From cde467ee465cd821a71f068bfd89a6f6100d0175 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Mon, 10 Jul 2023 20:16:06 +0200
Subject: [PATCH] kernel: Support returning termination signals from waitpid

---
 apps/init.cpp                |  9 ++++++++-
 kernel/src/sys/signal.cpp    |  2 +-
 kernel/src/thread/Thread.cpp | 12 ++++++++++--
 kernel/src/thread/Thread.h   |  6 ++++--
 libc/include/bits/waitpid.h  |  2 ++
 libc/include/sys/wait.h      |  4 +++-
 6 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/apps/init.cpp b/apps/init.cpp
index 4f5d268a..131c2166 100644
--- a/apps/init.cpp
+++ b/apps/init.cpp
@@ -328,7 +328,14 @@ int main()
         {
             if (service.pid.has_value() && service.pid.value() == child)
             {
-                do_log("[init] service %s exited with status %d\n", service.name.chars(), WEXITSTATUS(status));
+                if (WIFEXITED(status))
+                {
+                    do_log("[init] service %s exited with status %d\n", service.name.chars(), WEXITSTATUS(status));
+                }
+                else
+                {
+                    do_log("[init] service %s was terminated by signal %d\n", service.name.chars(), WTERMSIG(status));
+                }
 
                 if (service.restart)
                 {
diff --git a/kernel/src/sys/signal.cpp b/kernel/src/sys/signal.cpp
index a0bfdd36..864fd1f8 100644
--- a/kernel/src/sys/signal.cpp
+++ b/kernel/src/sys/signal.cpp
@@ -62,7 +62,7 @@ Result<u64> sys_kill(Registers*, SyscallArgs args)
     if (target->is_kernel) return 0;
     if (signo == 0) return 0;
 
-    target->pending_signals |= 1 << (signo - 1);
+    target->send_signal(signo);
 
     return 0;
 }
diff --git a/kernel/src/thread/Thread.cpp b/kernel/src/thread/Thread.cpp
index 1e17f89c..6031fc55 100644
--- a/kernel/src/thread/Thread.cpp
+++ b/kernel/src/thread/Thread.cpp
@@ -4,6 +4,7 @@
 #include "thread/Scheduler.h"
 #include <bits/atfile.h>
 #include <bits/open-flags.h>
+#include <bits/waitpid.h>
 #include <luna/Alloc.h>
 #include <luna/Atomic.h>
 #include <luna/PathParser.h>
@@ -70,7 +71,7 @@ Result<SharedPtr<VFS::Inode>> Thread::resolve_atfile(int dirfd, const String& pa
     return VFS::resolve_path(path.chars(), this->auth, descriptor->inode, follow_last_symlink);
 }
 
-[[noreturn]] void Thread::exit_and_signal_parent(u8 _status)
+[[noreturn]] void Thread::exit_and_signal_parent(int _status)
 {
     if (this->id == 1) fail("the init process exited");
     if (is_kernel) state = ThreadState::Dying;
@@ -140,7 +141,8 @@ void Thread::process_pending_signals(Registers* current_regs)
                 {
                 case DefaultSignalAction::Ignore: return;
                 // FIXME: Add signal exit codes.
-                case DefaultSignalAction::Terminate: exit_and_signal_parent(255);
+                case DefaultSignalAction::Terminate: exit_and_signal_parent(signo | _SIGBIT);
+                default: return;
                 }
             }
             // If we fail to deliver the signal (usually because there's not enough space on the stack), execute the
@@ -151,6 +153,12 @@ void Thread::process_pending_signals(Registers* current_regs)
     }
 }
 
+void Thread::send_signal(int signo)
+{
+    check(signo > 0 && signo <= NSIG);
+    pending_signals |= 1 << (signo - 1);
+}
+
 bool FileDescriptor::should_append()
 {
     return flags & O_APPEND;
diff --git a/kernel/src/thread/Thread.h b/kernel/src/thread/Thread.h
index e568bb44..be90fab1 100644
--- a/kernel/src/thread/Thread.h
+++ b/kernel/src/thread/Thread.h
@@ -91,7 +91,7 @@ struct Thread : public LinkedListNode<Thread>
 
     bool is_kernel { true };
 
-    u8 status { 0 };
+    int status { 0 };
 
     mode_t umask { 0 };
 
@@ -110,7 +110,7 @@ struct Thread : public LinkedListNode<Thread>
 
     PageDirectory* active_directory { nullptr };
 
-    [[noreturn]] void exit_and_signal_parent(u8 status);
+    [[noreturn]] void exit_and_signal_parent(int status);
 
     bool is_idle()
     {
@@ -144,6 +144,8 @@ struct Thread : public LinkedListNode<Thread>
     Result<u64> push_mem_on_stack(const u8* mem, usize size);
     Result<u64> pop_mem_from_stack(u8* mem, usize size);
 
+    void send_signal(int signo);
+
     static void init();
 };
 
diff --git a/libc/include/bits/waitpid.h b/libc/include/bits/waitpid.h
index 8b7922b4..2ed3b15e 100644
--- a/libc/include/bits/waitpid.h
+++ b/libc/include/bits/waitpid.h
@@ -3,6 +3,8 @@
 #ifndef _BITS_WAITPID_H
 #define _BITS_WAITPID_H
 
+#define _SIGBIT 0x100
+
 #define WNOHANG 1
 
 #endif
diff --git a/libc/include/sys/wait.h b/libc/include/sys/wait.h
index 4fa9c3e5..a10d9bf1 100644
--- a/libc/include/sys/wait.h
+++ b/libc/include/sys/wait.h
@@ -6,8 +6,10 @@
 #include <bits/waitpid.h>
 #include <sys/types.h>
 
-#define WIFEXITED(ret) ((ret) | 0)
+#define WIFEXITED(ret) (((ret)&_SIGBIT) == 0)
 #define WEXITSTATUS(ret) ((ret)&0xff)
+#define WIFSIGNALED(ret) (((ret)&_SIGBIT) == _SIGBIT)
+#define WTERMSIG(ret) ((ret)&0xff)
 
 #ifdef __cplusplus
 extern "C"