init: Add a few more configuration options for services

Notably, redirecting a service's standard streams and waiting for a service to finish before continuing boot.

apps/init.cpp

@@ -39,15 +39,24 @@ struct Service
     String command;
     bool restart { false };
     String environment;
+    String standard_output;
+    String standard_error;
+    String standard_input;
+    bool wait { false };
     Option<pid_t> pid {};
 };
 
 Vector<Service> g_services;
 
-static Result<void> service_child(const Service& service)
+static Result<void> service_child(const Service& service, SharedPtr<os::File> output, SharedPtr<os::File> error,
+                                  SharedPtr<os::File> input)
 {
     auto args = TRY(service.command.split(" \n"));
 
+    if (output) dup2(output->fd(), STDOUT_FILENO);
+    if (error) dup2(error->fd(), STDERR_FILENO);
+    if (input) dup2(input->fd(), STDIN_FILENO);
+
     if (service.environment.is_empty()) { TRY(os::Process::exec(args[0].view(), args.slice(), false)); }
     else
     {
@@ -60,10 +69,32 @@ static Result<void> service_child(const Service& service)
 
 static Result<void> try_start_service(Service& service)
 {
+    SharedPtr<os::File> new_stdout = {};
+    SharedPtr<os::File> new_stderr = {};
+    SharedPtr<os::File> new_stdin = {};
+
+    if (!service.standard_output.is_empty())
+    {
+        new_stdout = TRY(os::File::open_or_create(service.standard_output.view(), os::File::Append, 0600));
+        new_stdout->set_close_on_exec();
+    }
+
+    if (!service.standard_error.is_empty())
+    {
+        new_stderr = TRY(os::File::open_or_create(service.standard_error.view(), os::File::Append, 0600));
+        new_stderr->set_close_on_exec();
+    }
+
+    if (!service.standard_input.is_empty())
+    {
+        new_stdin = TRY(os::File::open(service.standard_input.view(), os::File::ReadOnly));
+        new_stdin->set_close_on_exec();
+    }
+
     pid_t pid = TRY(os::Process::fork());
     if (pid == 0)
     {
-        auto rc = service_child(service);
+        auto rc = service_child(service, new_stdout, new_stderr, new_stdin);
         if (rc.has_error())
         {
             fprintf(g_init_log, "[child %d] failed to start service %s due to error: %s\n", getpid(),
@@ -75,7 +106,18 @@ static Result<void> try_start_service(Service& service)
 
     fprintf(g_init_log, "[init] created new child process %d for service %s\n", pid, service.name.chars());
 
-    service.pid = pid;
+    if (service.wait)
+    {
+        fprintf(g_init_log, "[init] waiting for child process %d to finish\n", pid);
+
+        int status;
+        pid_t id = waitpid(pid, &status, 0);
+        if (id < 0) { return err(errno); }
+
+        fprintf(g_init_log, "[init] child process %d exited with code %d\n", pid, WEXITSTATUS(status));
+    }
+    else
+        service.pid = pid;
 
     return {};
 }
@@ -142,6 +184,35 @@ static Result<void> load_service(StringView path)
             continue;
         }
 
+        if (parts[0].view() == "StandardOutput")
+        {
+            service.standard_output = move(parts[1]);
+            continue;
+        }
+
+        if (parts[0].view() == "StandardError")
+        {
+            service.standard_error = move(parts[1]);
+            continue;
+        }
+
+        if (parts[0].view() == "StandardInput")
+        {
+            service.standard_input = move(parts[1]);
+            continue;
+        }
+
+        if (parts[0].view() == "Wait")
+        {
+            if (parts[1].view() == "true" || parts[1].view().to_uint().value_or(0) == 1)
+            {
+                service.wait = true;
+                continue;
+            }
+            service.wait = false;
+            continue;
+        }
+
         fprintf(g_init_log, "[init] skipping unknown entry name %s\n", parts[0].chars());
     }
 

libos/include/os/File.h

@@ -39,6 +39,11 @@ namespace os
 
         Result<int> getchar();
 
+        int fd() const
+        {
+            return m_fd;
+        }
+
         File(Badge<File>);
         ~File();