uint8_t r;
+  __asm__ volatile("inb %1, %0" : "=a"(r) : "dN"(port));
+  return r;
+}
+
+uint16_t amd64_io_inw(uint16_t port) {
+  uint16_t r;
+  __asm__ volatile("inw %%dx, %%ax" : "=a"(r) : "d"(port));
+  return r;
+}
+
+uint32_t amd64_io_inl(uint16_t port) {
+  uint32_t r;
+  __asm__ volatile("inl %%dx, %%eax" : "=a"(r) : "d"(port));
+  return r;
+}
+
+void amd64_io_insw(uint16_t port, void *addr, int cnt) {
+  __asm__ volatile(
+    "cld; rep insw"
+    : "+D"(addr), "+c"(cnt)
+    : "d"(port)
+    : "memory", "cc"
+  );
+}
+
+void amd64_io_wait(void) {
+  amd64_io_outb(0x80, 0);
+}