Kernel: Support signaling all processes with pid == -1

This is a special case that was previously not implemented.
The idea is that you can dispatch a signal to all other processes
the calling process has access to.

There was some minor refactoring to make the self signal logic
into a function so it could easily be easily re-used from do_killall.

Kernel/Process.cpp

@@ -2219,6 +2219,45 @@ KResult Process::do_killpg(pid_t pgrp, int signal)
  return error;
 }
 
+KResult Process::do_killall(int signal)
+{
+ InterruptDisabler disabler;
+
+ bool any_succeeded = false;
+ KResult error = KSuccess;
+
+ // Send the signal to all processes we have access to for.
+ for (auto& process : *g_processes) {
+ KResult res = KSuccess;
+ if (process.pid() == m_pid)
+ res = do_killself(signal);
+ else
+ res = do_kill(process, signal);
+
+ if (res.is_success())
+ any_succeeded = true;
+ else
+ error = res;
+ }
+
+ if (any_succeeded)
+ return KSuccess;
+ return error;
+}
+
+KResult Process::do_killself(int signal)
+{
+ if (signal == 0)
+ return KSuccess;
+
+ if (!Thread::current->should_ignore_signal(signal)) {
+ Thread::current->send_signal(signal, this);
+ (void)Thread::current->block<Thread::SemiPermanentBlocker>(Thread::SemiPermanentBlocker::Reason::Signal);
+ }
+
+ return KSuccess;
+}
+
 int Process::sys$kill(pid_t pid, int signal)
 {
  if (pid == m_pid)
@@ -2228,23 +2267,15 @@ int Process::sys$kill(pid_t pid, int signal)
 
  if (signal < 0 || signal >= 32)
  return -EINVAL;
- if (pid <= 0) {
+ if (pid < -1) {
  if (pid == INT32_MIN)
  return -EINVAL;
  return do_killpg(-pid, signal);
  }
- if (pid == -1) {
- // FIXME: Send to all processes.
- return -ENOTIMPL;
- }
+ if (pid == -1)
+ return do_killall(signal);
  if (pid == m_pid) {
- if (signal == 0)
- return 0;
- if (!Thread::current->should_ignore_signal(signal)) {
- Thread::current->send_signal(signal, this);
- (void)Thread::current->block<Thread::SemiPermanentBlocker>(Thread::SemiPermanentBlocker::Reason::Signal);
- }
- return 0;
+ return do_killself(signal);
  }
  InterruptDisabler disabler;
  auto* peer = Process::from_pid(pid);

Kernel/Process.h

@@ -445,6 +445,8 @@ class Process : public InlineLinkedListNode<Process> {
 
  KResult do_kill(Process&, int signal);
  KResult do_killpg(pid_t pgrp, int signal);
+ KResult do_killall(int signal);
+ KResult do_killself(int signal);
 
  KResultOr<siginfo_t> do_waitid(idtype_t idtype, int id, int options);