Turn the syscall interrupt into a trap (by switching the gate type.)

This leaves interrupts enabled while we're in the kernel, which is
precisely what we want.

This uncovered a horrendous problem with kernel tasks silently
overflowing their stacks. For now I've simply increased the stack size
but I need a more MMU-y solution for this eventually.

Kernel/Task.cpp

@@ -162,13 +162,14 @@ Task::Task(void (*e)(), const char* n, IPC::Handle h, RingLevel ring)
 
     kprintf("basically ready\n");
 
-    // NOTE: Each task gets 4KB of stack.
-    static const DWORD defaultStackSize = 4096;
+    // NOTE: Each task gets 16KB of stack.
+    static const DWORD defaultStackSize = 16384;
 
     if (isRing0()) {
         // FIXME: This memory is leaked.
         // But uh, there's also no kernel task termination, so I guess it's not technically leaked...
-        m_stackTop = ((DWORD)kmalloc(defaultStackSize) + defaultStackSize) & 0xffffff8;
+        dword stackBottom = (dword)kmalloc(defaultStackSize);
+        m_stackTop = (stackBottom + defaultStackSize) & 0xffffff8;
         m_tss.esp = m_stackTop;
     } else {
         auto* region = allocateRegion(defaultStackSize, "stack");
@@ -235,8 +236,8 @@ void Task::dumpRegions()
 
 void Task::taskDidCrash(Task* crashedTask)
 {
+    // NOTE: This is called from an excepton handler, so interrupts are disabled.
     crashedTask->setState(Crashing);
-
     crashedTask->dumpRegions();
 
     s_tasks->remove(crashedTask);
@@ -260,8 +261,11 @@ void yield()
 
     //kprintf("%s<%u> yield()\n", current->name().characters(), current->pid());
 
-    if (!scheduleNewTask())
+    cli();
+    if (!scheduleNewTask()) {
+        sti();
         return;
+    }
 
     //kprintf("yield() jumping to new task: %x (%s)\n", current->farPtr().selector, current->name().characters());
     switchNow();
@@ -272,7 +276,7 @@ void switchNow()
     Descriptor& descriptor = getGDTEntry(current->selector());
     descriptor.type = 9;
     flushGDT();
-    asm(
+    asm("sti\n"
         "ljmp *(%%eax)\n"
         ::"a"(&current->farPtr())
     );

Kernel/i386.cpp

@@ -68,6 +68,67 @@ asm( \
     "    iret\n" \
 );
 
+#define EH_ENTRY_NO_CODE(ec) \
+extern "C" void exception_ ## ec ## _handler(); \
+extern "C" void exception_ ## ec ## _entry(); \
+asm( \
+    ".globl exception_" # ec "_entry\n" \
+    "exception_" # ec "_entry: \n" \
+    "    pusha\n" \
+    "    pushw %ds\n" \
+    "    pushw %es\n" \
+    "    pushw %fs\n" \
+    "    pushw %gs\n" \
+    "    pushw %ss\n" \
+    "    pushw %ss\n" \
+    "    pushw %ss\n" \
+    "    pushw %ss\n" \
+    "    popw %ds\n" \
+    "    popw %es\n" \
+    "    popw %fs\n" \
+    "    popw %gs\n" \
+    "    mov %esp, exception_state_dump\n" \
+    "    call exception_" # ec "_handler\n" \
+    "    popw %gs\n" \
+    "    popw %fs\n" \
+    "    popw %es\n" \
+    "    popw %ds\n" \
+    "    popa\n" \
+    "    iret\n" \
+);
+
+// 6: Invalid Opcode
+EH_ENTRY_NO_CODE(6);
+void exception_6_handler()
+{
+    auto& regs = *reinterpret_cast<RegisterDump*>(exception_state_dump);
+    kprintf("%s invalid opcode: %u(%s)\n", current->isRing0() ? "Kernel" : "Process", current->pid(), current->name().characters());
+
+    word ss;
+    dword esp;
+    if (current->isRing0()) {
+        ss = regs.ds;
+        esp = regs.esp;
+    } else {
+        ss = regs.ss_if_crossRing;
+        esp = regs.esp_if_crossRing;
+    }
+
+    kprintf("exception code: %w\n", exception_code);
+    kprintf("pc=%w:%x ds=%w es=%w fs=%w gs=%w\n", regs.cs, regs.eip, regs.ds, regs.es, regs.fs, regs.gs);
+    kprintf("eax=%x ebx=%x ecx=%x edx=%x\n", regs.eax, regs.ebx, regs.ecx, regs.edx);
+    kprintf("ebp=%x esp=%x esi=%x edi=%x\n", regs.ebp, esp, regs.esi, regs.edi);
+
+    if (current->isRing0()) {
+        kprintf("Oh shit, we've crashed in ring 0 :(\n");
+        HANG;
+    }
+    HANG;
+
+    // NOTE: This will schedule a new task.
+    Task::taskDidCrash(current);
+}
+
 // 13: General Protection Fault
 EH_ENTRY(13);
 void exception_13_handler()
@@ -239,7 +300,7 @@ void registerInterruptHandler(BYTE index, void (*f)())
 void registerUserCallableInterruptHandler(BYTE index, void (*f)())
 {
     s_idt[index].low = 0x00080000 | LSW((f));
-    s_idt[index].high = ((DWORD)(f) & 0xffff0000) | 0xee00;
+    s_idt[index].high = ((DWORD)(f) & 0xffff0000) | 0xef00;
     flushIDT();
 }
 
