init: Add a configurable service system instead of always starting /bin/sh

apps/init.cpp

@@ -1,13 +1,23 @@
+#include <luna/PathParser.h>
+#include <luna/String.h>
+#include <luna/Vector.h>
+#include <os/File.h>
+#include <os/Process.h>
+
+#include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/sysmacros.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
+FILE* g_init_log;
+
 #define xmknod(path, mode, maj, min)                                                                                   \
     if (mknod(path, mode, makedev(maj, min)) < 0) exit(255);
 
@@ -23,6 +33,170 @@ static void populate_devfs()
     xmknod("/dev/fb0", 0222, 3, 0);
 }
 
+struct Service
+{
+    String name;
+    String command;
+    bool restart { false };
+    String environment;
+    Option<pid_t> pid {};
+};
+
+Vector<Service> g_services;
+
+static Result<void> service_child(const Service& service)
+{
+    auto args = TRY(service.command.split(" \n"));
+
+    if (service.environment.is_empty()) { TRY(os::Process::exec(args[0].view(), args.slice(), false)); }
+    else
+    {
+        auto env = TRY(service.environment.split(",\n"));
+        TRY(os::Process::exec(args[0].view(), args.slice(), env.slice(), false));
+    }
+
+    return {};
+}
+
+static Result<void> try_start_service(Service& service)
+{
+    pid_t pid = TRY(os::Process::fork());
+    if (pid == 0)
+    {
+        auto rc = service_child(service);
+        if (rc.has_error())
+        {
+            fprintf(g_init_log, "[child %d] failed to start service %s due to error: %s\n", getpid(),
+                    service.name.chars(), rc.error_string());
+        }
+        fclose(g_init_log);
+        exit(127);
+    }
+
+    fprintf(g_init_log, "[init] created new child process %d for service %s\n", pid, service.name.chars());
+
+    service.pid = pid;
+
+    return {};
+}
+
+static void start_service(Service& service)
+{
+    auto rc = try_start_service(service);
+    if (rc.has_error())
+    {
+        fprintf(g_init_log, "[init] failed to start service %s due to error: %s\n", service.name.chars(),
+                rc.error_string());
+    }
+}
+
+static Result<void> load_service(StringView path)
+{
+    fprintf(g_init_log, "[init] reading service file: %s\n", path.chars());
+
+    auto file = TRY(os::File::open(path, os::File::ReadOnly));
+
+    Service service;
+
+    while (true)
+    {
+        auto line = TRY(file->read_line(false));
+        if (line.is_empty()) break;
+
+        auto parts = TRY(line.split_once('='));
+        if (parts.size() < 2 || parts[0].is_empty() || parts[1].is_empty())
+        {
+            fprintf(g_init_log, "[init] file contains invalid line, aborting: '%s'\n", line.chars());
+            return {};
+        }
+
+        if (parts[0].view() == "Name")
+        {
+            service.name = move(parts[1]);
+            continue;
+        }
+
+        if (parts[0].view() == "Command")
+        {
+            service.command = move(parts[1]);
+            continue;
+        }
+
+        if (parts[0].view() == "Restart")
+        {
+            if (parts[1].view() == "true" || parts[1].view().to_uint().value_or(0) == 1)
+            {
+                service.restart = true;
+                continue;
+            }
+            service.restart = false;
+            continue;
+        }
+
+        if (parts[0].view() == "Environment")
+        {
+            service.environment = move(parts[1]);
+            continue;
+        }
+
+        fprintf(g_init_log, "[init] skipping unknown entry name %s\n", parts[0].chars());
+        continue;
+    }
+
+    if (service.name.is_empty())
+    {
+        fprintf(g_init_log, "[init] service file is missing 'Name' entry, aborting!\n");
+        return {};
+    }
+
+    if (service.command.is_empty())
+    {
+        fprintf(g_init_log, "[init] service file is missing 'Command' entry, aborting!\n");
+        return {};
+    }
+
+    fprintf(g_init_log, "[init] loaded service %s into memory\n", service.name.chars());
+
+    TRY(g_services.try_append(move(service)));
+
+    return {};
+}
+
+static Result<void> load_services()
+{
+    DIR* dp = opendir("/etc/init");
+    if (!dp)
+    {
+        fprintf(g_init_log, "[init] cannot open service directory: %s\n", strerror(errno));
+        return {};
+    }
+
+    dirent* ent;
+    while ((ent = readdir(dp)))
+    {
+        if ("."_sv == ent->d_name || ".."_sv == ent->d_name) continue;
+
+        auto service_path = TRY(PathParser::join("/etc/init"_sv, ent->d_name));
+        TRY(load_service(service_path.view()));
+    }
+
+    closedir(dp);
+
+    return {};
+}
+
+static Result<void> start_services()
+{
+    TRY(load_services());
+    for (auto& service : g_services)
+    {
+        fprintf(g_init_log, "[init] starting service %s\n", service.name.chars());
+        start_service(service);
+    }
+
+    return {};
+}
+
 int main()
 {
     if (getpid() != 1)
@@ -39,16 +213,32 @@ int main()
     stdout = fopen("/dev/console", "w");
     stderr = fopen("/dev/console", "w");
 
-    pid_t ret = fork();
+    g_init_log = fopen("/init.log", "w+");
+    fcntl(fileno(g_init_log), F_SETFD, FD_CLOEXEC);
 
-    if (ret == 0)
+    start_services();
+
+    while (1)
     {
-        char* argv[] = { "/bin/sh", NULL };
-        char* envp[] = { "PATH=/bin:/sbin", NULL };
-        execve(argv[0], argv, envp);
-        perror("execv");
-        return 1;
-    }
+        int status;
+        pid_t child = wait(&status);
 
-    while (1) wait(NULL);
+        for (auto& service : g_services)
+        {
+            if (service.pid.has_value() && service.pid.value() == child)
+            {
+                fprintf(g_init_log, "[init] service %s exited with status %d\n", service.name.chars(),
+                        WEXITSTATUS(status));
+
+                if (service.restart)
+                {
+                    fprintf(g_init_log, "[init] restarting service %s\n", service.name.chars());
+
+                    start_service(service);
+                }
+
+                break;
+            }
+        }
+    }
 }

initrd/etc/init/99-shell

@@ -0,0 +1,4 @@
+Name=shell
+Command=/bin/sh
+Restart=true
+Environment=PATH=/bin:/sbin