Waiters should be notified when a waitee is killed.

Ran into a horrendous bug where VirtualConsole would overrun its buffer
and scribble right into some other object if we were interrupted while
processing a character. Slapped an InterruptDisabler onto onChar for now.

This provokes an interesting question though.. if a process is killed
while its in kernel space, how the heck do we release any locks it held?
I'm sure there are many different solutions to this problem, but I'll
have to think about it.

Kernel/Task.cpp

@@ -518,6 +518,15 @@ void Task::dumpRegions()
     }
 }
 
+void Task::notify_waiters(pid_t waitee, int exit_status, int signal)
+{
+    ASSERT_INTERRUPTS_DISABLED();
+    for (auto* task = s_tasks->head(); task; task = task->next()) {
+        if (task->waitee() == waitee)
+            task->m_waiteeStatus = (exit_status << 8) | (signal);
+    }
+}
+
 void Task::sys$exit(int status)
 {
     cli();
@@ -531,10 +540,7 @@ void Task::sys$exit(int status)
 
     s_tasks->remove(this);
 
-    for (auto* task = s_tasks->head(); task; task = task->next()) {
-        if (task->waitee() == m_pid)
-            task->m_waiteeStatus = status << 8;
-    }
+    notify_waiters(m_pid, status, 0);
 
     if (!scheduleNewTask()) {
         kprintf("Task::sys$exit: Failed to schedule a new task :(\n");
@@ -546,13 +552,17 @@ void Task::sys$exit(int status)
     switchNow();
 }
 
-void Task::murder()
+void Task::murder(int signal)
 {
     ASSERT_INTERRUPTS_DISABLED();
     bool wasCurrent = current == this;
     setState(Exiting);
     s_tasks->remove(this);
+
+    notify_waiters(m_pid, 0, signal);
+
     if (wasCurrent) {
+        kprintf("Current task committing suicide!\n");
         MM.unmapRegionsForTask(*this);
         if (!scheduleNewTask()) {
             kprintf("Task::murder: Failed to schedule a new task :(\n");
@@ -578,6 +588,8 @@ void Task::taskDidCrash(Task* crashedTask)
 
     s_tasks->remove(crashedTask);
 
+    notify_waiters(crashedTask->m_pid, 0, SIGSEGV);
+
     MM.unmapRegionsForTask(*crashedTask);
 
     if (!scheduleNewTask()) {
@@ -991,8 +1003,9 @@ int Task::sys$kill(pid_t pid, int sig)
     auto* peer = Task::fromPID(pid);
     if (!peer)
         return -ESRCH;
-    if (sig == 9) {
-        peer->murder();
+    if (sig == SIGKILL) {
+        peer->murder(SIGKILL);
+        return 0;
     } else {
         ASSERT_NOT_REACHED();
     }

Kernel/Task.h

@@ -218,7 +218,8 @@ private:
 
     pid_t m_parentPID { 0 };
 
-    void murder();
+    static void notify_waiters(pid_t waitee, int exit_status, int signal);
+    void murder(int signal);
 
     Vector<String> m_arguments;
     Vector<String> m_initialEnvironment;

Kernel/VirtualConsole.cpp

@@ -300,6 +300,8 @@ void VirtualConsole::scrollUp()
 
 void VirtualConsole::setCursor(unsigned row, unsigned column)
 {
+    ASSERT(row < m_rows);
+    ASSERT(column < m_columns);
     m_cursorRow = row;
     m_cursorColumn = column;
     if (m_active)
@@ -308,6 +310,8 @@ void VirtualConsole::setCursor(unsigned row, unsigned column)
 
 void VirtualConsole::putCharacterAt(unsigned row, unsigned column, byte ch)
 {
+    ASSERT(row < m_rows);
+    ASSERT(column < m_columns);
     word cur = (row * 160) + (column * 2);
     m_buffer[cur] = ch;
     m_buffer[cur + 1] = m_currentAttribute;
@@ -317,6 +321,7 @@ void VirtualConsole::putCharacterAt(unsigned row, unsigned column, byte ch)
 
 void VirtualConsole::onChar(byte ch, bool shouldEmit)
 {
+    InterruptDisabler disabler;
     if (shouldEmit)
         emit(ch);
 

LibC/unistd.h

@@ -30,6 +30,7 @@ off_t lseek(int fd, off_t, int whence);
 #define WEXITSTATUS(status) (((status) & 0xff00) >> 8)
 #define WTERMSIG(status) ((status) & 0x7f)
 #define WIFEXITED(status) (WTERMSIG(status) == 0)
+#define WIFSIGNALED(status) (((char) (((status) & 0x7f) + 1) >> 1) > 0)
 
 #define HOST_NAME_MAX 64
 

VirtualFileSystem/FileHandle.cpp

@@ -5,6 +5,7 @@
 #include "UnixTypes.h"
 #include "TTY.h"
 #include <AK/BufferStream.h>
+#include <Kernel/Task.h>
 
 FileHandle::FileHandle(RetainPtr<VirtualFileSystem::Node>&& vnode)
     : m_vnode(move(vnode))

VirtualFileSystem/UnixTypes.h

@@ -8,6 +8,11 @@ namespace Unix {
 #define SEEK_CUR 1
 #define SEEK_END 2
 
+#define SIGINT 2
+#define SIGKILL 9
+#define SIGSEGV 11
+#define SIGTERM 15
+
 typedef dword dev_t;
 typedef dword ino_t;
 typedef dword mode_t;

VirtualFileSystem/VirtualFileSystem.cpp

@@ -558,11 +558,13 @@ InodeIdentifier VirtualFileSystem::resolvePath(const String& path, int& error, I
 
 void VirtualFileSystem::Node::retain()
 {
+    InterruptDisabler disabler; // FIXME: Make a Retainable with atomic retain count instead.
     ++retainCount;
 }
 
 void VirtualFileSystem::Node::release()
 {
+    InterruptDisabler disabler; // FIXME: Make a Retainable with atomic retain count instead.
     ASSERT(retainCount);
     if (--retainCount == 0) {
         m_vfs->freeNode(this);