@@ -276,7 +337,7 @@ void idt_init()
     registerInterruptHandler(0x03, _exception3);
     registerInterruptHandler(0x04, _exception4);
     registerInterruptHandler(0x05, _exception5);
-    registerInterruptHandler(0x06, _exception6);
+    registerInterruptHandler(0x06, exception_6_entry);
     registerInterruptHandler(0x07, _exception7);
     registerInterruptHandler(0x08, _exception8);
     registerInterruptHandler(0x09, _exception9);

Kernel/i386.h

@@ -72,8 +72,8 @@ void writeGDTEntry(WORD selector, Descriptor&);
 #define LSB(x) ((x) & 0xFF)
 #define MSB(x) (((x)>>8) & 0xFF)
 
-#define disableInterrupts() asm volatile("cli");
-#define enableInterrupts() asm volatile("sti");
+#define cli() asm volatile("cli")
+#define sti() asm volatile("sti")
 
 /* Map IRQ0-15 @ ISR 0x50-0x5F */
 #define IRQ_VECTOR_BASE 0x50

Kernel/i8253.cpp

@@ -98,11 +98,12 @@ void clock_handle()
     WORD foo = vga_get_cursor();
 
     vga_set_attr(0x50);
-    vga_set_cursor(1600);
+    vga_set_cursor(0);
 
-    kprintf("Task %u interrupted at %x\n", current->pid(), regs.eip );
-    kprintf("EAX=%x EBX=%x ECX=%x EDX=%x\n", regs.eax, regs.ebx, regs.ecx, regs.edx);
-    kprintf("ESI=%x EDI=%x EBP=%x ESP=%x\n", regs.esi, regs.edi, regs.ebp, regs.esp);
+    kprintf("\n\n");
+    kprintf("Task %u interrupted at %x             \n", current->pid(), regs.eip );
+    kprintf("EAX=%x EBX=%x ECX=%x EDX=%x           \n", regs.eax, regs.ebx, regs.ecx, regs.edx);
+    kprintf("ESI=%x EDI=%x EBP=%x ESP=%x           \n", regs.esi, regs.edi, regs.ebp, regs.esp);
     kprintf("FLAGS=%x", regs.eflags);
 
     vga_set_cursor(foo);
@@ -111,6 +112,9 @@ void clock_handle()
 
     // Compute task ESP.
     // Add 12 for CS, EIP, EFLAGS (interrupt mechanic)
+
+    // FIXME: Hmm. Should we add an extra 8 here for SS:ESP in some cases?
+    //        If this IRQ occurred while in a user task, wouldn't that also push the stack ptr?
     current->tss().esp = regs.esp + 12;
 
