Kernel/Userland: Add a halt syscall, and a shutdown binary to invoke it

Author: https://github.com/rburchell
Commit: https://github.com/SerenityOS/serenity/commit/952382b4134
Pull-request: https://github.com/SerenityOS/serenity/pull/232
Reviewed-by: https://github.com/awesomekling

Kernel/FileSystem/FileSystem.cpp

@@ -68,3 +68,11 @@ void FS::sync()
     for (auto fs : fses)
         fs->flush_writes();
 }
+
+void FS::lock_all()
+{
+    for (auto& it : all_fses()) {
+        it.value->m_lock.lock();
+    }
+}
+

Kernel/FileSystem/FileSystem.h

@@ -32,6 +32,7 @@ public:
     unsigned fsid() const { return m_fsid; }
     static FS* from_fsid(dword);
     static void sync();
+    static void lock_all();
 
     virtual bool initialize() = 0;
     virtual const char* class_name() const = 0;

Kernel/Syscall.cpp

@@ -1,6 +1,7 @@
 #include <Kernel/Arch/i386/CPU.h>
 #include <Kernel/Console.h>
 #include <Kernel/Process.h>
+#include <Kernel/IO.h>
 #include <Kernel/ProcessTracer.h>
 #include <Kernel/Scheduler.h>
 #include <Kernel/Syscall.h>
@@ -281,6 +282,15 @@ static dword handle(RegisterDump& regs, dword function, dword arg1, dword arg2,
         return current->process().sys$sched_setparam((pid_t)arg1, (struct sched_param*)arg2);
     case Syscall::SC_sched_getparam:
         return current->process().sys$sched_setparam((pid_t)arg1, (struct sched_param*)arg2);
+    case Syscall::SC_halt: {
+        dbgprintf("<%u> halting! acquiring locks...\n");
+        FS::lock_all();
+        dbgprintf("<%u> halting! syncing...\n");
+        FS::sync();
+        dbgprintf("<%u> halting! bye, friends...\n");
+        IO::out16(0x604, 0x2000);
+        break;
+    }
     default:
         kprintf("<%u> int0x82: Unknown function %u requested {%x, %x, %x}\n", current->process().pid(), function, arg1, arg2, arg3);
         return -ENOSYS;

Kernel/Syscall.h

@@ -112,7 +112,8 @@ struct timeval;
     __ENUMERATE_SYSCALL(getpeername)            \
     __ENUMERATE_SYSCALL(sched_setparam)         \
     __ENUMERATE_SYSCALL(sched_getparam)         \
-    __ENUMERATE_SYSCALL(fchown)
+    __ENUMERATE_SYSCALL(fchown)                 \
+    __ENUMERATE_SYSCALL(halt)
 
 namespace Syscall {
 

Userland/shutdown.cpp

@@ -0,0 +1,17 @@
+#include <Kernel/Syscall.h>
+#include <LibCore/CArgsParser.h>
+
+int main(int argc, char** argv)
+{
+    CArgsParser args_parser("shutdown");
+    args_parser.add_arg("n", "shut down now");
+    CArgsParserResult args = args_parser.parse(argc, (const char**)argv);
+
+    if (args.is_present("n")) {
+        syscall(SC_halt);
+        return 0;
+    } else {
+        args_parser.print_usage();
+        return 0;
+    }
+}