Add subprocesses and convert terminal to an app

src/kernel/kernel.c

@@ -7,8 +7,10 @@
 #include "src/kernel/pic.h"
 #include "src/kernel/process.h"
 #include "src/kernel/syscall.h"
+#include "src/kernel/tss.h"
 #include "src/kernel/util.h"
 #include "src/kernel/vga.h"
+#include "src/lib/layout.h"
 #include "src/lib/memory.h"
 
 __attribute__((interrupt)) void isr_divide_by_zero(__attribute__((unused)) struct interrupt_frame *frame) {
@@ -47,30 +49,39 @@ void kernel_main() {
   gdt_init();
   syscall_init();
 
-  process_t *kp = memory_allocate(sizeof(process_t));
-  kp->root = fs_mount();
-  kp->cwd = memory_allocate(sizeof(path_t));
-  kp->stdin = keyboard_init();
-  kp->stdout = vga_init();
+  process_t *kernel = memory_allocate(sizeof(process_t));
+  kernel->pml4 = (void *)KERNEL_VIRTUAL_PML4;
+  kernel->root = fs_mount();
+  kernel->cwd = memory_allocate(sizeof(path_t));
+  kernel->stdin = keyboard_init();
+  kernel->stdout = vga_init();
 
-  fs_node_t *hello = fs_open_by(kp->root, "HELLO.BIN");
+  fs_node_t *bin = fs_open_by(kernel->root, "terminal");
 
-  ASSERT(hello, "kernel: hello.bin not found");
+  ASSERT(bin, "kernel: terminal not found");
 
-  uint8_t *hello_code = memory_allocate(hello->size);
-  fs_read(hello, 0, hello->size, hello_code);
+  uint8_t *code = memory_allocate(bin->size);
+  fs_read(bin, 0, bin->size, code);
 
-  process_t *proc = process_create(kp, hello_code, hello->size);
+  process_t *terminal = process_create(kernel, code, bin->size);
 
-  memory_free(hello_code);
-  fs_close(hello);
+  memory_free(code);
+  fs_close(bin);
 
-  process_run(proc);
+  __asm__ volatile("mov %0, %%cr3" : : "r"((uint64_t)VIRT_TO_PHYS((void *)KERNEL_VIRTUAL_PML4)) : "memory");
 
-  while (1)
-    ;
+  uint8_t *stack = (uint8_t *)terminal->user_stack;
 
-  fs_unmount(kp->root);
+  stack -= sizeof(uint64_t);
+  *(uint64_t *)stack = 0;
+
+  terminal->user_rsp = (void *)(USER_VIRTUAL_STACK_TOP - ((uint64_t)terminal->user_stack - (uint64_t)stack));
+
+  current_process = terminal;
+  tss.rsp0 = (uint64_t)current_process->kernel_stack;
+  process_switch_to(&kernel->kernel_rsp, terminal->kernel_rsp, VIRT_TO_PHYS(terminal->pml4));
+
+  fs_unmount((fs_node_t *)kernel->root);
 
   outw(0x604, 0x2000); // TODO: parse ACPI tables for real hardware
   __asm__ volatile("cli; hlt");