     // Prepare a new task to run;

Kernel/init.cpp

@@ -25,6 +25,9 @@
 #include "MemoryManager.h"
 #include <ELFLoader/ELFLoader.h>
 
+#define TEST_ELF_LOADER
+#define TEST_CRASHY_USER_PROCESSES
+
 #if 0
 /* Keyboard LED disco task ;^) */
 
@@ -63,6 +66,18 @@ static void motd_main()
     }
 }
 
+static void syscall_test_main() NORETURN;
+static void syscall_test_main()
+{
+    kprintf("Hello in syscall_test_main!\n");
+    for (;;) {
+        Userspace::getuid();
+//        Userspace::yield();
+        //kprintf("getuid(): %u\n", Userspace::getuid());
+        sleep(1 * TICKS_PER_SECOND);
+    }
+}
+
 static void user_main() NORETURN;
 static void user_main()
 {
@@ -106,7 +121,7 @@ void banner()
 
 void init()
 {
-    disableInterrupts();
+    cli();
 
     kmalloc_init();
     vga_init();
@@ -123,6 +138,8 @@ void init()
     Keyboard::initialize();
     Task::initialize();
 
+    VirtualFileSystem::initializeGlobals();
+
     memset(&system, 0, sizeof(system));
 
     WORD base_memory = (CMOS::read(0x16) << 8) | CMOS::read(0x15);
@@ -138,12 +155,12 @@ void init()
     //new Task(led_disco, "led-disco", IPC::Handle::Any, Task::Ring0);
 
     scheduleNewTask();
-    enableInterrupts();
-
     banner();
+    sti();
 
     Disk::initialize();
 
+#if 1
     auto vfs = make<VirtualFileSystem>();
 
     auto dev_zero = make<ZeroDevice>();
@@ -164,11 +181,13 @@ void init()
 
     vfs->mountRoot(e2fs.copyRef());
 
-    //new Task(motd_main, "motd", IPC::Handle::MotdTask, Task::Ring0);
+#ifdef TEST_CRASHY_USER_PROCESSES
     new Task(user_main, "user", IPC::Handle::UserTask, Task::Ring3);
     new Task(user_kprintf_main, "user_kprintf", IPC::Handle::UserTask, Task::Ring3);
+#endif
 
     //vfs->listDirectory("/");
+#endif
 
 #if 1
     {
@@ -182,6 +201,7 @@ void init()
     }
 #endif
 
+#ifdef TEST_ELF_LOADER
     {
         auto testExecutable = vfs->open("/_hello.o");
         ASSERT(testExecutable);
@@ -197,9 +217,11 @@ void init()
         kprintf("elf_entry: %p\n", elf_entry);
         int rc = reinterpret_cast<MainFunctionPtr>(elf_entry)();
         kprintf("it returned %d\n", rc);
-
-        HANG;
     }
+#endif
+
+    new Task(motd_main, "motd", IPC::Handle::MotdTask, Task::Ring0);
+    new Task(syscall_test_main, "syscall_test", IPC::Handle::MotdTask, Task::Ring0);
 
     // The idle task will spend its eternity here for now.
     for (;;) {

Kernel/panel.cpp

@@ -16,12 +16,12 @@ panel_main()
 
     for( ;; )
     {
-        c = vga_get_cursor();
-        a = vga_get_attr();
-
         /* HACK: Avoid getting interrupted while painting since
          *       that could lead to fugly artifacts ;P */
-        disableInterrupts();
+        cli();
+
+        c = vga_get_cursor();
+        a = vga_get_attr();
 
         vga_set_attr( 0x17 );
         vga_set_cursor( 80 * 24 );
@@ -39,7 +39,7 @@ panel_main()
         vga_set_cursor( c );
 
         /* HACK cont.d */
-        enableInterrupts();
+        sti();
 
         sleep( 1 * TICKS_PER_SECOND );
     }